linux-kernel - [PATCH v2] xen/arm: disable cpuidle and cpufreq when linux is running as dom0

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Date:	Fri, 19 Jul 2013 12:27:00 +0100
From:	Julien Grall <julien.grall@...aro.org>
To:	stefano.stabellini@...citrix.com
Cc:	ian.campbell@...rix.com, patches@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xen.org, konrad.wilk@...cle.com,
	Julien Grall <julien.grall@...aro.org>
Subject: [PATCH v2] xen/arm: disable cpuidle and cpufreq when linux is running as dom0

When linux is running as dom0, Xen doesn't show the physical cpu but a
virtual CPU.
On some ARM SOC (for instance the exynos 5250), linux registers callbacks
for cpuidle and cpufreq. When these callbacks are called, they will modify
directly the physical cpu not the virtual one. It can impact the whole board
instead of only dom0.

Signed-off-by: Julien Grall <julien.grall@...aro.org>

---
    Changes in v2:
        - Disable cpufreq
---
 arch/arm/xen/enlighten.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 49839d8..af82792 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -24,6 +24,8 @@
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_address.h>
+#include <linux/cpuidle.h>
+#include <linux/cpufreq.h>
 
 #include <linux/mm.h>
 
@@ -292,6 +294,12 @@ static int __init xen_pm_init(void)
 {
 	pm_power_off = xen_power_off;
 	arm_pm_restart = xen_restart;
+	/*
+	 * Making sure board specific code will not set up ops for
+	 * cpu idle and cpu freq.
+	 */
+	disable_cpuidle();
+	disable_cpufreq();
 
 	return 0;
 }
-- 
1.7.10.4

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