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clockevents/drivers/i8253: Add support for PIT shutdown quirk 

Add support for platforms where pit_shutdown() doesn't work because of a
quirk in the PIT emulation. On these platforms setting the counter register
to zero causes the PIT to start running again, negating the shutdown.

Provide a global variable that controls whether the counter register is
zero'ed, which platform specific code can override.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>
Cc: "daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>
Cc: "virtualization@lists.linux-foundation.org" <virtualization@lists.linux-foundation.org>
Cc: "jgross@suse.com" <jgross@suse.com>
Cc: "akataria@vmware.com" <akataria@vmware.com>
Cc: "olaf@aepfle.de" <olaf@aepfle.de>
Cc: "apw@canonical.com" <apw@canonical.com>
Cc: vkuznets <vkuznets@redhat.com>
Cc: "jasowang@redhat.com" <jasowang@redhat.com>
Cc: "marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>
Cc: KY Srinivasan <kys@microsoft.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1541303219-11142-2-git-send-email-mikelley@microsoft.com
This commit is contained in:
Michael Kelley 2018-11-04 03:48:54 +00:00 committed by Thomas Gleixner
parent 71e5602817
commit 35b69a420b
2 changed files with 13 additions and 2 deletions
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14
drivers/clocksource/i8253.c
View File

@ -20,6 +20,13 @@
DEFINE_RAW_SPINLOCK(i8253_lock);
EXPORT_SYMBOL(i8253_lock);
/*
* Handle PIT quirk in pit_shutdown() where zeroing the counter register
* restarts the PIT, negating the shutdown. On platforms with the quirk,
* platform specific code can set this to false.
*/
bool i8253_clear_counter_on_shutdown __ro_after_init = true;
#ifdef CONFIG_CLKSRC_I8253
/*
* Since the PIT overflows every tick, its not very useful
@ -109,8 +116,11 @@ static int pit_shutdown(struct clock_event_device *evt)
raw_spin_lock(&i8253_lock);
outb_p(0x30, PIT_MODE);
outb_p(0, PIT_CH0);
outb_p(0, PIT_CH0);
if (i8253_clear_counter_on_shutdown) {
outb_p(0, PIT_CH0);
outb_p(0, PIT_CH0);
}
raw_spin_unlock(&i8253_lock);
return 0;

1
include/linux/i8253.h
View File

@ -21,6 +21,7 @@
#define PIT_LATCH ((PIT_TICK_RATE + HZ/2) / HZ)
extern raw_spinlock_t i8253_lock;
extern bool i8253_clear_counter_on_shutdown;
extern struct clock_event_device i8253_clockevent;
extern void clockevent_i8253_init(bool oneshot);