[PATCH] arm: exynos: Support cluster power off on exynos5420/5800

[PATCH] arm: exynos: Support cluster power off on exynos5420/5800

[Abhilash Kesavan]

Turning off a cluster when all 4 cores of the cluster are powered off
saves power significantly. Powering off the A15 L2 alone gives around
100mW in savings. Add support for powering off the A15/A7 clusters on
exynos5420/5800.

The patch enables specific register bits which ensure that:
   - cluster L2 will be turned on before the first man is powered up.
   - last man will be turned off before the cluster L2 is turned off.
   - core is powered down before powering it up.

Remove the exynos_cluster_power_control function completely as we can
rely on the above mentioned bits rather than polling the cluster power
status register.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
---
The patch is based on Linux-next 20140618. It has been tested on an
exynos5420-based chromebook using the "/dev/bL_switcher" interface as
well as the script provided by Nicolas Pitre and Dave Martin [1].

Patch depends on:
[v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start

[1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html

 arch/arm/mach-exynos/mcpm-exynos.c | 66 ++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 35 deletions(-)

diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
index ace0ed6..95b5acf 100644
--- a/arch/arm/mach-exynos/mcpm-exynos.c
+++ b/arch/arm/mach-exynos/mcpm-exynos.c
@@ -26,6 +26,10 @@
 #define EXYNOS5420_CPUS_PER_CLUSTER	4
 #define EXYNOS5420_NR_CLUSTERS		2
 
+#define EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN	BIT(9)
+#define EXYNOS5420_USE_ARM_CORE_DOWN_STATE	BIT(29)
+#define EXYNOS5420_USE_L2_COMMON_UP_STATE	BIT(30)
+
 /*
  * The common v7_exit_coherency_flush API could not be used because of the
  * Erratum 799270 workaround. This macro is the same as the common one (in
@@ -73,36 +77,9 @@ cpu_use_count[EXYNOS5420_CPUS_PER_CLUSTER][EXYNOS5420_NR_CLUSTERS];
 
 #define exynos_cluster_unused(cluster) !exynos_cluster_usecnt(cluster)
 
-static int exynos_cluster_power_control(unsigned int cluster, int enable)
-{
-	unsigned int tries = 100;
-	unsigned int val;
-
-	if (enable) {
-		exynos_cluster_power_up(cluster);
-		val = S5P_CORE_LOCAL_PWR_EN;
-	} else {
-		exynos_cluster_power_down(cluster);
-		val = 0;
-	}
-
-	/* Wait until cluster power control is applied */
-	while (tries--) {
-		if (exynos_cluster_power_state(cluster) == val)
-			return 0;
-
-		cpu_relax();
-	}
-	pr_debug("timed out waiting for cluster %u to power %s\n", cluster,
-		enable ? "on" : "off");
-
-	return -ETIMEDOUT;
-}
-
 static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 {
 	unsigned int cpunr = cpu + (cluster * EXYNOS5420_CPUS_PER_CLUSTER);
-	int err = 0;
 
 	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
 	if (cpu >= EXYNOS5420_CPUS_PER_CLUSTER ||
@@ -126,12 +103,9 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 		 * cores.
 		 */
 		if (was_cluster_down)
-			err = exynos_cluster_power_control(cluster, 1);
+			exynos_cluster_power_up(cluster);
 
-		if (!err)
-			exynos_cpu_power_up(cpunr);
-		else
-			exynos_cluster_power_control(cluster, 0);
+		exynos_cpu_power_up(cpunr);
 	} else if (cpu_use_count[cpu][cluster] != 2) {
 		/*
 		 * The only possible values are:
@@ -147,7 +121,7 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 	arch_spin_unlock(&exynos_mcpm_lock);
 	local_irq_enable();
 
-	return err;
+	return 0;
 }
 
 /*
@@ -178,9 +152,10 @@ static void exynos_power_down(void)
 	if (cpu_use_count[cpu][cluster] == 0) {
 		exynos_cpu_power_down(cpunr);
 
-		if (exynos_cluster_unused(cluster))
-			/* TODO: Turn off the cluster here to save power. */
+		if (exynos_cluster_unused(cluster)) {
+			exynos_cluster_power_down(cluster);
 			last_man = true;
+		}
 	} else if (cpu_use_count[cpu][cluster] == 1) {
 		/*
 		 * A power_up request went ahead of us.
@@ -299,6 +274,7 @@ static int __init exynos_mcpm_init(void)
 {
 	struct device_node *node;
 	void __iomem *ns_sram_base_addr;
+	unsigned int value, i;
 	int ret;
 
 	node = of_find_matching_node(NULL, exynos_dt_mcpm_match);
@@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
 	pr_info("Exynos MCPM support installed\n");
 
 	/*
+	 * On Exynos5420/5800 for the A15 and A7 clusters:
+	 *
+	 * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
+	 * in a cluster are turned off before turning off the cluster L2.
+	 *
+	 * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
+	 * off before waking it up.
+	 *
+	 * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
+	 * turned on before the first man is powered up.
+	 */
+	for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
+		value = __raw_readl(EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
+		value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
+			 EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
+			 EXYNOS5420_USE_L2_COMMON_UP_STATE;
+		__raw_writel(value, EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
+	}
+
+	/*
 	 * U-Boot SPL is hardcoded to jump to the start of ns_sram_base_addr
 	 * as part of secondary_cpu_start().  Let's redirect it to the
 	 * mcpm_entry_point().
-- 
2.0.0

[PATCH] arm: exynos: Support cluster power off on exynos5420/5800

[Abhilash Kesavan]

Turning off a cluster when all 4 cores of the cluster are powered off
saves power significantly. Powering off the A15 L2 alone gives around
100mW in savings. Add support for powering off the A15/A7 clusters on
exynos5420/5800.

