mmc: add an ioctl for erasing

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From: Christoph Hellwig on 21 May 2010 10:10

---

On Fri, May 21, 2010 at 04:47:40PM +0300, Adrian Hunter wrote:
>> From f3baf566eb33a22bf12a48e4cdc7c99611bde934 Mon Sep 17 00:00:00 2001
> From: Adrian Hunter <adrian.hunter(a)nokia.com>
> Date: Wed, 5 May 2010 14:07:55 +0300
> Subject: [PATCH] mmc: add an ioctl for erasing
>
> As SD and MMC cards have a NAND core, they can support an erase
> operation that is typically 10x to 100x faster than writing.
>
> In addition, eMMCv4.4 also offers:
> o Secure Erase
> o Trim
> o Secure Trim
>
> The "secure" variants also ensure that any copies of the data
> (for example remnants of garbage collection) are also erased.
>
> "Trim" is the same as "erase" except that individual sectors
> can be erased instead of whole Erase Groups.
>
> The Erase Operation and its variants are not supported by
> default and drivers must set MMC_CAP_ERASE. This is because
> the operation can take a long time and drivers that rely on
> polling the status may perform very badly. Also drivers
> may need changes to support the very long erase timeouts.

Please don't add new device specific ioctls. Just implement the
block layer discard operation to make the discard ioctl work on MMC
device. We can talk about adding a secure erase variant of it then.

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From: George G. Davis on 25 May 2010 21:10

---

Hi,

On Fri, May 21, 2010 at 04:47:40PM +0300, Adrian Hunter wrote:
> >From f3baf566eb33a22bf12a48e4cdc7c99611bde934 Mon Sep 17 00:00:00 2001
> From: Adrian Hunter <adrian.hunter(a)nokia.com>
> Date: Wed, 5 May 2010 14:07:55 +0300
> Subject: [PATCH] mmc: add an ioctl for erasing
>
> As SD and MMC cards have a NAND core, they can support an erase
> operation that is typically 10x to 100x faster than writing.
>
> In addition, eMMCv4.4 also offers:
> o Secure Erase
> o Trim
> o Secure Trim

As already noted by others, getting SD/MMC card trim properly implemented
to support block discard requests would be a good thing and I'm willing
to help with getting that implemented.

Thanks!

