[PATCH v3 1/2] ARM: EXYNOS: Fix failed second suspend on Exynos4

[PATCH v3 1/2] ARM: EXYNOS: Fix failed second suspend on Exynos4

[Krzysztof Kozlowski]

On Exynos4412 boards (Trats2, Odroid U3) after enabling L2 cache in
56b60b8bce4a ("ARM: 8265/1: dts: exynos4: Add nodes for L2 cache
controller") the second suspend to RAM failed. First suspend worked fine
but the next one hang just after powering down of secondary CPUs (system
consumed energy as it would be running but was not responsive).

The issue was caused by enabling delayed reset assertion for CPU0 just
after issuing power down of cores. This was introduced for Exynos4 in
13cfa6c4f7fa ("ARM: EXYNOS: Fix CPU idle clock down after CPU off").

The whole behavior is not well documented but after checking with vendor
code this should be done like this (on Exynos4):
1. Enable delayed reset assertion when system is running (for all CPUs).
2. Disable delayed reset assertion before suspending the system.
   This can be done after powering off secondary CPUs.
3. Re-enable the delayed reset assertion when system is resumed.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Fixes: 13cfa6c4f7fa ("ARM: EXYNOS: Fix CPU idle clock down after CPU off")
Cc: <stable@vger.kernel.org>
Tested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>

---
Changes since v2:
None.
---
 arch/arm/mach-exynos/common.h  |  2 ++
 arch/arm/mach-exynos/exynos.c  | 27 +++++++++++++++++++++++++++
 arch/arm/mach-exynos/platsmp.c | 39 ++-------------------------------------
 arch/arm/mach-exynos/suspend.c |  3 +++
 4 files changed, 34 insertions(+), 37 deletions(-)

diff --git a/arch/arm/mach-exynos/common.h b/arch/arm/mach-exynos/common.h
index acd5b560b728..5f5cd562c593 100644
--- a/arch/arm/mach-exynos/common.h
+++ b/arch/arm/mach-exynos/common.h
@@ -159,6 +159,8 @@ extern void exynos_enter_aftr(void);
 
 extern struct cpuidle_exynos_data cpuidle_coupled_exynos_data;
 
+extern void exynos_set_delayed_reset_assertion(bool enable);
+
 extern void s5p_init_cpu(void __iomem *cpuid_addr);
 extern unsigned int samsung_rev(void);
 extern void __iomem *cpu_boot_reg_base(void);
diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
index bcde0dd668df..c3bfbba3006d 100644
--- a/arch/arm/mach-exynos/exynos.c
+++ b/arch/arm/mach-exynos/exynos.c
@@ -167,6 +167,33 @@ static void __init exynos_init_io(void)
 }
 
 /*
+ * Set or clear the USE_DELAYED_RESET_ASSERTION option. Used by smp code
+ * and suspend.
+ *
+ * This is necessary only on Exynos4 SoCs. When system is running
+ * USE_DELAYED_RESET_ASSERTION should be set so the ARM CLK clock down
+ * feature could properly detect global idle state when secondary CPU is
+ * powered down.
+ *
+ * However this should not be set when such system is going into suspend.
+ */
+void exynos_set_delayed_reset_assertion(bool enable)
+{
+	if (soc_is_exynos4()) {
+		unsigned int tmp, core_id;
+
+		for (core_id = 0; core_id < num_possible_cpus(); core_id++) {
+			tmp = pmu_raw_readl(EXYNOS_ARM_CORE_OPTION(core_id));
+			if (enable)
+				tmp |= S5P_USE_DELAYED_RESET_ASSERTION;
+			else
+				tmp &= ~(S5P_USE_DELAYED_RESET_ASSERTION);
+			pmu_raw_writel(tmp, EXYNOS_ARM_CORE_OPTION(core_id));
+		}
+	}
+}
+
+/*
  * Apparently, these SoCs are not able to wake-up from suspend using
  * the PMU. Too bad. Should they suddenly become capable of such a
  * feat, the matches below should be moved to suspend.c.
diff --git a/arch/arm/mach-exynos/platsmp.c b/arch/arm/mach-exynos/platsmp.c
index ebd135bb0995..a825bca2a2b6 100644
--- a/arch/arm/mach-exynos/platsmp.c
+++ b/arch/arm/mach-exynos/platsmp.c
@@ -34,30 +34,6 @@
 
 extern void exynos4_secondary_startup(void);
 
