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From: Ben Hutchings on 23 Jul 2010 10:00
commit 2ca1af9aa3285c6a5f103ed31ad09f7399fc65d7 "PCI: MSI: Remove
unsafe and unnecessary hardware access" changed read_msi_msg_desc() to
return the last MSI message written instead of reading it from the
device, since it may be called while the device is in a reduced
power state.

However, the pSeries platform code really does need to read messages
from the device, since they are initially written by firmware.
Therefore:
- Restore the previous behaviour of read_msi_msg_desc()
- Add new functions get_cached_msi_msg{,_desc}() which return the
last MSI message written
- Use the new functions where appropriate

Signed-off-by: Ben Hutchings <bhutchings(a)solarflare.com>
---
Compile-tested only.

Ben.

arch/ia64/kernel/msi_ia64.c | 2 +-
arch/ia64/sn/kernel/msi_sn.c | 2 +-
arch/x86/kernel/apic/io_apic.c | 2 +-
drivers/pci/msi.c | 47 +++++++++++++++++++++++++++++++++++----
include/linux/msi.h | 2 +
5 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/kernel/msi_ia64.c b/arch/ia64/kernel/msi_ia64.c
index 6c89228..4a746ea 100644
--- a/arch/ia64/kernel/msi_ia64.c
+++ b/arch/ia64/kernel/msi_ia64.c
@@ -25,7 +25,7 @@ static int ia64_set_msi_irq_affinity(unsigned int irq,
if (irq_prepare_move(irq, cpu))
return -1;

- read_msi_msg(irq, &msg);
+ get_cached_msi_msg(irq, &msg);

addr = msg.address_lo;
addr &= MSI_ADDR_DEST_ID_MASK;
diff --git a/arch/ia64/sn/kernel/msi_sn.c b/arch/ia64/sn/kernel/msi_sn.c
index ebfdd6a..0c72dd4 100644
--- a/arch/ia64/sn/kernel/msi_sn.c
+++ b/arch/ia64/sn/kernel/msi_sn.c
@@ -175,7 +175,7 @@ static int sn_set_msi_irq_affinity(unsigned int irq,
* Release XIO resources for the old MSI PCI address
*/

- read_msi_msg(irq, &msg);
+ get_cached_msi_msg(irq, &msg);
sn_pdev = (struct pcidev_info *)sn_irq_info->irq_pciioinfo;
pdev = sn_pdev->pdi_linux_pcidev;
provider = SN_PCIDEV_BUSPROVIDER(pdev);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index e41ed24..4dc0084 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3397,7 +3397,7 @@ static int set_msi_irq_affinity(unsigned int irq, const struct cpumask *mask)

cfg = desc->chip_data;

- read_msi_msg_desc(desc, &msg);
+ get_cached_msi_msg_desc(desc, &msg);

msg.data &= ~MSI_DATA_VECTOR_MASK;
msg.data |= MSI_DATA_VECTOR(cfg->vector);
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 4c14f31..69b7be3 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -197,9 +197,46 @@ void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
{
struct msi_desc *entry = get_irq_desc_msi(desc);

- /* We do not touch the hardware (which may not even be
- * accessible at the moment) but return the last message
- * written. Assert that this is valid, assuming that
+ BUG_ON(entry->dev->current_state != PCI_D0);
+
+ if (entry->msi_attrib.is_msix) {
+ void __iomem *base = entry->mask_base +
+ entry->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE;
+
+ msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR);
+ msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR);
+ msg->data = readl(base + PCI_MSIX_ENTRY_DATA);
+ } else {
+ struct pci_dev *dev = entry->dev;
+ int pos = entry->msi_attrib.pos;
+ u16 data;
+
+ pci_read_config_dword(dev, msi_lower_address_reg(pos),
+ &msg->address_lo);
+ if (entry->msi_attrib.is_64) {
+ pci_read_config_dword(dev, msi_upper_address_reg(pos),
+ &msg->address_hi);
+ pci_read_config_word(dev, msi_data_reg(pos, 1), &data);
+ } else {
+ msg->address_hi = 0;
+ pci_read_config_word(dev, msi_data_reg(pos, 0), &data);
+ }
+ msg->data = data;
+ }
+}
+
+void read_msi_msg(unsigned int irq, struct msi_msg *msg)
+{
+ struct irq_desc *desc = irq_to_desc(irq);
+
+ read_msi_msg_desc(desc, msg);
+}
+
+void get_cached_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
+{
+ struct msi_desc *entry = get_irq_desc_msi(desc);
+
+ /* Assert that the cache is valid, assuming that
* valid messages are not all-zeroes. */
BUG_ON(!(entry->msg.address_hi | entry->msg.address_lo |
entry->msg.data));
@@ -207,11 +244,11 @@ void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
*msg = entry->msg;
}

-void read_msi_msg(unsigned int irq, struct msi_msg *msg)
+void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg)
{
struct irq_desc *desc = irq_to_desc(irq);

- read_msi_msg_desc(desc, msg);
+ get_cached_msi_msg_desc(desc, msg);
}

void write_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg)
diff --git a/include/linux/msi.h b/include/linux/msi.h
index 6991ab5..91b05c1 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -14,8 +14,10 @@ struct irq_desc;
extern void mask_msi_irq(unsigned int irq);
extern void unmask_msi_irq(unsigned int irq);
extern void read_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg);
+extern void get_cached_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg);
extern void write_msi_msg_desc(struct irq_desc *desc, struct msi_msg *msg);
extern void read_msi_msg(unsigned int irq, struct msi_msg *msg);
+extern void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg);
extern void write_msi_msg(unsigned int irq, struct msi_msg *msg);

struct msi_desc {
--
1.6.2.5

--
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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Prev: kswapd continuously active when doing IO
Next: cfq-iosched: IOPS mode for group scheduling and new group_idle tunable