--
Regards,
George

>
> The "secure" variants also ensure that any copies of the data
> (for example remnants of garbage collection) are also erased.
>
> "Trim" is the same as "erase" except that individual sectors
> can be erased instead of whole Erase Groups.
>
> The Erase Operation and its variants are not supported by
> default and drivers must set MMC_CAP_ERASE. This is because
> the operation can take a long time and drivers that rely on
> polling the status may perform very badly. Also drivers
> may need changes to support the very long erase timeouts.
>
> Signed-off-by: Adrian Hunter <adrian.hunter(a)nokia.com>
> ---
> Documentation/ioctl/ioctl-number.txt | 1 +
> drivers/mmc/card/block.c | 159 +++++++++++++++++
> drivers/mmc/core/core.c | 323 ++++++++++++++++++++++++++++++++++
> drivers/mmc/core/core.h | 2 +
> drivers/mmc/core/mmc.c | 43 +++++-
> drivers/mmc/core/sd.c | 80 +++++++++
> drivers/mmc/core/sd_ops.c | 48 +++++
> drivers/mmc/core/sd_ops.h | 1 +
> include/linux/Kbuild | 1 +
> include/linux/mmc/Kbuild | 1 +
> include/linux/mmc/card.h | 19 ++
> include/linux/mmc/core.h | 17 ++
> include/linux/mmc/host.h | 1 +
> include/linux/mmc/mmc.h | 24 ++-
> include/linux/mmc/mmc_ioctl.h | 63 +++++++
> include/linux/mmc/sd.h | 5 +
> 16 files changed, 781 insertions(+), 7 deletions(-)
> create mode 100644 include/linux/mmc/Kbuild
> create mode 100644 include/linux/mmc/mmc_ioctl.h
>
> diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
> index dd5806f..10ae568 100644
> --- a/Documentation/ioctl/ioctl-number.txt
> +++ b/Documentation/ioctl/ioctl-number.txt
> @@ -308,6 +308,7 @@ Code Seq#(hex) Include File Comments
> 0xB0 all RATIO devices in development:
> <mailto:vgo(a)ratio.de>
> 0xB1 00-1F PPPoX <mailto:mostrows(a)styx.uwaterloo.ca>
> +0xB3 00-1F linux/mmc/mmc_ioctl.h
> 0xC0 00-0F linux/usb/iowarrior.h
> 0xCB 00-1F CBM serial IEC bus in development:
> <mailto:michael.klein(a)puffin.lb.shuttle.de>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index cb9fbc8..6a386af 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -31,11 +31,13 @@
> #include <linux/mutex.h>
> #include <linux/scatterlist.h>
> #include <linux/string_helpers.h>
> +#include <linux/delay.h>
>
> #include <linux/mmc/card.h>
> #include <linux/mmc/host.h>
> #include <linux/mmc/mmc.h>
> #include <linux/mmc/sd.h>
> +#include <linux/mmc/mmc_ioctl.h>
>
> #include <asm/system.h>
> #include <asm/uaccess.h>
> @@ -138,9 +140,166 @@ mmc_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
> return 0;
> }
>
> +static int check_eod(struct block_device *bdev, unsigned int from,
> + unsigned int nr)
> +{
> + unsigned int maxsector;
> +
> + if (!nr)
> + return 0;
> +
> + maxsector = bdev->bd_inode->i_size >> 9;
> + if (maxsector && (maxsector < nr || maxsector - nr < from))
> + return 1;
> +
> + return 0;
> +}
> +
> +static int mmc_blk_erase(struct mmc_blk_data *md, unsigned int from,
> + unsigned int nr, unsigned int flag)
> +{
> + struct mmc_card *card = md->queue.card;
> + struct request_queue *q = md->queue.queue;
> + unsigned int n, arg;
> + int i, ok, err;
> +
> + switch (flag) {
> + case MMC_ERASE_FLAG:
> + arg = MMC_ERASE_ARG;
> + break;
> + case MMC_SECURE_ERASE_FLAG:
> + arg = MMC_SECURE_ERASE_ARG;
> + break;
> + case MMC_TRIM_FLAG:
> + arg = MMC_TRIM_ARG;
> + break;
> + case MMC_SECURE_TRIM1_FLAG:
> + arg = MMC_SECURE_TRIM1_ARG;
> + break;
> + case MMC_SECURE_TRIM2_FLAG:
> + arg = MMC_SECURE_TRIM2_ARG;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + mmc_claim_host(card->host);
> + n = card->max_erase - (from % card->max_erase);
> + do {
> + /*
> + * Do not allow the MMCERASE ioctl to have priority over
> + * scheduled I/O.
> + */
> + for (i = 0; i < 40; i++) {
> + spin_lock_irq(q->queue_lock);
> + ok = elv_queue_empty(q);
> + spin_unlock_irq(q->queue_lock);
> + if (ok)
> + break;
> + mmc_release_host(card->host);
> + msleep(50);
> + mmc_claim_host(card->host);
> + }
> + if (n > nr)
> + n = nr;
> + err = mmc_erase(card, from, n, arg);
> + if (err)
> + break;
> + from += n;
> + nr -= n;
> + n = card->max_erase;
> + } while (nr);
> + mmc_release_host(card->host);
> +
> + return err;
> +}
> +
> +static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
> + unsigned cmd, unsigned long arg)
> +{
> + struct mmc_blk_data *md = bdev->bd_disk->private_data;
> +
> + switch (cmd) {
> + case MMCERASEINFO: {
> + struct mmc_blk_erase_info info;
> + struct mmc_card *card = md->queue.card;
> + unsigned int flags = 0;
> +
> + if (!arg)
> + return -EINVAL;
> +
> + mmc_claim_host(card->host);
> + info.erase_size = card->erase_size;
> + if (mmc_can_erase(card)) {
> + flags |= MMC_ERASE_FLAG;
> + if (mmc_can_secure_erase_trim(card))
> + flags |= MMC_SECURE_ERASE_FLAG;
> + if (mmc_can_trim(card)) {
> + flags |= MMC_TRIM_FLAG;
> + if (mmc_can_secure_erase_trim(card)) {
> + flags |= MMC_SECURE_TRIM1_FLAG;
> + flags |= MMC_SECURE_TRIM2_FLAG;
> + }
> + }
> + }
> + info.flags = flags;
> + info.erased_byte = card->erased_byte;
> + mmc_release_host(card->host);
> +
> + if (copy_to_user((struct mmc_blk_erase_info __user *)arg, &info,
> + sizeof(struct mmc_blk_erase_info)))
> + return -EFAULT;
> +
> + return 0;
> + }
> + case MMCERASE: {
> + struct mmc_blk_erase_args args;
> +
> + if (!(mode & FMODE_WRITE))
> + return -EBADF;
> +
> + if (copy_from_user(&args, (void __user *)arg,
> + sizeof(struct mmc_blk_erase_args)))
> + return -EFAULT;
> +
> + if (check_eod(bdev, args.from, args.nr))
> + return -EINVAL;
> +
> + if (bdev != bdev->bd_contains)
> + args.from += bdev->bd_part->start_sect;
> +
> + return mmc_blk_erase(md, args.from, args.nr, args.flag);
> + }
> + }
> + return -ENOTTY;
> +}
> +
> +#ifdef CONFIG_COMPAT
> +
> +static int mmc_blk_compat_ioctl(struct block_device *bdev, fmode_t mode,