-/*
- * Set or clear the USE_DELAYED_RESET_ASSERTION option, set on Exynos4 SoCs
- * during hot-(un)plugging CPUx.
- *
- * The feature can be cleared safely during first boot of secondary CPU.
- *
- * Exynos4 SoCs require setting USE_DELAYED_RESET_ASSERTION during powering
- * down a CPU so the CPU idle clock down feature could properly detect global
- * idle state when CPUx is off.
- */
-static void exynos_set_delayed_reset_assertion(u32 core_id, bool enable)
-{
-	if (soc_is_exynos4()) {
-		unsigned int tmp;
-
-		tmp = pmu_raw_readl(EXYNOS_ARM_CORE_OPTION(core_id));
-		if (enable)
-			tmp |= S5P_USE_DELAYED_RESET_ASSERTION;
-		else
-			tmp &= ~(S5P_USE_DELAYED_RESET_ASSERTION);
-		pmu_raw_writel(tmp, EXYNOS_ARM_CORE_OPTION(core_id));
-	}
-}
-
 #ifdef CONFIG_HOTPLUG_CPU
 static inline void cpu_leave_lowpower(u32 core_id)
 {
@@ -73,8 +49,6 @@ static inline void cpu_leave_lowpower(u32 core_id)
 	  : "=&r" (v)
 	  : "Ir" (CR_C), "Ir" (0x40)
 	  : "cc");
-
-	 exynos_set_delayed_reset_assertion(core_id, false);
 }
 
 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
@@ -87,14 +61,6 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
 		/* Turn the CPU off on next WFI instruction. */
 		exynos_cpu_power_down(core_id);
 
-		/*
-		 * Exynos4 SoCs require setting
-		 * USE_DELAYED_RESET_ASSERTION so the CPU idle
-		 * clock down feature could properly detect
-		 * global idle state when CPUx is off.
-		 */
-		exynos_set_delayed_reset_assertion(core_id, true);
-
 		wfi();
 
 		if (pen_release == core_id) {
@@ -371,9 +337,6 @@ static int exynos_boot_secondary(unsigned int cpu, struct task_struct *idle)
 		udelay(10);
 	}
 
-	/* No harm if this is called during first boot of secondary CPU */
-	exynos_set_delayed_reset_assertion(core_id, false);
-
 	/*
 	 * now the secondary core is starting up let it run its
 	 * calibrations, then wait for it to finish
@@ -420,6 +383,8 @@ static void __init exynos_smp_prepare_cpus(unsigned int max_cpus)
 
 	exynos_sysram_init();
 
+	exynos_set_delayed_reset_assertion(true);
+
 	if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9)
 		scu_enable(scu_base_addr());
 
diff --git a/arch/arm/mach-exynos/suspend.c b/arch/arm/mach-exynos/suspend.c
index 3e6aea7f83af..6fcc1fef695c 100644
--- a/arch/arm/mach-exynos/suspend.c
+++ b/arch/arm/mach-exynos/suspend.c
@@ -342,6 +342,8 @@ static void exynos_pm_enter_sleep_mode(void)
 
 static void exynos_pm_prepare(void)
 {
+	exynos_set_delayed_reset_assertion(false);
+
 	/* Set wake-up mask registers */
 	exynos_pm_set_wakeup_mask();
 
@@ -482,6 +484,7 @@ early_wakeup:
 
