projects / thirdparty / kernel / stable-queue.git / blame
| Commit | Line | Data |
|---|---|---|
| 9f934a63 GKH |
1 | From 96e9694df446d1154ec2f4fdba8908588b9cba38 Mon Sep 17 00:00:00 2001 |
| 2 | From: Clemens Ladisch <clemens@ladisch.de> | |
| 3 | Date: Tue, 26 Oct 2010 14:22:13 -0700 | |
| 4 | Subject: hpet: fix unwanted interrupt due to stale irq status bit | |
| 5 | ||
| 6 | From: Clemens Ladisch <clemens@ladisch.de> | |
| 7 | ||
| 8 | commit 96e9694df446d1154ec2f4fdba8908588b9cba38 upstream. | |
| 9 | ||
| 10 | Jaswinder Singh Rajput wrote: | |
| 11 | > By executing Documentation/timers/hpet_example.c | |
| 12 | > | |
| 13 | > for polling, I requested for 3 iterations but it seems iteration work | |
| 14 | > for only 2 as first expired time is always very small. | |
| 15 | > | |
| 16 | > # ./hpet_example poll /dev/hpet 10 3 | |
| 17 | > -hpet: executing poll | |
| 18 | > hpet_poll: info.hi_flags 0x0 | |
| 19 | > hpet_poll: expired time = 0x13 | |
| 20 | > hpet_poll: revents = 0x1 | |
| 21 | > hpet_poll: data 0x1 | |
| 22 | > hpet_poll: expired time = 0x1868c | |
| 23 | > hpet_poll: revents = 0x1 | |
| 24 | > hpet_poll: data 0x1 | |
| 25 | > hpet_poll: expired time = 0x18645 | |
| 26 | > hpet_poll: revents = 0x1 | |
| 27 | > hpet_poll: data 0x1 | |
| 28 | ||
| 29 | Clearing the HPET interrupt enable bit disables interrupt generation | |
| 30 | but does not disable the timer, so the interrupt status bit will still | |
| 31 | be set when the timer elapses. If another interrupt arrives before | |
| 32 | the timer has been correctly programmed (due to some other device on | |
| 33 | the same interrupt line, or CONFIG_DEBUG_SHIRQ), this results in an | |
| 34 | extra unwanted interrupt event because the status bit is likely to be | |
| 35 | set from comparator matches that happened before the device was opened. | |
| 36 | ||
| 37 | Therefore, we have to ensure that the interrupt status bit is and | |
| 38 | stays cleared until we actually program the timer. | |
| 39 | ||
| 40 | Signed-off-by: Clemens Ladisch <clemens@ladisch.de> | |
| 41 | Reported-by: Jaswinder Singh Rajput <jaswinderlinux@gmail.com> | |
| 42 | Cc: Ingo Molnar <mingo@elte.hu> | |
| 43 | Cc: Thomas Gleixner <tglx@linutronix.de> | |
| 44 | Cc: john stultz <johnstul@us.ibm.com> | |
| 45 | Cc: Bob Picco <bpicco@redhat.com> | |
| 46 | Signed-off-by: Andrew Morton <akpm@linux-foundation.org> | |
| 47 | Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> | |
| 48 | Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> | |
| 49 | ||
| 50 | --- | |
| 51 | drivers/char/hpet.c | 15 +++++++++++++++ | |
| 52 | 1 file changed, 15 insertions(+) | |
| 53 | ||
| 54 | --- a/drivers/char/hpet.c | |
| 55 | +++ b/drivers/char/hpet.c | |
| 56 | @@ -479,6 +479,21 @@ static int hpet_ioctl_ieon(struct hpet_d | |
| 57 | if (irq) { | |
| 58 | unsigned long irq_flags; | |
| 59 | ||
| 60 | + if (devp->hd_flags & HPET_SHARED_IRQ) { | |
| 61 | + /* | |
| 62 | + * To prevent the interrupt handler from seeing an | |
| 63 | + * unwanted interrupt status bit, program the timer | |
| 64 | + * so that it will not fire in the near future ... | |
| 65 | + */ | |
| 66 | + writel(readl(&timer->hpet_config) & ~Tn_TYPE_CNF_MASK, | |
| 67 | + &timer->hpet_config); | |
| 68 | + write_counter(read_counter(&hpet->hpet_mc), | |
| 69 | + &timer->hpet_compare); | |
| 70 | + /* ... and clear any left-over status. */ | |
| 71 | + isr = 1 << (devp - devp->hd_hpets->hp_dev); | |
| 72 | + writel(isr, &hpet->hpet_isr); | |
| 73 | + } | |
| 74 | + | |
| 75 | sprintf(devp->hd_name, "hpet%d", (int)(devp - hpetp->hp_dev)); | |
| 76 | irq_flags = devp->hd_flags & HPET_SHARED_IRQ | |
| 77 | ? IRQF_SHARED : IRQF_DISABLED; |