linux-kernel - [tip:timers/urgent] clocksource/drivers/sun5i: Fix cpufreq interaction with sched

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Date:	Thu, 26 Mar 2015 06:46:48 -0700
From:	tip-bot for Maxime Ripard <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, tglx@...utronix.de,
	maxime.ripard@...e-electrons.com, hdegoede@...hat.com,
	mingo@...nel.org, daniel.lezcano@...aro.org
Subject: [tip:timers/urgent] clocksource/drivers/sun5i:
  Fix cpufreq interaction with sched_clock()

Commit-ID:  6e206020324c50a95486f6b279a53512febed92d
Gitweb:     http://git.kernel.org/tip/6e206020324c50a95486f6b279a53512febed92d
Author:     Maxime Ripard <maxime.ripard@...e-electrons.com>
AuthorDate: Thu, 26 Mar 2015 10:27:09 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 26 Mar 2015 10:59:40 +0100

clocksource/drivers/sun5i: Fix cpufreq interaction with sched_clock()

The sun5i timer is used as the sched-clock on certain systems, and ever
since we started using cpufreq, the cpu clock (that is one of the
timer's clock indirect parent) now changes as well, along with the
actual sched_clock() rate.

This is not accurate and not desirable.

We can safely remove the sun5i sched-clock on those systems, since we
have other reliable sched_clock() sources in the system.

Tested-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
[ Improved the changelog. ]
Cc: richard@....at
Link: http://lkml.kernel.org/r/1427362029-6511-4-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 drivers/clocksource/timer-sun5i.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/clocksource/timer-sun5i.c b/drivers/clocksource/timer-sun5i.c
index 5dcbf90..58597fb 100644
--- a/drivers/clocksource/timer-sun5i.c
+++ b/drivers/clocksource/timer-sun5i.c
@@ -17,7 +17,6 @@
 #include <linux/irq.h>
 #include <linux/irqreturn.h>
 #include <linux/reset.h>
-#include <linux/sched_clock.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
@@ -137,11 +136,6 @@ static struct irqaction sun5i_timer_irq = {
 	.dev_id = &sun5i_clockevent,
 };
 
-static u64 sun5i_timer_sched_read(void)
-{
-	return ~readl(timer_base + TIMER_CNTVAL_LO_REG(1));
-}
-
 static void __init sun5i_timer_init(struct device_node *node)
 {
 	struct reset_control *rstc;
@@ -172,7 +166,6 @@ static void __init sun5i_timer_init(struct device_node *node)
 	writel(TIMER_CTL_ENABLE | TIMER_CTL_RELOAD,
 	       timer_base + TIMER_CTL_REG(1));
 
-	sched_clock_register(sun5i_timer_sched_read, 32, rate);
 	clocksource_mmio_init(timer_base + TIMER_CNTVAL_LO_REG(1), node->name,
 			      rate, 340, 32, clocksource_mmio_readl_down);
 
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