> + unsigned cmd, unsigned long arg)
> +{
> + switch (cmd) {
> + case MMCERASEINFO:
> + case MMCERASE:
> + break;
> + default:
> + return -ENOIOCTLCMD;
> + }
> + return mmc_blk_ioctl(bdev, mode, cmd, arg);
> +}
> +
> +#else
> +
> +#define mmc_blk_compat_ioctl NULL
> +
> +#endif
> +
> static const struct block_device_operations mmc_bdops = {
> .open = mmc_blk_open,
> .release = mmc_blk_release,
> + .ioctl = mmc_blk_ioctl,
> + .compat_ioctl = mmc_blk_compat_ioctl,
> .getgeo = mmc_blk_getgeo,
> .owner = THIS_MODULE,
> };
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 3168ebd..f32cc2d 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1050,6 +1050,329 @@ void mmc_detect_change(struct mmc_host *host, unsigned long delay)
>
> EXPORT_SYMBOL(mmc_detect_change);
>
> +void mmc_init_erase(struct mmc_card *card)
> +{
> + unsigned int sz;
> +
> + if (is_power_of_2(card->erase_size) && card->erase_size > 512)
> + card->erase_shift = ffs(card->erase_size) - 10;
> + else
> + card->erase_shift = 0;
> +
> + /*
> + * It is possible to erase an arbitrarily large area of an SD or MMC
> + * card. That is not desirable because it can take a long time
> + * (minutes) potentially delaying more important I/O, and also the
> + * timeout calculations become increasingly hugely over-estimated.
> + * Consequently, 'max_erase' is defined as a guide to upper layers
> + * (i.e. the MMC Block driver) to limit erases to that size and
> + * alignment.
> + *
> + * For SD cards that define Allocation Unit size, limit erases to one
> + * Allocation Unit at a time. For MMC cards that define High Capacity
> + * Erase Size, whether it is switched on or not, limit to that size.
> + * Otherwise just have a stab at a good value. For modern cards it
> + * will end up being 4MiB. Note that if the value is too small, it
> + * can end up taking longer to erase.
> + */
> + if (mmc_card_sd(card) && card->ssr.au) {
> + card->max_erase = card->ssr.au;
> + card->erase_shift = ffs(card->ssr.au) - 1;
> + } else if (card->ext_csd.hc_erase_size) {
> + card->max_erase = card->ext_csd.hc_erase_size >> 9;
> + } else {
> + sz = (card->csd.capacity << (card->csd.read_blkbits - 9)) >> 11;
> + if (sz < 128)
> + card->max_erase = 512 * 1024;
> + else if (sz < 512)
> + card->max_erase = 1024 * 1024;
> + else if (sz < 1024)
> + card->max_erase = 2 * 1024 * 1024;
> + else
> + card->max_erase = 4 * 1024 * 1024;
> + if (card->max_erase < card->erase_size)
> + card->max_erase = card->erase_size;
> + else {
> + sz = card->max_erase % card->erase_size;
> + if (sz)
> + card->max_erase += card->erase_size - sz;
> + }
> + card->max_erase >>= 9;
> + }
> +}
> +
> +static void mmc_set_mmc_erase_timeout(struct mmc_card *card,
> + struct mmc_command *cmd,
> + unsigned int arg, unsigned int qty)
> +{
> + unsigned int erase_timeout;
> +
> + if (card->ext_csd.erase_group_def & 1) {
> + /* High Capacity Erase Group Size uses HC timeouts */
> + if (arg == MMC_TRIM_ARG)
> + erase_timeout = card->ext_csd.trim_timeout;
> + else
> + erase_timeout = card->ext_csd.hc_erase_timeout;
> + } else {
> + /* CSD Erase Group Size uses write timeout */
> + unsigned int mult = (10 << card->csd.r2w_factor);
> + unsigned int timeout_clks = card->csd.tacc_clks * mult;
> + unsigned int timeout_us;
> +
> + /* Avoid overflow: e.g. tacc_ns=80000000 mult=1280 */
> + if (card->csd.tacc_ns < 1000000)
> + timeout_us = (card->csd.tacc_ns * mult) / 1000;
> + else
> + timeout_us = (card->csd.tacc_ns / 1000) * mult;
> +
> + /*
> + * ios.clock is only a target. The real clock rate might be
> + * less but not that much less, so fudge it by multiplying by 2.
> + */
> + timeout_clks <<= 1;
> + timeout_us += (timeout_clks * 1000) /
> + (card->host->ios.clock / 1000);
> +
> + erase_timeout = timeout_us / 1000;
> +
> + /*
> + * Theoretically, the calculation could underflow so round up
> + * to 1ms in that case.
> + */
> + if (!erase_timeout)
> + erase_timeout = 1;
> + }
> +
> + /* Multiplier for secure operations */
> + if (arg & MMC_SECURE_ARGS) {
> + if (arg == MMC_SECURE_ERASE_ARG)
> + erase_timeout *= card->ext_csd.sec_erase_mult;
> + else
> + erase_timeout *= card->ext_csd.sec_trim_mult;
> + }
> +
> + erase_timeout *= qty;
> +
> + /*
> + * Ensure at least a 1 second timeout for SPI as per
> + * 'mmc_set_data_timeout()'
> + */
> + if (mmc_host_is_spi(card->host) && erase_timeout < 1000)
> + erase_timeout = 1000;
> +
> + cmd->erase_timeout = erase_timeout;
> +}
> +
> +static void mmc_set_sd_erase_timeout(struct mmc_card *card,
> + struct mmc_command *cmd, unsigned int arg,
> + unsigned int qty)
> +{
> + if (card->ssr.erase_timeout) {
> + /* Erase timeout specified in SD Status Register (SSR) */
> + cmd->erase_timeout = card->ssr.erase_timeout * qty +
> + card->ssr.erase_offset;
> + } else {
> + /*
> + * Erase timeout not specified in SD Status Register (SSR) so
> + * use 250ms per write block.
> + */
> + cmd->erase_timeout = 250 * qty;
> + }
> +
> + /* Must not be less than 1 second */
> + if (cmd->erase_timeout < 1000)
> + cmd->erase_timeout = 1000;
> +}
> +
> +static void mmc_set_erase_timeout(struct mmc_card *card,
> + struct mmc_command *cmd, unsigned int arg,
> + unsigned int qty)
> +{
> + if (mmc_card_sd(card))
> + mmc_set_sd_erase_timeout(card, cmd, arg, qty);
> + else
> + mmc_set_mmc_erase_timeout(card, cmd, arg, qty);
> +}
> +
> +static int mmc_do_erase(struct mmc_card *card, unsigned int from,
> + unsigned int to, unsigned int arg)
> +{
> + struct mmc_command cmd;
> + unsigned int qty = 0;
> + int err;
> +
> + /*
> + * qty is used to calculate the erase timeout which depends on how many
> + * erase groups (or allocation units in SD terminology) are affected.
> + * We count erasing part of an erase group as one erase group.
