[PATCH 0/5] PM Fixes for exynos5

[PATCH 0/5] PM Fixes for exynos5

[Abhilash Kesavan]

This patchset comprises fixes to properly enable PM support on exynos5.
Based on git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux-samsung.git
for-next branch.

Patches 1 and 4 are re-posts of patches sent earlier by Changhwan Youn and
Inderpal Singh respectively. Links follow:
http://lists.infradead.org/pipermail/linux-arm-kernel/2012-May/098930.html
http://permalink.gmane.org/gmane.linux.kernel.samsung-soc/10947

Patch 2 is a fix in cpuidle while patch 3 enables the RTC alarm as a wake
up source.

Patch 5 adds a machine specific "flush_cache_all" as it is no longer part
of the core suspend routine. This was suggested by Lorenzo Pieralisi.

These patches have been tested on SMDK5250.

Abhilash Kesavan (3):
  ARM: EXYNOS: fix the hotplug for Cortex-A15
  ARM: EXYNOS5: Remove scu_enable from cpuidle
  ARM: EXYNOS5: Add flush_cache_all in suspend finisher

Inderpal Singh (2):
  ARM: EXYNOS5: Add support for rtc wakeup
  ARM: EXYNOS: Fix soft reboot hang after suspend/resume

 arch/arm/mach-exynos/common.c           |    2 +
 arch/arm/mach-exynos/cpuidle.c          |    3 +-
 arch/arm/mach-exynos/hotplug.c          |   45 ++++++++++++++++++++++++++++--
 arch/arm/mach-exynos/pm.c               |    7 +++++
 arch/arm/plat-samsung/include/plat/pm.h |    2 +
 5 files changed, 55 insertions(+), 4 deletions(-)

[PATCH 1/5] ARM: EXYNOS: fix the hotplug for Cortex-A15

[Abhilash Kesavan]

The sequence of cpu_enter_lowpower() for Cortex-A15
is different from the sequence for Cortex-A9.
This patch implements cpu_enter_lowpower() for EXYNOS5
SoC which has Cortex-A15 cores.

Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Tested-by: Abhilash Kesavan <a.kesavan@samsung.com>
---
 arch/arm/mach-exynos/hotplug.c |   45 +++++++++++++++++++++++++++++++++++++--
 1 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mach-exynos/hotplug.c b/arch/arm/mach-exynos/hotplug.c
index f4d7dd2..8c06c4f 100644
--- a/arch/arm/mach-exynos/hotplug.c
+++ b/arch/arm/mach-exynos/hotplug.c
@@ -20,10 +20,11 @@
 #include <asm/smp_plat.h>
 
 #include <mach/regs-pmu.h>
+#include <plat/cpu.h>
 
 #include "common.h"
 
-static inline void cpu_enter_lowpower(void)
+static inline void cpu_enter_lowpower_a9(void)
 {
 	unsigned int v;
 
@@ -45,6 +46,35 @@ static inline void cpu_enter_lowpower(void)
 	  : "cc");
 }
 
+static inline void cpu_enter_lowpower_a15(void)
+{
+	unsigned int v;
+
+	asm volatile(
+	"	mrc	p15, 0, %0, c1, c0, 0\n"
+	"	bic	%0, %0, %1\n"
+	"	mcr	p15, 0, %0, c1, c0, 0\n"
+	  : "=&r" (v)
+	  : "Ir" (CR_C)
+	  : "cc");
+
+	flush_cache_all();
+
+	asm volatile(
+	/*
+	* Turn off coherency
+	*/
+	"	mrc	p15, 0, %0, c1, c0, 1\n"
+	"	bic	%0, %0, %1\n"
+	"	mcr	p15, 0, %0, c1, c0, 1\n"
+	: "=&r" (v)
+	: "Ir" (0x40)
+	: "cc");
+
+	isb();
+	dsb();
+}
+
 static inline void cpu_leave_lowpower(void)
 {
 	unsigned int v;
@@ -103,11 +133,20 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
 void __ref exynos_cpu_die(unsigned int cpu)
 {
 	int spurious = 0;
+	int primary_part = 0;
 