 	/* Clear SLEEP mode set in INFORM1 */
 	pmu_raw_writel(0x0, S5P_INFORM1);
+	exynos_set_delayed_reset_assertion(true);
 }
 
 static void exynos3250_pm_resume(void)
-- 
1.9.1

[PATCH v3 1/2] ARM: EXYNOS: Fix failed second suspend on Exynos4

[Krzysztof Kozlowski]

On Exynos4412 boards (Trats2, Odroid U3) after enabling L2 cache in
56b60b8bce4a ("ARM: 8265/1: dts: exynos4: Add nodes for L2 cache
controller") the second suspend to RAM failed. First suspend worked fine
but the next one hang just after powering down of secondary CPUs (system
consumed energy as it would be running but was not responsive).

The issue was caused by enabling delayed reset assertion for CPU0 just
after issuing power down of cores. This was introduced for Exynos4 in
13cfa6c4f7fa ("ARM: EXYNOS: Fix CPU idle clock down after CPU off").

The whole behavior is not well documented but after checking with vendor
code this should be done like this (on Exynos4):
1. Enable delayed reset assertion when system is running (for all CPUs).
2. Disable delayed reset assertion before suspending the system.
   This can be done after powering off secondary CPUs.
3. Re-enable the delayed reset assertion when system is resumed.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Fixes: 13cfa6c4f7fa ("ARM: EXYNOS: Fix CPU idle clock down after CPU off")
Cc: <stable@vger.kernel.org>
Tested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>

---
Changes since v2:
None.
---
 arch/arm/mach-exynos/common.h  |  2 ++
 arch/arm/mach-exynos/exynos.c  | 27 +++++++++++++++++++++++++++
 arch/arm/mach-exynos/platsmp.c | 39 ++-------------------------------------
 arch/arm/mach-exynos/suspend.c |  3 +++
 4 files changed, 34 insertions(+), 37 deletions(-)

diff --git a/arch/arm/mach-exynos/common.h b/arch/arm/mach-exynos/common.h
index acd5b560b728..5f5cd562c593 100644
--- a/arch/arm/mach-exynos/common.h
+++ b/arch/arm/mach-exynos/common.h
@@ -159,6 +159,8 @@ extern void exynos_enter_aftr(void);
 
 extern struct cpuidle_exynos_data cpuidle_coupled_exynos_data;
 
+extern void exynos_set_delayed_reset_assertion(bool enable);
+
 extern void s5p_init_cpu(void __iomem *cpuid_addr);
 extern unsigned int samsung_rev(void);
 extern void __iomem *cpu_boot_reg_base(void);
diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
index bcde0dd668df..c3bfbba3006d 100644
--- a/arch/arm/mach-exynos/exynos.c
+++ b/arch/arm/mach-exynos/exynos.c
@@ -167,6 +167,33 @@ static void __init exynos_init_io(void)
 }
 
 /*
+ * Set or clear the USE_DELAYED_RESET_ASSERTION option. Used by smp code
+ * and suspend.
+ *
+ * This is necessary only on Exynos4 SoCs. When system is running
+ * USE_DELAYED_RESET_ASSERTION should be set so the ARM CLK clock down
+ * feature could properly detect global idle state when secondary CPU is
+ * powered down.
+ *
+ * However this should not be set when such system is going into suspend.
+ */
+void exynos_set_delayed_reset_assertion(bool enable)
+{
+	if (soc_is_exynos4()) {
+		unsigned int tmp, core_id;
+
+		for (core_id = 0; core_id < num_possible_cpus(); core_id++) {
+			tmp = pmu_raw_readl(EXYNOS_ARM_CORE_OPTION(core_id));
+			if (enable)
+				tmp |= S5P_USE_DELAYED_RESET_ASSERTION;
+			else
+				tmp &= ~(S5P_USE_DELAYED_RESET_ASSERTION);
+			pmu_raw_writel(tmp, EXYNOS_ARM_CORE_OPTION(core_id));
+		}
+	}
+}
+
+/*
  * Apparently, these SoCs are not able to wake-up from suspend using
  * the PMU. Too bad. Should they suddenly become capable of such a
  * feat, the matches below should be moved to suspend.c.
diff --git a/arch/arm/mach-exynos/platsmp.c b/arch/arm/mach-exynos/platsmp.c
index ebd135bb0995..a825bca2a2b6 100644
--- a/arch/arm/mach-exynos/platsmp.c
+++ b/arch/arm/mach-exynos/platsmp.c
@@ -34,30 +34,6 @@
 