> + * For SD, the allocation units are always a power of 2. For MMC, the
> + * erase group size is almost certainly also power of 2, but it does not
> + * seem to insist on that in the JEDEC standard, so we fall back to
> + * division in that case. SD may not specify an allocation unit size,
> + * in which case the timeout is based on the number of write blocks.
> + *
> + * Note that the timeout for secure trim 2 will only be correct if the
> + * number of erase groups specified is the same as the total of all
> + * preceding secure trim 1 commands. Since the power may have been
> + * lost since the secure trim 1 commands occurred, it is generally
> + * impossible to calculate the secure trim 2 timeout correctly.
> + */
> + if (card->erase_shift)
> + qty += ((to >> card->erase_shift) -
> + (from >> card->erase_shift)) + 1;
> + else if (mmc_card_sd(card))
> + qty += to - from + 1;
> + else
> + qty += ((to / (card->erase_size >> 9)) -
> + (from / (card->erase_size >> 9))) + 1;
> +
> + if (!mmc_card_blockaddr(card)) {
> + from <<= 9;
> + to <<= 9;
> + }
> +
> + memset(&cmd, 0, sizeof(struct mmc_command));
> + if (mmc_card_sd(card))
> + cmd.opcode = SD_ERASE_WR_BLK_START;
> + else
> + cmd.opcode = MMC_ERASE_GROUP_START;
> + cmd.arg = from;
> + cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC;
> + err = mmc_wait_for_cmd(card->host, &cmd, 0);
> + if (err) {
> + printk(KERN_ERR "mmc_erase: group start error %d, "
> + "status %#x\n", err, cmd.resp[0]);
> + err = -EINVAL;
> + goto out;
> + }
> +
> + memset(&cmd, 0, sizeof(struct mmc_command));
> + if (mmc_card_sd(card))
> + cmd.opcode = SD_ERASE_WR_BLK_END;
> + else
> + cmd.opcode = MMC_ERASE_GROUP_END;
> + cmd.arg = to;
> + cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_AC;
> + err = mmc_wait_for_cmd(card->host, &cmd, 0);
> + if (err) {
> + printk(KERN_ERR "mmc_erase: group end error %d, status %#x\n",
> + err, cmd.resp[0]);
> + err = -EINVAL;
> + goto out;
> + }
> +
> + memset(&cmd, 0, sizeof(struct mmc_command));
> + cmd.opcode = MMC_ERASE;
> + cmd.arg = arg;
> + cmd.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
> + mmc_set_erase_timeout(card, &cmd, arg, qty);
> + err = mmc_wait_for_cmd(card->host, &cmd, 0);
> + if (err) {
> + printk(KERN_ERR "mmc_erase: erase error %d, status %#x\n",
> + err, cmd.resp[0]);
> + err = -EIO;
> + goto out;
> + }
> +
> + if (mmc_host_is_spi(card->host))
> + goto out;
> +
> + do {
> + memset(&cmd, 0, sizeof(struct mmc_command));
> + cmd.opcode = MMC_SEND_STATUS;
> + cmd.arg = card->rca << 16;
> + cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
> + /* Do not retry else we can't see errors */
> + err = mmc_wait_for_cmd(card->host, &cmd, 0);
> + if (err || (cmd.resp[0] & 0xFDF92000)) {
> + printk(KERN_ERR "error %d requesting status %#x\n",
> + err, cmd.resp[0]);
> + err = -EIO;
> + goto out;
> + }
> + } while (!(cmd.resp[0] & R1_READY_FOR_DATA) ||
> + R1_CURRENT_STATE(cmd.resp[0]) == 7);
> +out:
> + return err;
> +}
> +
> +/**
> + * mmc_erase - erase sectors.
> + * @card: card to erase
> + * @from: first sector to erase
> + * @nr: number of sectors to erase
> + * @arg: erase command argument (SD supports only %MMC_ERASE_ARG)
> + *
> + * Caller must claim host before calling this function.
> + */
> +int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
> + unsigned int arg)
> +{
> + unsigned int erase_sects = card->erase_size >> 9, to = from + nr;
> +
> + if (!(card->host->caps & MMC_CAP_ERASE) ||
> + !(card->csd.cmdclass & CCC_ERASE))
> + return -EOPNOTSUPP;
> +
> + if ((card->erase_size & 511) || erase_sects == 0)
> + return -EOPNOTSUPP;
> +
> + if (mmc_card_sd(card) && arg != MMC_ERASE_ARG)
> + return -EOPNOTSUPP;
> +
> + if ((arg & MMC_SECURE_ARGS) &&
> + !(card->ext_csd.sec_feature_support & EXT_CSD_SEC_ER_EN))
> + return -EOPNOTSUPP;
> +
> + if ((arg & MMC_TRIM_ARGS) &&
> + !(card->ext_csd.sec_feature_support & EXT_CSD_SEC_GB_CL_EN))
> + return -EOPNOTSUPP;
> +
> + if (arg == MMC_ERASE_ARG || arg == MMC_SECURE_ERASE_ARG) {
> + if (erase_sects != 1 &&
> + (from % erase_sects != 0 || nr % erase_sects != 0))
> + return -EINVAL;
> + }
> +
> + if (nr == 0)
> + return 0;
> +
> + if (to <= from)
> + return -EINVAL;
> +
> + /* 'from' and 'to' are inclusive */
> + to -= 1;
> +
> + return mmc_do_erase(card, from, to, arg);
> +}
> +EXPORT_SYMBOL(mmc_erase);
> +
> +int mmc_can_erase(struct mmc_card *card)
> +{
> + if ((card->host->caps & MMC_CAP_ERASE) &&
> + (card->csd.cmdclass & CCC_ERASE) &&
> + card->erase_size &&
> + !(card->erase_size & 511))
> + return 1;
> + return 0;
> +}
> +EXPORT_SYMBOL(mmc_can_erase);
> +
> +int mmc_can_trim(struct mmc_card *card)
> +{
> + if (card->ext_csd.sec_feature_support & EXT_CSD_SEC_GB_CL_EN)
> + return 1;
> + return 0;
> +}
> +EXPORT_SYMBOL(mmc_can_trim);
> +
> +int mmc_can_secure_erase_trim(struct mmc_card *card)
> +{
> + if (card->ext_csd.sec_feature_support & EXT_CSD_SEC_ER_EN)
> + return 1;
> + return 0;
> +}
> +EXPORT_SYMBOL(mmc_can_secure_erase_trim);
>
> void mmc_rescan(struct work_struct *work)
> {
> diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
> index a811c52..9d9eef5 100644
> --- a/drivers/mmc/core/core.h
> +++ b/drivers/mmc/core/core.h
> @@ -29,6 +29,8 @@ struct mmc_bus_ops {
> void mmc_attach_bus(struct mmc_host *host, const struct mmc_bus_ops *ops);
> void mmc_detach_bus(struct mmc_host *host);
>
> +void mmc_init_erase(struct mmc_card *card);
> +
> void mmc_set_chip_select(struct mmc_host *host, int mode);
> void mmc_set_clock(struct mmc_host *host, unsigned int hz);
> void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode);
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 89f7a25..8eddc97 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -108,13 +108,23 @@ static int mmc_decode_cid(struct mmc_card *card)
