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Commit ebbc6fce authored by Michael Kelley's avatar Michael Kelley Committed by Greg Kroah-Hartman
Browse files

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



commit 35b69a420bfb56b7b74cb635ea903db05e357bec upstream.

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: default avatarMichael Kelley <mikelley@microsoft.com>
Signed-off-by: default avatarThomas 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


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f2589f9a

drivers/clocksource/i8253.c

+12 −2
Original line number Diff line number Diff line
@@ -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);



	if (i8253_clear_counter_on_shutdown) {

		outb_p(0, PIT_CH0);

		outb_p(0, PIT_CH0);

	}



	raw_spin_unlock(&i8253_lock);

	return 0;

include/linux/i8253.h

+1 −0
Original line number Diff line number Diff line
@@ -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);