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Message-ID: <tip-35b69a420bfb56b7b74cb635ea903db05e357bec@git.kernel.org>
Date: Sun, 4 Nov 2018 02:09:55 -0800
From: tip-bot for Michael Kelley <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: marcelo.cerri@...onical.com, mikelley@...rosoft.com,
devel@...uxdriverproject.org, olaf@...fle.de, jgross@...e.com,
jasowang@...hat.com, mingo@...nel.org, apw@...onical.com,
tglx@...utronix.de, daniel.lezcano@...aro.org, hpa@...or.com,
vkuznets@...hat.com, gregkh@...uxfoundation.org,
akataria@...are.com, kys@...rosoft.com,
virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org
Subject: [tip:x86/urgent] clockevents/drivers/i8253: Add support for PIT
shutdown quirk
Commit-ID: 35b69a420bfb56b7b74cb635ea903db05e357bec
Gitweb: https://git.kernel.org/tip/35b69a420bfb56b7b74cb635ea903db05e357bec
Author: Michael Kelley <mikelley@...rosoft.com>
AuthorDate: Sun, 4 Nov 2018 03:48:54 +0000
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sun, 4 Nov 2018 11:04:46 +0100
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@...rosoft.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc: "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>
Cc: "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>
Cc: "virtualization@...ts.linux-foundation.org" <virtualization@...ts.linux-foundation.org>
Cc: "jgross@...e.com" <jgross@...e.com>
Cc: "akataria@...are.com" <akataria@...are.com>
Cc: "olaf@...fle.de" <olaf@...fle.de>
Cc: "apw@...onical.com" <apw@...onical.com>
Cc: vkuznets <vkuznets@...hat.com>
Cc: "jasowang@...hat.com" <jasowang@...hat.com>
Cc: "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>
Cc: KY Srinivasan <kys@...rosoft.com>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/1541303219-11142-2-git-send-email-mikelley@microsoft.com
---
drivers/clocksource/i8253.c | 14 ++++++++++++--
include/linux/i8253.h | 1 +
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/clocksource/i8253.c b/drivers/clocksource/i8253.c
index 9c38895542f4..d4350bb10b83 100644
--- a/drivers/clocksource/i8253.c
+++ b/drivers/clocksource/i8253.c
@@ -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;
diff --git a/include/linux/i8253.h b/include/linux/i8253.h
index e6bb36a97519..8336b2f6f834 100644
--- 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);
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