> return 0;
> }
>
> +static void mmc_set_erase_size(struct mmc_card *card)
> +{
> + if (card->ext_csd.erase_group_def & 1)
> + card->erase_size = card->ext_csd.hc_erase_size;
> + else
> + card->erase_size = card->csd.erase_size;
> +
> + mmc_init_erase(card);
> +}
> +
> /*
> * Given a 128-bit response, decode to our card CSD structure.
> */
> static int mmc_decode_csd(struct mmc_card *card)
> {
> struct mmc_csd *csd = &card->csd;
> - unsigned int e, m, csd_struct;
> + unsigned int e, m, a, b, csd_struct;
> u32 *resp = card->raw_csd;
>
> /*
> @@ -151,6 +161,11 @@ static int mmc_decode_csd(struct mmc_card *card)
> csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4);
> csd->write_partial = UNSTUFF_BITS(resp, 21, 1);
>
> + a = UNSTUFF_BITS(resp, 42, 5);
> + b = UNSTUFF_BITS(resp, 37, 5);
> + csd->erase_size = (a + 1) * (b + 1);
> + csd->erase_size <<= csd->write_blkbits;
> +
> return 0;
> }
>
> @@ -247,8 +262,30 @@ static int mmc_read_ext_csd(struct mmc_card *card)
> if (sa_shift > 0 && sa_shift <= 0x17)
> card->ext_csd.sa_timeout =
> 1 << ext_csd[EXT_CSD_S_A_TIMEOUT];
> + card->ext_csd.erase_group_def =
> + ext_csd[EXT_CSD_ERASE_GROUP_DEF];
> + card->ext_csd.hc_erase_timeout = 300 *
> + ext_csd[EXT_CSD_ERASE_TIMEOUT_MULT];
> + card->ext_csd.hc_erase_size =
> + ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] << 19;
> + }
> +
> + if (card->ext_csd.rev >= 4) {
> + card->ext_csd.sec_trim_mult =
> + ext_csd[EXT_CSD_SEC_TRIM_MULT];
> + card->ext_csd.sec_erase_mult =
> + ext_csd[EXT_CSD_SEC_ERASE_MULT];
> + card->ext_csd.sec_feature_support =
> + ext_csd[EXT_CSD_SEC_FEATURE_SUPPORT];
> + card->ext_csd.trim_timeout = 300 *
> + ext_csd[EXT_CSD_TRIM_MULT];
> }
>
> + if (ext_csd[EXT_CSD_ERASED_MEM_CONT])
> + card->erased_byte = 0xFF;
> + else
> + card->erased_byte = 0x0;
> +
> out:
> kfree(ext_csd);
>
> @@ -260,6 +297,7 @@ MMC_DEV_ATTR(cid, "%08x%08x%08x%08x\n", card->raw_cid[0], card->raw_cid[1],
> MMC_DEV_ATTR(csd, "%08x%08x%08x%08x\n", card->raw_csd[0], card->raw_csd[1],
> card->raw_csd[2], card->raw_csd[3]);
> MMC_DEV_ATTR(date, "%02d/%04d\n", card->cid.month, card->cid.year);
> +MMC_DEV_ATTR(erase_size, "%u\n", card->erase_size);
> MMC_DEV_ATTR(fwrev, "0x%x\n", card->cid.fwrev);
> MMC_DEV_ATTR(hwrev, "0x%x\n", card->cid.hwrev);
> MMC_DEV_ATTR(manfid, "0x%06x\n", card->cid.manfid);
> @@ -271,6 +309,7 @@ static struct attribute *mmc_std_attrs[] = {
> &dev_attr_cid.attr,
> &dev_attr_csd.attr,
> &dev_attr_date.attr,
> + &dev_attr_erase_size.attr,
> &dev_attr_fwrev.attr,
> &dev_attr_hwrev.attr,
> &dev_attr_manfid.attr,
> @@ -407,6 +446,8 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> err = mmc_read_ext_csd(card);
> if (err)
> goto free_card;
> + /* Erase size depends on CSD and Extended CSD */
> + mmc_set_erase_size(card);
> }
>
> /*
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index 5eac21d..6054f62 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -119,6 +119,13 @@ static int mmc_decode_csd(struct mmc_card *card)
> csd->r2w_factor = UNSTUFF_BITS(resp, 26, 3);
> csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4);
> csd->write_partial = UNSTUFF_BITS(resp, 21, 1);
> +
> + if (UNSTUFF_BITS(resp, 46, 1))
> + csd->erase_size = 512;
> + else {
> + csd->erase_size = UNSTUFF_BITS(resp, 39, 7) + 1;
> + csd->erase_size <<= csd->write_blkbits;
> + }
> break;
> case 1:
> /*
> @@ -147,6 +154,7 @@ static int mmc_decode_csd(struct mmc_card *card)
> csd->r2w_factor = 4; /* Unused */
> csd->write_blkbits = 9;
> csd->write_partial = 0;
> + csd->erase_size = 512;
> break;
> default:
> printk(KERN_ERR "%s: unrecognised CSD structure version %d\n",
> @@ -154,6 +162,8 @@ static int mmc_decode_csd(struct mmc_card *card)
> return -EINVAL;
> }
>
> + card->erase_size = csd->erase_size;
> +
> return 0;
> }
>
> @@ -179,10 +189,68 @@ static int mmc_decode_scr(struct mmc_card *card)
> scr->sda_vsn = UNSTUFF_BITS(resp, 56, 4);
> scr->bus_widths = UNSTUFF_BITS(resp, 48, 4);
>
> + if (UNSTUFF_BITS(resp, 55, 1))
> + card->erased_byte = 0xFF;
> + else
> + card->erased_byte = 0x0;
> +
> return 0;
> }
>
> /*
> + * Fetch and process SD Status register.
> + */
> +static int mmc_read_ssr(struct mmc_card *card)
> +{
> + unsigned int au, es, et, eo;
> + int err, i;
> + u32 *ssr;
> +
> + if (!(card->csd.cmdclass & CCC_APP_SPEC)) {
> + printk(KERN_WARNING "%s: card lacks mandatory SD Status "
> + "function.\n", mmc_hostname(card->host));
> + return 0;
> + }
> +
> + ssr = kmalloc(64, GFP_KERNEL);
> + if (!ssr)
> + return -ENOMEM;
> +
> + err = mmc_app_sd_status(card, ssr);
> + if (err) {
> + printk(KERN_WARNING "%s: problem reading SD Status "
> + "register.\n", mmc_hostname(card->host));
> + err = 0;
> + goto out;
> + }
> +
> + for (i = 0; i < 16; i++)
> + ssr[i] = be32_to_cpu(ssr[i]);
> +
> + /*
> + * UNSTUFF_BITS only works with four u32s so we have to offset the
> + * bitfield positions accordingly.
> + */
> + au = UNSTUFF_BITS(ssr, 428 - 384, 4);
> + if (au > 0 || au <= 9) {
> + card->ssr.au = 1 << (au + 4);
> + es = UNSTUFF_BITS(ssr, 408 - 384, 16);
> + et = UNSTUFF_BITS(ssr, 402 - 384, 6);
> + eo = UNSTUFF_BITS(ssr, 400 - 384, 2);
> + if (es && et) {
> + card->ssr.erase_timeout = (et * 1000) / es;
> + card->ssr.erase_offset = eo * 1000;
> + }
> + } else {
> + printk(KERN_WARNING "%s: SD Status: Invalid Allocation Unit "
> + "size.\n", mmc_hostname(card->host));
> + }
> +out:
> + kfree(ssr);
> + return err;
> +}
> +
> +/*
> * Fetches and decodes switch information
> */
> static int mmc_read_switch(struct mmc_card *card)
> @@ -289,6 +357,7 @@ MMC_DEV_ATTR(csd, "%08x%08x%08x%08x\n", card->raw_csd[0], card->raw_csd[1],
> card->raw_csd[2], card->raw_csd[3]);