 	/*
-	 * we're ready for shutdown now, so do it
+	 * we're ready for shutdown now, so do it.
+	 * Exynos4 is A9 based while Exynos5 is A15; check the CPU part
+	 * number by reading the Main ID register and then perform the
+	 * appropriate sequence for entering low power.
 	 */
-	cpu_enter_lowpower();
+	asm("mrc p15, 0, %0, c0, c0, 0" : "=r"(primary_part) : : "cc");
+	if ((primary_part & 0xfff0) == 0xc0f0)
+		cpu_enter_lowpower_a15();
+	else
+		cpu_enter_lowpower_a9();
+
 	platform_do_lowpower(cpu, &spurious);
 
 	/*
-- 
1.6.6.1

[PATCH 2/5] ARM: EXYNOS5: Add support for rtc wakeup

[Abhilash Kesavan]

From: Inderpal Singh <inderpal.singh@samsung.com>

Set the gic arch extension callback to support rtc wakeup.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Signed-off-by: Inderpal Singh <inderpal.singh@samsung.com>
---
 arch/arm/mach-exynos/common.c           |    2 ++
 arch/arm/plat-samsung/include/plat/pm.h |    2 ++
 2 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-exynos/common.c b/arch/arm/mach-exynos/common.c
index 4e577f6..300c40f 100644
--- a/arch/arm/mach-exynos/common.c
+++ b/arch/arm/mach-exynos/common.c
@@ -631,6 +631,8 @@ void __init exynos5_init_irq(void)
 	 * uses GIC instead of VIC.
 	 */
 	s5p_init_irq(NULL, 0);
+
+	gic_arch_extn.irq_set_wake = s3c_irq_wake;
 }
 
 struct bus_type exynos_subsys = {
diff --git a/arch/arm/plat-samsung/include/plat/pm.h b/arch/arm/plat-samsung/include/plat/pm.h
index 61fc537..887a0c9 100644
--- a/arch/arm/plat-samsung/include/plat/pm.h
+++ b/arch/arm/plat-samsung/include/plat/pm.h
@@ -107,10 +107,12 @@ extern void s3c_pm_do_restore(struct sleep_save *ptr, int count);
 extern void s3c_pm_do_restore_core(struct sleep_save *ptr, int count);
 
 #ifdef CONFIG_PM
+extern int s3c_irq_wake(struct irq_data *data, unsigned int state);
 extern int s3c_irqext_wake(struct irq_data *data, unsigned int state);
 extern int s3c24xx_irq_suspend(void);
 extern void s3c24xx_irq_resume(void);
 #else
+#define s3c_irq_wake NULL
 #define s3c_irqext_wake NULL
 #define s3c24xx_irq_suspend NULL
 #define s3c24xx_irq_resume  NULL
-- 
1.6.6.1

[PATCH 3/5] ARM: EXYNOS: Fix soft reboot hang after suspend/resume

[Abhilash Kesavan]

From: Inderpal Singh <inderpal.singh@samsung.com>

Upon wake-up, clear the sleep mode set in INFORM1 register.

Signed-off-by: Inderpal Singh <inderpal.singh@samsung.com>
Tested-by: Abhilash Kesavan <a.kesavan@samsung.com>
---
 arch/arm/mach-exynos/pm.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-exynos/pm.c b/arch/arm/mach-exynos/pm.c
index c06c992..8dedeb2 100644
--- a/arch/arm/mach-exynos/pm.c
+++ b/arch/arm/mach-exynos/pm.c
@@ -312,6 +312,10 @@ static void exynos_pm_resume(void)
 	}
 
 early_wakeup:
+
+	/* Clear SLEEP mode set in INFORM1 */
+	__raw_writel(0x0, S5P_INFORM1);
+
 	return;
 }
 
-- 
1.6.6.1

[PATCH 4/5] ARM: EXYNOS5: Remove scu_enable from cpuidle

[Abhilash Kesavan]