 extern void exynos4_secondary_startup(void);
 
-/*
- * Set or clear the USE_DELAYED_RESET_ASSERTION option, set on Exynos4 SoCs
- * during hot-(un)plugging CPUx.
- *
- * The feature can be cleared safely during first boot of secondary CPU.
- *
- * Exynos4 SoCs require setting USE_DELAYED_RESET_ASSERTION during powering
- * down a CPU so the CPU idle clock down feature could properly detect global
- * idle state when CPUx is off.
- */
-static void exynos_set_delayed_reset_assertion(u32 core_id, bool enable)
-{
-	if (soc_is_exynos4()) {
-		unsigned int tmp;
-
-		tmp = pmu_raw_readl(EXYNOS_ARM_CORE_OPTION(core_id));
-		if (enable)
-			tmp |= S5P_USE_DELAYED_RESET_ASSERTION;
-		else
-			tmp &= ~(S5P_USE_DELAYED_RESET_ASSERTION);
-		pmu_raw_writel(tmp, EXYNOS_ARM_CORE_OPTION(core_id));
-	}
-}
-
 #ifdef CONFIG_HOTPLUG_CPU
 static inline void cpu_leave_lowpower(u32 core_id)
 {
@@ -73,8 +49,6 @@ static inline void cpu_leave_lowpower(u32 core_id)
 	  : "=&r" (v)
 	  : "Ir" (CR_C), "Ir" (0x40)
 	  : "cc");
-
-	 exynos_set_delayed_reset_assertion(core_id, false);
 }
 
 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
@@ -87,14 +61,6 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
 		/* Turn the CPU off on next WFI instruction. */
 		exynos_cpu_power_down(core_id);
 
-		/*
-		 * Exynos4 SoCs require setting
-		 * USE_DELAYED_RESET_ASSERTION so the CPU idle
-		 * clock down feature could properly detect
-		 * global idle state when CPUx is off.
-		 */
-		exynos_set_delayed_reset_assertion(core_id, true);
-
 		wfi();
 
 		if (pen_release == core_id) {
@@ -371,9 +337,6 @@ static int exynos_boot_secondary(unsigned int cpu, struct task_struct *idle)
 		udelay(10);
 	}
 
-	/* No harm if this is called during first boot of secondary CPU */
-	exynos_set_delayed_reset_assertion(core_id, false);
-
 	/*
 	 * now the secondary core is starting up let it run its
 	 * calibrations, then wait for it to finish
@@ -420,6 +383,8 @@ static void __init exynos_smp_prepare_cpus(unsigned int max_cpus)
 
 	exynos_sysram_init();
 
+	exynos_set_delayed_reset_assertion(true);
+
 	if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9)
 		scu_enable(scu_base_addr());
 
diff --git a/arch/arm/mach-exynos/suspend.c b/arch/arm/mach-exynos/suspend.c
index 3e6aea7f83af..6fcc1fef695c 100644
--- a/arch/arm/mach-exynos/suspend.c
+++ b/arch/arm/mach-exynos/suspend.c
@@ -342,6 +342,8 @@ static void exynos_pm_enter_sleep_mode(void)
 
 static void exynos_pm_prepare(void)
 {
+	exynos_set_delayed_reset_assertion(false);
+
 	/* Set wake-up mask registers */
 	exynos_pm_set_wakeup_mask();
 
@@ -482,6 +484,7 @@ early_wakeup:
 
 	/* Clear SLEEP mode set in INFORM1 */
 	pmu_raw_writel(0x0, S5P_INFORM1);
+	exynos_set_delayed_reset_assertion(true);
 }
 
 static void exynos3250_pm_resume(void)
-- 
1.9.1

[PATCH v3 2/2] ARM: EXYNOS: Use of_machine_is_compatible instead of soc_is_exynos4

[Krzysztof Kozlowski]

of_machine_is_compatible() seems to be preferred over soc_is_exynos4().