> MMC_DEV_ATTR(scr, "%08x%08x\n", card->raw_scr[0], card->raw_scr[1]);
> MMC_DEV_ATTR(date, "%02d/%04d\n", card->cid.month, card->cid.year);
> +MMC_DEV_ATTR(erase_size, "%u\n", card->erase_size);
> MMC_DEV_ATTR(fwrev, "0x%x\n", card->cid.fwrev);
> MMC_DEV_ATTR(hwrev, "0x%x\n", card->cid.hwrev);
> MMC_DEV_ATTR(manfid, "0x%06x\n", card->cid.manfid);
> @@ -302,6 +371,7 @@ static struct attribute *sd_std_attrs[] = {
> &dev_attr_csd.attr,
> &dev_attr_scr.attr,
> &dev_attr_date.attr,
> + &dev_attr_erase_size.attr,
> &dev_attr_fwrev.attr,
> &dev_attr_hwrev.attr,
> &dev_attr_manfid.attr,
> @@ -442,6 +512,16 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
> goto free_card;
>
> /*
> + * Fetch and process SD Status register.
> + */
> + err = mmc_read_ssr(card);
> + if (err)
> + goto free_card;
> +
> + /* Erase init depends on CSD and SSR */
> + mmc_init_erase(card);
> +
> + /*
> * Fetch switch information from card.
> */
> err = mmc_read_switch(card);
> diff --git a/drivers/mmc/core/sd_ops.c b/drivers/mmc/core/sd_ops.c
> index 0d96080..7ca5774 100644
> --- a/drivers/mmc/core/sd_ops.c
> +++ b/drivers/mmc/core/sd_ops.c
> @@ -348,3 +348,51 @@ int mmc_sd_switch(struct mmc_card *card, int mode, int group,
> return 0;
> }
>
> +int mmc_app_sd_status(struct mmc_card *card, void *ssr)
> +{
> + int err;
> + struct mmc_request mrq;
> + struct mmc_command cmd;
> + struct mmc_data data;
> + struct scatterlist sg;
> +
> + BUG_ON(!card);
> + BUG_ON(!card->host);
> + BUG_ON(!ssr);
> +
> + /* NOTE: caller guarantees ssr is heap-allocated */
> +
> + err = mmc_app_cmd(card->host, card);
> + if (err)
> + return err;
> +
> + memset(&mrq, 0, sizeof(struct mmc_request));
> + memset(&cmd, 0, sizeof(struct mmc_command));
> + memset(&data, 0, sizeof(struct mmc_data));
> +
> + mrq.cmd = &cmd;
> + mrq.data = &data;
> +
> + cmd.opcode = SD_APP_SD_STATUS;
> + cmd.arg = 0;
> + cmd.flags = MMC_RSP_SPI_R2 | MMC_RSP_R1 | MMC_CMD_ADTC;
> +
> + data.blksz = 64;
> + data.blocks = 1;
> + data.flags = MMC_DATA_READ;
> + data.sg = &sg;
> + data.sg_len = 1;
> +
> + sg_init_one(&sg, ssr, 64);
> +
> + mmc_set_data_timeout(&data, card);
> +
> + mmc_wait_for_req(card->host, &mrq);
> +
> + if (cmd.error)
> + return cmd.error;
> + if (data.error)
> + return data.error;
> +
> + return 0;
> +}
> diff --git a/drivers/mmc/core/sd_ops.h b/drivers/mmc/core/sd_ops.h
> index 9742d8a..ffc2305 100644
> --- a/drivers/mmc/core/sd_ops.h
> +++ b/drivers/mmc/core/sd_ops.h
> @@ -19,6 +19,7 @@ int mmc_send_relative_addr(struct mmc_host *host, unsigned int *rca);
> int mmc_app_send_scr(struct mmc_card *card, u32 *scr);
> int mmc_sd_switch(struct mmc_card *card, int mode, int group,
> u8 value, u8 *resp);
> +int mmc_app_sd_status(struct mmc_card *card, void *ssr);
>
> #endif
>
> diff --git a/include/linux/Kbuild b/include/linux/Kbuild
> index 2fc8e14..cca6850 100644
> --- a/include/linux/Kbuild
> +++ b/include/linux/Kbuild
> @@ -3,6 +3,7 @@ header-y += can/
> header-y += dvb/
> header-y += hdlc/
> header-y += isdn/
> +header-y += mmc/
> header-y += nfsd/
> header-y += raid/
> header-y += spi/
> diff --git a/include/linux/mmc/Kbuild b/include/linux/mmc/Kbuild
> new file mode 100644
> index 0000000..547136d
> --- /dev/null
> +++ b/include/linux/mmc/Kbuild
> @@ -0,0 +1 @@
> +header-y += mmc_ioctl.h
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index d02d2c6..bbbcc95 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -30,6 +30,7 @@ struct mmc_csd {
> unsigned int tacc_ns;
> unsigned int r2w_factor;
> unsigned int max_dtr;
> + unsigned int erase_size;
> unsigned int read_blkbits;
> unsigned int write_blkbits;
> unsigned int capacity;
> @@ -41,9 +42,16 @@ struct mmc_csd {
>
> struct mmc_ext_csd {
> u8 rev;
> + u8 erase_group_def;
> + u8 sec_feature_support;
> unsigned int sa_timeout; /* Units: 100ns */
> unsigned int hs_max_dtr;
> unsigned int sectors;
> + unsigned int hc_erase_size; /* In bytes */
> + unsigned int hc_erase_timeout; /* In milliseconds */
> + unsigned int sec_trim_mult; /* Secure trim multiplier */
> + unsigned int sec_erase_mult; /* Secure erase multiplier */
> + unsigned int trim_timeout; /* In milliseconds */
> };
>
> struct sd_scr {
> @@ -53,6 +61,12 @@ struct sd_scr {
> #define SD_SCR_BUS_WIDTH_4 (1<<2)
> };
>
> +struct sd_ssr {
> + unsigned int au; /* In sectors */
> + unsigned int erase_timeout; /* In milliseconds */
> + unsigned int erase_offset; /* In milliseconds */
> +};
> +
> struct sd_switch_caps {
> unsigned int hs_max_dtr;
> };
> @@ -101,6 +115,10 @@ struct mmc_card {
> #define MMC_QUIRK_LENIENT_FN0 (1<<0) /* allow SDIO FN0 writes outside of the VS CCCR range */
> #define MMC_QUIRK_BLKSZ_FOR_BYTE_MODE (1<<1) /* use func->cur_blksize */
> /* for byte mode */
> + unsigned int erase_size; /* erase size in bytes */
> + unsigned int erase_shift; /* if erase unit is power 2 */
> + unsigned int max_erase; /* in sectors */
> + u8 erased_byte; /* value of erased bytes */
>
> u32 raw_cid[4]; /* raw card CID */
> u32 raw_csd[4]; /* raw card CSD */
> @@ -109,6 +127,7 @@ struct mmc_card {
> struct mmc_csd csd; /* card specific */
> struct mmc_ext_csd ext_csd; /* mmc v4 extended card specific */
> struct sd_scr scr; /* extra SD information */
> + struct sd_ssr ssr; /* yet more SD information */
> struct sd_switch_caps sw_caps; /* switch (CMD6) caps */
>
> unsigned int sdio_funcs; /* number of SDIO functions */
> diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
> index e4898e9..af3dded 100644
> --- a/include/linux/mmc/core.h
> +++ b/include/linux/mmc/core.h
> @@ -92,6 +92,8 @@ struct mmc_command {
> * actively failing requests
> */
>
> + unsigned int erase_timeout; /* in milliseconds */
> +
> struct mmc_data *data; /* data segment associated with cmd */