Cortex A9 based exynos4 has a memory mapped SCU while the Cortex
A15 based exynos5 does not. Hence, remove the call to scu_enable
for exynos5.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Signed-off-by: Inderpal Singh <inderpal.singh@samsung.com>
---
 arch/arm/mach-exynos/cpuidle.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mach-exynos/cpuidle.c b/arch/arm/mach-exynos/cpuidle.c
index cff0595..8e4ec21 100644
--- a/arch/arm/mach-exynos/cpuidle.c
+++ b/arch/arm/mach-exynos/cpuidle.c
@@ -116,7 +116,8 @@ static int exynos4_enter_core0_aftr(struct cpuidle_device *dev,
 	cpu_suspend(0, idle_finisher);
 
 #ifdef CONFIG_SMP
-	scu_enable(S5P_VA_SCU);
+	if (!soc_is_exynos5250())
+		scu_enable(S5P_VA_SCU);
 #endif
 	cpu_pm_exit();
 
-- 
1.6.6.1

[PATCH 5/5] ARM: EXYNOS5: Add flush_cache_all in suspend finisher

[Abhilash Kesavan]

The core cpu_suspend code no longer calls flush_cache_all to
optimize the cpu idle flow. Add a call for the same in the
exynos specific suspend code.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
---
 arch/arm/mach-exynos/pm.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-exynos/pm.c b/arch/arm/mach-exynos/pm.c
index 8dedeb2..8df6ec5 100644
--- a/arch/arm/mach-exynos/pm.c
+++ b/arch/arm/mach-exynos/pm.c
@@ -81,6 +81,9 @@ static int exynos_cpu_suspend(unsigned long arg)
 	outer_flush_all();
 #endif
 
+	if (soc_is_exynos5250())
+		flush_cache_all();
+
 	/* issue the standby signal into the pm unit. */
 	cpu_do_idle();
 
-- 
1.6.6.1

[PATCH 1/5] ARM: EXYNOS: fix the hotplug for Cortex-A15

[Kyungmin Park]

Hi,

On 11/6/12, Abhilash Kesavan <a.kesavan@samsung.com> wrote:
> The sequence of cpu_enter_lowpower() for Cortex-A15
> is different from the sequence for Cortex-A9.
> This patch implements cpu_enter_lowpower() for EXYNOS5
> SoC which has Cortex-A15 cores.
>
> Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
> Cc: Russell King <rmk+kernel@arm.linux.org.uk>
> Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
> Tested-by: Abhilash Kesavan <a.kesavan@samsung.com>
> ---
>  arch/arm/mach-exynos/hotplug.c |   45
> +++++++++++++++++++++++++++++++++++++--
>  1 files changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/mach-exynos/hotplug.c
> b/arch/arm/mach-exynos/hotplug.c
> index f4d7dd2..8c06c4f 100644
> --- a/arch/arm/mach-exynos/hotplug.c
> +++ b/arch/arm/mach-exynos/hotplug.c
> @@ -20,10 +20,11 @@
>  #include <asm/smp_plat.h>
>
>  #include <mach/regs-pmu.h>
> +#include <plat/cpu.h>
>
>  #include "common.h"
>
> -static inline void cpu_enter_lowpower(void)
> +static inline void cpu_enter_lowpower_a9(void)
>  {
>  	unsigned int v;
>
> @@ -45,6 +46,35 @@ static inline void cpu_enter_lowpower(void)
>  	  : "cc");
>  }
>
> +static inline void cpu_enter_lowpower_a15(void)
> +{
> +	unsigned int v;
> +
> +	asm volatile(
> +	"	mrc	p15, 0, %0, c1, c0, 0\n"
> +	"	bic	%0, %0, %1\n"
> +	"	mcr	p15, 0, %0, c1, c0, 0\n"
> +	  : "=&r" (v)
> +	  : "Ir" (CR_C)
> +	  : "cc");
> +
> +	flush_cache_all();
> +
> +	asm volatile(
> +	/*
> +	* Turn off coherency
> +	*/
> +	"	mrc	p15, 0, %0, c1, c0, 1\n"
> +	"	bic	%0, %0, %1\n"
> +	"	mcr	p15, 0, %0, c1, c0, 1\n"
> +	: "=&r" (v)
> +	: "Ir" (0x40)
> +	: "cc");
> +
> +	isb();
> +	dsb();
> +}
> +
>  static inline void cpu_leave_lowpower(void)
>  {
>  	unsigned int v;
> @@ -103,11 +133,20 @@ static inline void platform_do_lowpower(unsigned int
> cpu, int *spurious)
>  void __ref exynos_cpu_die(unsigned int cpu)
>  {
>  	int spurious = 0;
> +	int primary_part = 0;
>
>  	/*
> -	 * we're ready for shutdown now, so do it
> +	 * we're ready for shutdown now, so do it.
> +	 * Exynos4 is A9 based while Exynos5 is A15; check the CPU part
> +	 * number by reading the Main ID register and then perform the
> +	 * appropriate sequence for entering low power.
>  	 */
> -	cpu_enter_lowpower();
> +	asm("mrc p15, 0, %0, c0, c0, 0" : "=r"(primary_part) : : "cc");
> +	if ((primary_part & 0xfff0) == 0xc0f0)
Doesn't better to use soc_is_exynos5250? Actullay, it's better to use
soc_is_exynos5 for all exynos5 series. but not it doesn't have these
macro.

