Prev: [PATCH] PCI quirks: RS780/RS880: work around missing MSI initialization
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From: Clemens Ladisch on 22 Mar 2010 05:10
Not every HPET implementation gets the index of the last timer correct;
if this field is erroneously set to the timer count, the kernel will
allocate one additional timer that does not actually exist.

To work around this, create a helper function to read the number of
timers and to check that the last timer actually exists.

Signed-off-by: Clemens Ladisch <clemens(a)ladisch.de>
---
arch/x86/kernel/hpet.c | 39 ++++++++++++++++++++++++++-------------
drivers/char/hpet.c | 2 +-
2 files changed, 27 insertions(+), 14 deletions(-)

(resent with correct @google address)

--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -162,6 +162,28 @@
_hpet_print_config(__FUNCTION__, __LINE__); \
} while (0)

+#if defined(CONFIG_HPET) || defined(CONFIG_HPET_EMULATE_RTC) || \
+ defined(CONFIG_PCI_MSI)
+static unsigned int hpet_get_num_timers(void)
+{
+ u32 id, number;
+
+ id = hpet_readl(HPET_ID);
+ number = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT) + 1;
+
+ /*
+ * The number field should contain the index of the last timer, not the
+ * count of timers. For hardware that gets this wrong, check that the
+ * last timer actually exists by testing if any interrupt routing bits
+ * are set; unimplemented registers read 0 on SB710.
+ */
+ if (number > 2 && hpet_readl(HPET_Tn_CFG(number - 1) + 4) == 0)
+ number--;
+
+ return number;
+}
+#endif
+
/*
* When the hpet driver (/dev/hpet) is enabled, we need to reserve
* timer 0 and timer 1 in case of RTC emulation.
@@ -177,7 +199,7 @@ static void hpet_reserve_platform_timers
unsigned int nrtimers, i;
struct hpet_data hd;

- nrtimers = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT) + 1;
+ nrtimers = hpet_get_num_timers();

memset(&hd, 0, sizeof(hd));
hd.hd_phys_address = hpet_address;
@@ -593,7 +615,6 @@ static void init_one_hpet_msi_clockevent

static void hpet_msi_capability_lookup(unsigned int start_timer)
{
- unsigned int id;
unsigned int num_timers;
unsigned int num_timers_used = 0;
int i;
@@ -603,10 +624,8 @@ static void hpet_msi_capability_lookup(u

if (boot_cpu_has(X86_FEATURE_ARAT))
return;
- id = hpet_readl(HPET_ID);

- num_timers = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT);
- num_timers++; /* Value read out starts from 0 */
+ num_timers = hpet_get_num_timers();
hpet_print_config();

hpet_devs = kzalloc(sizeof(struct hpet_dev) * num_timers, GFP_KERNEL);
@@ -832,7 +851,6 @@ static int hpet_clocksource_register(voi
*/
int __init hpet_enable(void)
{
- unsigned int id;
int i;

if (!is_hpet_capable())
@@ -870,11 +888,6 @@ int __init hpet_enable(void)
if (hpet_period < HPET_MIN_PERIOD || hpet_period > HPET_MAX_PERIOD)
goto out_nohpet;

- /*
- * Read the HPET ID register to retrieve the IRQ routing
- * information and the number of channels
- */
- id = hpet_readl(HPET_ID);
hpet_print_config();

#ifdef CONFIG_HPET_EMULATE_RTC
@@ -882,14 +895,14 @@ int __init hpet_enable(void)
* The legacy routing mode needs at least two channels, tick timer
* and the rtc emulation channel.
*/
- if (!(id & HPET_ID_NUMBER))
+ if (hpet_get_num_timers() < 2)
goto out_nohpet;
#endif

if (hpet_clocksource_register())
goto out_nohpet;

- if (id & HPET_ID_LEGSUP) {
+ if (hpet_readl(HPET_ID) & HPET_ID_LEGSUP) {
hpet_legacy_clockevent_register();
return 1;
}
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -857,7 +857,7 @@ int hpet_alloc(struct hpet_data *hdp)

ntimer = ((cap & HPET_NUM_TIM_CAP_MASK) >> HPET_NUM_TIM_CAP_SHIFT) + 1;

- if (hpetp->hp_ntimer != ntimer) {
+ if (hpetp->hp_ntimer > ntimer) {
printk(KERN_WARNING "hpet: number irqs doesn't agree"
" with number of timers\n");
kfree(hpetp);
--
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Prev: [PATCH] PCI quirks: RS780/RS880: work around missing MSI initialization
Next: Hwmon: f71882fg: use strict_stro(l|ul) instead of simple_strto$1