> struct mmc_request *mrq; /* associated request */
> };
> @@ -134,6 +136,21 @@ extern int mmc_wait_for_cmd(struct mmc_host *, struct mmc_command *, int);
> extern int mmc_wait_for_app_cmd(struct mmc_host *, struct mmc_card *,
> struct mmc_command *, int);
>
> +#define MMC_ERASE_ARG 0x00000000
> +#define MMC_SECURE_ERASE_ARG 0x80000000
> +#define MMC_TRIM_ARG 0x00000001
> +#define MMC_SECURE_TRIM1_ARG 0x80000001
> +#define MMC_SECURE_TRIM2_ARG 0x80008000
> +
> +#define MMC_SECURE_ARGS 0x80000000
> +#define MMC_TRIM_ARGS 0x00008001
> +
> +extern int mmc_erase(struct mmc_card *card, unsigned int from, unsigned int nr,
> + unsigned int arg);
> +extern int mmc_can_erase(struct mmc_card *card);
> +extern int mmc_can_trim(struct mmc_card *card);
> +extern int mmc_can_secure_erase_trim(struct mmc_card *card);
> +
> extern void mmc_set_data_timeout(struct mmc_data *, const struct mmc_card *);
> extern unsigned int mmc_align_data_size(struct mmc_card *, unsigned int);
>
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 43eaf5c..270f281 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -152,6 +152,7 @@ struct mmc_host {
> #define MMC_CAP_DISABLE (1 << 7) /* Can the host be disabled */
> #define MMC_CAP_NONREMOVABLE (1 << 8) /* Nonremovable e.g. eMMC */
> #define MMC_CAP_WAIT_WHILE_BUSY (1 << 9) /* Waits while card is busy */
> +#define MMC_CAP_ERASE (1 << 10) /* Allow erase/trim commands */
>
> mmc_pm_flag_t pm_caps; /* supported pm features */
>
> diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
> index 8a49cbf..82cdf8b 100644
> --- a/include/linux/mmc/mmc.h
> +++ b/include/linux/mmc/mmc.h
> @@ -251,12 +251,20 @@ struct _mmc_csd {
> * EXT_CSD fields
> */
>
> -#define EXT_CSD_BUS_WIDTH 183 /* R/W */
> -#define EXT_CSD_HS_TIMING 185 /* R/W */
> -#define EXT_CSD_CARD_TYPE 196 /* RO */
> -#define EXT_CSD_REV 192 /* RO */
> -#define EXT_CSD_SEC_CNT 212 /* RO, 4 bytes */
> -#define EXT_CSD_S_A_TIMEOUT 217
> +#define EXT_CSD_ERASE_GROUP_DEF 175 /* R/W */
> +#define EXT_CSD_ERASED_MEM_CONT 181 /* RO */
> +#define EXT_CSD_BUS_WIDTH 183 /* R/W */
> +#define EXT_CSD_HS_TIMING 185 /* R/W */
> +#define EXT_CSD_CARD_TYPE 196 /* RO */
> +#define EXT_CSD_REV 192 /* RO */
> +#define EXT_CSD_SEC_CNT 212 /* RO, 4 bytes */
> +#define EXT_CSD_S_A_TIMEOUT 217 /* RO */
> +#define EXT_CSD_ERASE_TIMEOUT_MULT 223 /* RO */
> +#define EXT_CSD_HC_ERASE_GRP_SIZE 224 /* RO */
> +#define EXT_CSD_SEC_TRIM_MULT 229 /* RO */
> +#define EXT_CSD_SEC_ERASE_MULT 230 /* RO */
> +#define EXT_CSD_SEC_FEATURE_SUPPORT 231 /* RO */
> +#define EXT_CSD_TRIM_MULT 232 /* RO */
>
> /*
> * EXT_CSD field definitions
> @@ -274,6 +282,10 @@ struct _mmc_csd {
> #define EXT_CSD_BUS_WIDTH_4 1 /* Card is in 4 bit mode */
> #define EXT_CSD_BUS_WIDTH_8 2 /* Card is in 8 bit mode */
>
> +#define EXT_CSD_SEC_ER_EN BIT(0)
> +#define EXT_CSD_SEC_BD_BLK_EN BIT(2)
> +#define EXT_CSD_SEC_GB_CL_EN BIT(4)
> +
> /*
> * MMC_SWITCH access modes
> */
> diff --git a/include/linux/mmc/mmc_ioctl.h b/include/linux/mmc/mmc_ioctl.h
> new file mode 100644
> index 0000000..f9737dd
> --- /dev/null
> +++ b/include/linux/mmc/mmc_ioctl.h
> @@ -0,0 +1,63 @@
> +/*
> + * linux/include/linux/mmc/mmc_ioctl.h
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#ifndef LINUX_MMC_MMC_IOCTL_H
> +#define LINUX_MMC_MMC_IOCTL_H
> +
> +#include <linux/types.h>
> +#include <linux/ioctl.h>
> +
> +/* Same as MMC block device major number */
> +#define MMC_IOCTL_CODE 0xB3
> +
> +#define MMCERASEINFO _IOR(MMC_IOCTL_CODE, 1, struct mmc_blk_erase_info)
> +#define MMCERASE _IOW(MMC_IOCTL_CODE, 2, struct mmc_blk_erase_args)
> +
> +/* Erase flags */
> +#define MMC_ERASE_FLAG 0x01
> +#define MMC_SECURE_ERASE_FLAG 0x02
> +#define MMC_TRIM_FLAG 0x04
> +#define MMC_SECURE_TRIM1_FLAG 0x08
> +#define MMC_SECURE_TRIM2_FLAG 0x10
> +
> +/**
> + * struct mmc_blk_erase_info - erase information.
> + * @erase_size: minimum unit of erasure in bytes
> + * @flags: flags indicating which kinds of erase are permitted
> + * @erased_byte: value of bytes that have been erased (0x00 or 0xFF)
> + * @reserved: reserved
> + */
> +struct mmc_blk_erase_info {
> + __u32 erase_size;
> + __u32 flags;
> + __u8 erased_byte;
> + __u8 reserved[23];
> +} __attribute__ ((packed));
> +
> +/**
> + * struct mmc_blk_erase_args - erase SD or MMC sectors.
> + * @from: start sector number
> + * @nr: number of sectors to erase
> + * @flag: flag indicating which kind of erase to do
> + * @reserved: reserved
> + *
> + * @flag must be one of the flags above. For %MMC_ERASE_FLAG and
> + * %MMC_SECURE_ERASE_FLAG, @from and @nr must be multiples of the erase_size
> + * returned by the %MMCERASEINFO ioctl. %MMC_ERASE_FLAG may be used with
> + * MMC or SD cards, whereas the other flags are only valid for MMCv4.4 or
> + * later.
> + */
> +struct mmc_blk_erase_args {
> + __u32 from;
> + __u32 nr;
> + __u32 flag;
> + __u8 reserved[20];
> +} __attribute__ ((packed));
> +
> +#endif /* LINUX_MMC_MMC_IOCTL_H */
> diff --git a/include/linux/mmc/sd.h b/include/linux/mmc/sd.h
> index f310062..3fd85e0 100644
> --- a/include/linux/mmc/sd.h
> +++ b/include/linux/mmc/sd.h
> @@ -21,8 +21,13 @@
> /* class 10 */
> #define SD_SWITCH 6 /* adtc [31:0] See below R1 */
>
> + /* class 5 */
> +#define SD_ERASE_WR_BLK_START 32 /* ac [31:0] data addr R1 */
> +#define SD_ERASE_WR_BLK_END 33 /* ac [31:0] data addr R1 */
> +
> /* Application commands */
> #define SD_APP_SET_BUS_WIDTH 6 /* ac [1:0] bus width R1 */
> +#define SD_APP_SD_STATUS 13 /* adtc R1 */
> #define SD_APP_SEND_NUM_WR_BLKS 22 /* adtc R1 */
> #define SD_APP_OP_COND 41 /* bcr [31:0] OCR R3 */
> #define SD_APP_SEND_SCR 51 /* adtc R1 */
> --
> 1.6.3.3
>
> --
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From: Christoph Hellwig on 31 May 2010 04:50