Thank you,
Kyungmin Park
> +		cpu_enter_lowpower_a15();
> +	else
> +		cpu_enter_lowpower_a9();
> +
>  	platform_do_lowpower(cpu, &spurious);
>
>  	/*
> --
> 1.6.6.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

[PATCH 1/5] ARM: EXYNOS: fix the hotplug for Cortex-A15

[Santosh Shilimkar]

On Tuesday 06 November 2012 12:12 AM, Abhilash Kesavan wrote:
> The sequence of cpu_enter_lowpower() for Cortex-A15
> is different from the sequence for Cortex-A9.
Are you sure ? Apart from integrated cache vs external, there
should be no change. And L2 doesn't need to come into picture
while powering down just a CPU.

> This patch implements cpu_enter_lowpower() for EXYNOS5
> SoC which has Cortex-A15 cores.
>
> Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
> Cc: Russell King <rmk+kernel@arm.linux.org.uk>
> Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
> Tested-by: Abhilash Kesavan <a.kesavan@samsung.com>
> ---
>   arch/arm/mach-exynos/hotplug.c |   45 +++++++++++++++++++++++++++++++++++++--
>   1 files changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/mach-exynos/hotplug.c b/arch/arm/mach-exynos/hotplug.c
> index f4d7dd2..8c06c4f 100644
> --- a/arch/arm/mach-exynos/hotplug.c
> +++ b/arch/arm/mach-exynos/hotplug.c
> @@ -20,10 +20,11 @@
>   #include <asm/smp_plat.h>
>
>   #include <mach/regs-pmu.h>
> +#include <plat/cpu.h>
>
>   #include "common.h"
>
> -static inline void cpu_enter_lowpower(void)
> +static inline void cpu_enter_lowpower_a9(void)
>   {
>   	unsigned int v;
>
> @@ -45,6 +46,35 @@ static inline void cpu_enter_lowpower(void)
>   	  : "cc");
>   }
>
> +static inline void cpu_enter_lowpower_a15(void)
> +{
> +	unsigned int v;
> +
> +	asm volatile(
> +	"	mrc	p15, 0, %0, c1, c0, 0\n"
> +	"	bic	%0, %0, %1\n"
> +	"	mcr	p15, 0, %0, c1, c0, 0\n"
> +	  : "=&r" (v)
> +	  : "Ir" (CR_C)
> +	  : "cc");
> +
> +	flush_cache_all();
> +
Why are flushing all the cache levels ?
flush_kern_louis() should be enough for CPU power
down.

