4.4-stable review patch. If anyone has any objections, please let me know.
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From: Michael Kelley mikelley@microsoft.com
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: 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@microso... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/clocksource/i8253.c | 14 ++++++++++++-- include/linux/i8253.h | 1 + 2 files changed, 13 insertions(+), 2 deletions(-)
--- a/drivers/clocksource/i8253.c +++ b/drivers/clocksource/i8253.c @@ -19,6 +19,13 @@ 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 = true; + #ifdef CONFIG_CLKSRC_I8253 /* * Since the PIT overflows every tick, its not very useful @@ -108,8 +115,11 @@ static int pit_shutdown(struct clock_eve 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; --- a/include/linux/i8253.h +++ b/include/linux/i8253.h @@ -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);