---

On Mon, May 31, 2010 at 11:45:37AM +0300, Adrian Hunter wrote:
> Sorry for the slow reply, I have been away.
>
> Connecting erase to discard was rejected for performance reasons in 2008.
> Refer:
>
> http://thread.gmane.org/gmane.linux.file-systems/25378/focus=25606

The discard implementation changed a lot since those days. Discard
requests now have their own request size limitation which is separate
form that for normal requests, and we also store the alignment
requirement for them separately.

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From: Adrian Hunter on 31 May 2010 04:50

---

Christoph Hellwig wrote:
> On Fri, May 21, 2010 at 04:47:40PM +0300, Adrian Hunter wrote:
>>> From f3baf566eb33a22bf12a48e4cdc7c99611bde934 Mon Sep 17 00:00:00 2001
>> From: Adrian Hunter <adrian.hunter(a)nokia.com>
>> Date: Wed, 5 May 2010 14:07:55 +0300
>> Subject: [PATCH] mmc: add an ioctl for erasing
>>
>> As SD and MMC cards have a NAND core, they can support an erase
>> operation that is typically 10x to 100x faster than writing.
>>
>> In addition, eMMCv4.4 also offers:
>> o Secure Erase
>> o Trim
>> o Secure Trim
>>
>> The "secure" variants also ensure that any copies of the data
>> (for example remnants of garbage collection) are also erased.
>>
>> "Trim" is the same as "erase" except that individual sectors
>> can be erased instead of whole Erase Groups.
>>
>> The Erase Operation and its variants are not supported by
>> default and drivers must set MMC_CAP_ERASE. This is because
>> the operation can take a long time and drivers that rely on
>> polling the status may perform very badly. Also drivers
>> may need changes to support the very long erase timeouts.
>
> Please don't add new device specific ioctls. Just implement the
> block layer discard operation to make the discard ioctl work on MMC
> device. We can talk about adding a secure erase variant of it then.

Sorry for the slow reply, I have been away.

Connecting erase to discard was rejected for performance reasons in 2008.
Refer:

http://thread.gmane.org/gmane.linux.file-systems/25378/focus=25606


We may want to connect MMC trim to discard, but I suspect it might have the
same performance problems.

My requirement is to expose erase and secure erase to userspace. The discard
operation is not appropriate and the discard ioctl is too limited.

I could shift the ioctls to the block layer?
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From: Adrian Hunter on 31 May 2010 05:20

---

Christoph Hellwig wrote:
> On Mon, May 31, 2010 at 11:45:37AM +0300, Adrian Hunter wrote:
>> Sorry for the slow reply, I have been away.
>>
>> Connecting erase to discard was rejected for performance reasons in 2008.
>> Refer:
>>
>> http://thread.gmane.org/gmane.linux.file-systems/25378/focus=25606
>
> The discard implementation changed a lot since those days. Discard
> requests now have their own request size limitation which is separate
> form that for normal requests, and we also store the alignment
> requirement for them separately.
>


I tested extensively at that time with all changes necessary to allow
discards to produce MMC erases that work with maximum efficacy. There was
no performance benefit and operations like file deletion were much slower.

If connecting discard to MMC erase does not always improve performance, then
many people will have to change their mount options to include nodiscard.
Alternatively, if the connection is an optional configuration, then the
ioctl won't work all the time.

The erase ioctl needs to be separate from discard, which means it can be
made to support secure erase also.
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