From: Michael Kelley <mikelley@microsoft.com>
To: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
"jgross@suse.com" <jgross@suse.com>,
"akataria@vmware.com" <akataria@vmware.com>,
"olaf@aepfle.de" <olaf@aepfle.de>,
"apw@canonical.com" <apw@canonical.com>,
vkuznets <vkuznets@redhat.com>,
"jasowang@redhat.com" <jasowang@redhat.com>,
"marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>,
KY Srinivasan <kys@microsoft.com>
Cc: Michael Kelley <mikelley@microsoft.com>
Subject: [PATCH v2 1/2] i8253: Add support for PIT shutdown quirk
Date: Sun, 4 Nov 2018 03:48:54 +0000 [thread overview]
Message-ID: <1541303219-11142-2-git-send-email-mikelley@microsoft.com> (raw)
In-Reply-To: <1541303219-11142-1-git-send-email-mikelley@microsoft.com>
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>
---
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 9c38895..2a4202a 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 __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) {
+ 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 e6bb36a..31c4be5 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;
extern struct clock_event_device i8253_clockevent;
extern void clockevent_i8253_init(bool oneshot);
--
1.8.3.1
next prev parent reply other threads:[~2018-11-04 3:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-04 3:48 [PATCH v2 0/2] i8253: Fix PIT shutdown quirk on Hyper-V Michael Kelley
2018-11-04 3:48 ` Michael Kelley [this message]
2018-11-04 10:09 ` [tip:x86/urgent] clockevents/drivers/i8253: Add support for PIT shutdown quirk tip-bot for Michael Kelley
2018-11-04 3:48 ` [PATCH v2 2/2] x86/hyper-v: Enable " Michael Kelley
2018-11-04 10:10 ` [tip:x86/urgent] " tip-bot for Michael Kelley
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