> +	asm volatile(
> +	/*
> +	* Turn off coherency
> +	*/
> +	"	mrc	p15, 0, %0, c1, c0, 1\n"
> +	"	bic	%0, %0, %1\n"
> +	"	mcr	p15, 0, %0, c1, c0, 1\n"
> +	: "=&r" (v)
> +	: "Ir" (0x40)
> +	: "cc");
> +
> +	isb();
> +	dsb();
> +}
> +
The above sequence should work on A9 as well. In general you should have
CPU power down code under one code block and avoid making use of stack 
in between. Otherwise you will end up with stack corruption because of
the memory view change after C bit is disabled.

Regards
Santosh

[PATCH 1/5] ARM: EXYNOS: fix the hotplug for Cortex-A15

[Lorenzo Pieralisi]

On Tue, Nov 06, 2012 at 12:17:02PM +0000, Santosh Shilimkar wrote:
> On Tuesday 06 November 2012 12:12 AM, Abhilash Kesavan wrote:
> > The sequence of cpu_enter_lowpower() for Cortex-A15
> > is different from the sequence for Cortex-A9.
> Are you sure ? Apart from integrated cache vs external, there
> should be no change. And L2 doesn't need to come into picture
> while powering down just a CPU.

Reiterating Santosh point in here. v7 shutdown procedure is and has to
be identical across all v7 cores. There is not such a thing as "A15
specific" shutdown procedure.

Embedded L2 will come into the picture on multi-cluster systems, for the
time being L2 must not be flushed when hotplugging a CPU in a single cluster
so the LoUIS API is to be used here.

> > This patch implements cpu_enter_lowpower() for EXYNOS5
> > SoC which has Cortex-A15 cores.
> >
> > Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
> > Cc: Russell King <rmk+kernel@arm.linux.org.uk>
> > Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
> > Tested-by: Abhilash Kesavan <a.kesavan@samsung.com>
> > ---
> >   arch/arm/mach-exynos/hotplug.c |   45 +++++++++++++++++++++++++++++++++++++--
> >   1 files changed, 42 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm/mach-exynos/hotplug.c b/arch/arm/mach-exynos/hotplug.c
> > index f4d7dd2..8c06c4f 100644
> > --- a/arch/arm/mach-exynos/hotplug.c
> > +++ b/arch/arm/mach-exynos/hotplug.c
> > @@ -20,10 +20,11 @@
> >   #include <asm/smp_plat.h>
> >
> >   #include <mach/regs-pmu.h>
> > +#include <plat/cpu.h>
> >
> >   #include "common.h"
> >
> > -static inline void cpu_enter_lowpower(void)
> > +static inline void cpu_enter_lowpower_a9(void)
> >   {
> >   	unsigned int v;
> >
> > @@ -45,6 +46,35 @@ static inline void cpu_enter_lowpower(void)
> >   	  : "cc");
> >   }
> >
> > +static inline void cpu_enter_lowpower_a15(void)
> > +{
> > +	unsigned int v;
> > +
> > +	asm volatile(
> > +	"	mrc	p15, 0, %0, c1, c0, 0\n"
> > +	"	bic	%0, %0, %1\n"
> > +	"	mcr	p15, 0, %0, c1, c0, 0\n"
> > +	  : "=&r" (v)
> > +	  : "Ir" (CR_C)
> > +	  : "cc");
> > +
> > +	flush_cache_all();
> > +
> Why are flushing all the cache levels ?
> flush_kern_louis() should be enough for CPU power
> down.

Agree with Santosh again.

> 
> > +	asm volatile(
> > +	/*
> > +	* Turn off coherency
> > +	*/
> > +	"	mrc	p15, 0, %0, c1, c0, 1\n"
> > +	"	bic	%0, %0, %1\n"
> > +	"	mcr	p15, 0, %0, c1, c0, 1\n"
> > +	: "=&r" (v)
> > +	: "Ir" (0x40)
> > +	: "cc");
> > +
> > +	isb();
> > +	dsb();
> > +}
> > +
> The above sequence should work on A9 as well. In general you should have
> CPU power down code under one code block and avoid making use of stack 
> in between. Otherwise you will end up with stack corruption because of
> the memory view change after C bit is disabled.
> 
> Regards
> Santosh

The above sequence does not work on A9 since A9 does not look-up the
caches when the C bit is cleared. It is an accident waiting to happen,
as Santosh explained.