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

---
Changes since v2:
1. New patch, requested by Kukjin Kim.
---
 arch/arm/mach-exynos/exynos.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
index c3bfbba3006d..5917a30eee33 100644
--- a/arch/arm/mach-exynos/exynos.c
+++ b/arch/arm/mach-exynos/exynos.c
@@ -179,7 +179,7 @@ static void __init exynos_init_io(void)
  */
 void exynos_set_delayed_reset_assertion(bool enable)
 {
-	if (soc_is_exynos4()) {
+	if (of_machine_is_compatible("samsung,exynos4")) {
 		unsigned int tmp, core_id;
 
 		for (core_id = 0; core_id < num_possible_cpus(); core_id++) {
-- 
1.9.1

[PATCH v3 2/2] ARM: EXYNOS: Use of_machine_is_compatible instead of soc_is_exynos4

[Krzysztof Kozlowski]

of_machine_is_compatible() seems to be preferred over soc_is_exynos4().

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

---
Changes since v2:
1. New patch, requested by Kukjin Kim.
---
 arch/arm/mach-exynos/exynos.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
index c3bfbba3006d..5917a30eee33 100644
--- a/arch/arm/mach-exynos/exynos.c
+++ b/arch/arm/mach-exynos/exynos.c
@@ -179,7 +179,7 @@ static void __init exynos_init_io(void)
  */
 void exynos_set_delayed_reset_assertion(bool enable)
 {
-	if (soc_is_exynos4()) {
+	if (of_machine_is_compatible("samsung,exynos4")) {
 		unsigned int tmp, core_id;
 
 		for (core_id = 0; core_id < num_possible_cpus(); core_id++) {
-- 
1.9.1

Re: [PATCH v3 2/2] ARM: EXYNOS: Use of_machine_is_compatible instead ofsoc_is_exynos4

[Kukjin Kim]

On 05/11/15 10:27, Krzysztof Kozlowski wrote:
> of_machine_is_compatible() seems to be preferred over soc_is_exynos4().
> 
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> 
> ---
> Changes since v2:
> 1. New patch, requested by Kukjin Kim.
> ---
>  arch/arm/mach-exynos/exynos.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
> index c3bfbba3006d..5917a30eee33 100644
> --- a/arch/arm/mach-exynos/exynos.c
> +++ b/arch/arm/mach-exynos/exynos.c
> @@ -179,7 +179,7 @@ static void __init exynos_init_io(void)
>   */
>  void exynos_set_delayed_reset_assertion(bool enable)
>  {
> -	if (soc_is_exynos4()) {
> +	if (of_machine_is_compatible("samsung,exynos4")) {
>  		unsigned int tmp, core_id;
>  
>  		for (core_id = 0; core_id < num_possible_cpus(); core_id++) {

Maybe we need to change the compatible for exynos4415.dtsi? because no
exynos4 in the compatible...Applied, anyway.

