This is a note to let you know that I've just added the patch titled
clockevents/drivers/i8253: Add support for PIT shutdown quirk
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
clockevents-drivers-i8253-add-support-for-pit-shutdown-quirk.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 35b69a420bfb56b7b74cb635ea903db05e357bec Mon Sep 17 00:00:00 2001
From: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Date: Sun, 4 Nov 2018 03:48:54 +0000
Subject: clockevents/drivers/i8253: Add support for PIT shutdown quirk
From: Michael Kelley <mikelley@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "gregkh@xxxxxxxxxxxxxxxxxxx" <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "devel@xxxxxxxxxxxxxxxxxxxxxx" <devel@xxxxxxxxxxxxxxxxxxxxxx>
Cc: "daniel.lezcano@xxxxxxxxxx" <daniel.lezcano@xxxxxxxxxx>
Cc: "virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx" <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: "jgross@xxxxxxxx" <jgross@xxxxxxxx>
Cc: "akataria@xxxxxxxxxx" <akataria@xxxxxxxxxx>
Cc: "olaf@xxxxxxxxx" <olaf@xxxxxxxxx>
Cc: "apw@xxxxxxxxxxxxx" <apw@xxxxxxxxxxxxx>
Cc: vkuznets <vkuznets@xxxxxxxxxx>
Cc: "jasowang@xxxxxxxxxx" <jasowang@xxxxxxxxxx>
Cc: "marcelo.cerri@xxxxxxxxxxxxx" <marcelo.cerri@xxxxxxxxxxxxx>
Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/1541303219-11142-2-git-send-email-mikelley@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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 __ro_after_init = 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);
Patches currently in stable-queue which might be from mikelley@xxxxxxxxxxxxx are
queue-4.4/clockevents-drivers-i8253-add-support-for-pit-shutdown-quirk.patch
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