The sequence:

- clear C bit
- clean L1
- exit SMP

must be written in assembly with no access to any data whatsoever, no stack,
_nothing_.

There is some code in the works to consolidate this procedure once for all but
all bits and pieces are already in the kernel.

Lorenzo

[PATCH 1/5] ARM: EXYNOS: fix the hotplug for Cortex-A15

[Kukjin Kim]

Lorenzo Pieralisi wrote:
> 
> On Tue, Nov 06, 2012 at 12:17:02PM +0000, Santosh Shilimkar wrote:
> > On Tuesday 06 November 2012 12:12 AM, Abhilash Kesavan wrote:
> > > The sequence of cpu_enter_lowpower() for Cortex-A15
> > > is different from the sequence for Cortex-A9.
> > Are you sure ? Apart from integrated cache vs external, there
> > should be no change. And L2 doesn't need to come into picture
> > while powering down just a CPU.
> 
> Reiterating Santosh point in here. v7 shutdown procedure is and has to
> be identical across all v7 cores. There is not such a thing as "A15
> specific" shutdown procedure.
> 
BTW, it's true that current codes cannot support A15. So we need a separate
A15 func. And a A9 func. Now, cpu_enter_lowpower_a9() on A15 does NOT
work...also cpu_enter_lowpower_a15() on A9 does NOT work as well...

> Embedded L2 will come into the picture on multi-cluster systems, for the
> time being L2 must not be flushed when hotplugging a CPU in a single
> cluster
> so the LoUIS API is to be used here.
> 
OK.

> > > This patch implements cpu_enter_lowpower() for EXYNOS5
> > > SoC which has Cortex-A15 cores.

[...]

> > >
> > > +static inline void cpu_enter_lowpower_a15(void)
> > > +{
> > > +	unsigned int v;
> > > +
> > > +	asm volatile(
> > > +	"	mrc	p15, 0, %0, c1, c0, 0\n"
> > > +	"	bic	%0, %0, %1\n"
> > > +	"	mcr	p15, 0, %0, c1, c0, 0\n"
> > > +	  : "=&r" (v)
> > > +	  : "Ir" (CR_C)
> > > +	  : "cc");
> > > +
> > > +	flush_cache_all();
> > > +
> > Why are flushing all the cache levels ?
> > flush_kern_louis() should be enough for CPU power
> > down.
> 
> Agree with Santosh again.
> 
Yes, agree. I will replace as per your suggestion when I apply this. And as
I know, Abhilash already tested it on the boards and it works fine.

> >
> > > +	asm volatile(
> > > +	/*
> > > +	* Turn off coherency
> > > +	*/
> > > +	"	mrc	p15, 0, %0, c1, c0, 1\n"
> > > +	"	bic	%0, %0, %1\n"
> > > +	"	mcr	p15, 0, %0, c1, c0, 1\n"
> > > +	: "=&r" (v)
> > > +	: "Ir" (0x40)
> > > +	: "cc");
> > > +
> > > +	isb();
> > > +	dsb();
> > > +}
> > > +
> > The above sequence should work on A9 as well. In general you should have
> > CPU power down code under one code block and avoid making use of stack
> > in between. Otherwise you will end up with stack corruption because of
> > the memory view change after C bit is disabled.
> >
> > Regards
> > Santosh
> 
> The above sequence does not work on A9 since A9 does not look-up the
> caches when the C bit is cleared. It is an accident waiting to happen,
> as Santosh explained.
> 
> The sequence:
> 
> - clear C bit
> - clean L1
> - exit SMP
> 
> must be written in assembly with no access to any data whatsoever, no
> stack,
> _nothing_.
> 
> There is some code in the works to consolidate this procedure once for all
> but
> all bits and pieces are already in the kernel.
> 
I see, so it means, at this moment, exynos stuff needs this patch until
finishing common implementation you said. Then, I think, if any common codes
are available, we can use new codes instead.

K-Gene <kgene@kernel.org>