Thanks,
Kukjin

[PATCH v3 2/2] ARM: EXYNOS: Use of_machine_is_compatible instead ofsoc_is_exynos4

[Kukjin Kim]

On 05/11/15 10:27, Krzysztof Kozlowski wrote:
> of_machine_is_compatible() seems to be preferred over soc_is_exynos4().
> 
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> 
> ---
> Changes since v2:
> 1. New patch, requested by Kukjin Kim.
> ---
>  arch/arm/mach-exynos/exynos.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
> index c3bfbba3006d..5917a30eee33 100644
> --- a/arch/arm/mach-exynos/exynos.c
> +++ b/arch/arm/mach-exynos/exynos.c
> @@ -179,7 +179,7 @@ static void __init exynos_init_io(void)
>   */
>  void exynos_set_delayed_reset_assertion(bool enable)
>  {
> -	if (soc_is_exynos4()) {
> +	if (of_machine_is_compatible("samsung,exynos4")) {
>  		unsigned int tmp, core_id;
>  
>  		for (core_id = 0; core_id < num_possible_cpus(); core_id++) {

Maybe we need to change the compatible for exynos4415.dtsi? because no
exynos4 in the compatible...Applied, anyway.

Thanks,
Kukjin

Re: [PATCH v3 2/2] ARM: EXYNOS: Use of_machine_is_compatible instead ofsoc_is_exynos4

[Krzysztof Kozlowski]

2015-05-14 11:41 GMT+09:00 Kukjin Kim <kgene@kernel.org>:
> On 05/11/15 10:27, Krzysztof Kozlowski wrote:
>> of_machine_is_compatible() seems to be preferred over soc_is_exynos4().
>>
>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>>
>> ---
>> Changes since v2:
>> 1. New patch, requested by Kukjin Kim.
>> ---
>>  arch/arm/mach-exynos/exynos.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
>> index c3bfbba3006d..5917a30eee33 100644
>> --- a/arch/arm/mach-exynos/exynos.c
>> +++ b/arch/arm/mach-exynos/exynos.c
>> @@ -179,7 +179,7 @@ static void __init exynos_init_io(void)
>>   */
>>  void exynos_set_delayed_reset_assertion(bool enable)
>>  {
>> -     if (soc_is_exynos4()) {
>> +     if (of_machine_is_compatible("samsung,exynos4")) {
>>               unsigned int tmp, core_id;
>>
>>               for (core_id = 0; core_id < num_possible_cpus(); core_id++) {
>
> Maybe we need to change the compatible for exynos4415.dtsi? because no
> exynos4 in the compatible...Applied, anyway.

It could be quite significant change and each path checking for
compatibility with exynos4 should be tested. There is no board DTS for
Exynos4415 so I am not quite convinced that we should care about it.

Best regards,
Krzysztof

[PATCH v3 2/2] ARM: EXYNOS: Use of_machine_is_compatible instead ofsoc_is_exynos4

[Krzysztof Kozlowski]

2015-05-14 11:41 GMT+09:00 Kukjin Kim <kgene@kernel.org>:
> On 05/11/15 10:27, Krzysztof Kozlowski wrote:
>> of_machine_is_compatible() seems to be preferred over soc_is_exynos4().
>>
>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>>
>> ---
>> Changes since v2:
>> 1. New patch, requested by Kukjin Kim.
>> ---
>>  arch/arm/mach-exynos/exynos.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
>> index c3bfbba3006d..5917a30eee33 100644
>> --- a/arch/arm/mach-exynos/exynos.c
>> +++ b/arch/arm/mach-exynos/exynos.c
>> @@ -179,7 +179,7 @@ static void __init exynos_init_io(void)
>>   */
>>  void exynos_set_delayed_reset_assertion(bool enable)
>>  {
>> -     if (soc_is_exynos4()) {
>> +     if (of_machine_is_compatible("samsung,exynos4")) {
>>               unsigned int tmp, core_id;
>>
>>               for (core_id = 0; core_id < num_possible_cpus(); core_id++) {
>
> Maybe we need to change the compatible for exynos4415.dtsi? because no
> exynos4 in the compatible...Applied, anyway.

It could be quite significant change and each path checking for
compatibility with exynos4 should be tested. There is no board DTS for
Exynos4415 so I am not quite convinced that we should care about it.

Best regards,
Krzysztof