The patch enables specific register bits which ensure that:
   - cluster L2 will be turned on before the first man is powered up.
   - last man will be turned off before the cluster L2 is turned off.
   - core is powered down before powering it up.

Remove the exynos_cluster_power_control function completely as we can
rely on the above mentioned bits rather than polling the cluster power
status register.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
---
The patch is based on Linux-next 20140618. It has been tested on an
exynos5420-based chromebook using the "/dev/bL_switcher" interface as
well as the script provided by Nicolas Pitre and Dave Martin [1].

Patch depends on:
[v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start

[1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html

 arch/arm/mach-exynos/mcpm-exynos.c | 66 ++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 35 deletions(-)

diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
index ace0ed6..95b5acf 100644
--- a/arch/arm/mach-exynos/mcpm-exynos.c
+++ b/arch/arm/mach-exynos/mcpm-exynos.c
@@ -26,6 +26,10 @@
 #define EXYNOS5420_CPUS_PER_CLUSTER	4
 #define EXYNOS5420_NR_CLUSTERS		2
 
+#define EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN	BIT(9)
+#define EXYNOS5420_USE_ARM_CORE_DOWN_STATE	BIT(29)
+#define EXYNOS5420_USE_L2_COMMON_UP_STATE	BIT(30)
+
 /*
  * The common v7_exit_coherency_flush API could not be used because of the
  * Erratum 799270 workaround. This macro is the same as the common one (in
@@ -73,36 +77,9 @@ cpu_use_count[EXYNOS5420_CPUS_PER_CLUSTER][EXYNOS5420_NR_CLUSTERS];
 
 #define exynos_cluster_unused(cluster) !exynos_cluster_usecnt(cluster)
 
-static int exynos_cluster_power_control(unsigned int cluster, int enable)
-{
-	unsigned int tries = 100;
-	unsigned int val;
-
-	if (enable) {
-		exynos_cluster_power_up(cluster);
-		val = S5P_CORE_LOCAL_PWR_EN;
-	} else {
-		exynos_cluster_power_down(cluster);
-		val = 0;
-	}
-
-	/* Wait until cluster power control is applied */
-	while (tries--) {
-		if (exynos_cluster_power_state(cluster) == val)
-			return 0;
-
-		cpu_relax();
-	}
-	pr_debug("timed out waiting for cluster %u to power %s\n", cluster,
-		enable ? "on" : "off");
-
-	return -ETIMEDOUT;
-}
-
 static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 {
 	unsigned int cpunr = cpu + (cluster * EXYNOS5420_CPUS_PER_CLUSTER);
-	int err = 0;
 
 	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
 	if (cpu >= EXYNOS5420_CPUS_PER_CLUSTER ||
@@ -126,12 +103,9 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 		 * cores.
 		 */
 		if (was_cluster_down)
-			err = exynos_cluster_power_control(cluster, 1);
+			exynos_cluster_power_up(cluster);
 
-		if (!err)
-			exynos_cpu_power_up(cpunr);
-		else
-			exynos_cluster_power_control(cluster, 0);
+		exynos_cpu_power_up(cpunr);
 	} else if (cpu_use_count[cpu][cluster] != 2) {
 		/*
 		 * The only possible values are:
@@ -147,7 +121,7 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 	arch_spin_unlock(&exynos_mcpm_lock);
 	local_irq_enable();
 
-	return err;
+	return 0;
 }
 
 /*
@@ -178,9 +152,10 @@ static void exynos_power_down(void)
 	if (cpu_use_count[cpu][cluster] == 0) {
 		exynos_cpu_power_down(cpunr);
 
-		if (exynos_cluster_unused(cluster))
-			/* TODO: Turn off the cluster here to save power. */
+		if (exynos_cluster_unused(cluster)) {
+			exynos_cluster_power_down(cluster);
 			last_man = true;
+		}
 	} else if (cpu_use_count[cpu][cluster] == 1) {
 		/*
 		 * A power_up request went ahead of us.
@@ -299,6 +274,7 @@ static int __init exynos_mcpm_init(void)
 {
 	struct device_node *node;
 	void __iomem *ns_sram_base_addr;
+	unsigned int value, i;
 	int ret;
 
 	node = of_find_matching_node(NULL, exynos_dt_mcpm_match);
@@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
 	pr_info("Exynos MCPM support installed\n");
 
 	/*
+	 * On Exynos5420/5800 for the A15 and A7 clusters:
+	 *
+	 * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
+	 * in a cluster are turned off before turning off the cluster L2.
+	 *
+	 * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
+	 * off before waking it up.
+	 *
+	 * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
+	 * turned on before the first man is powered up.
+	 */
+	for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
+		value = __raw_readl(EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
+		value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
+			 EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
+			 EXYNOS5420_USE_L2_COMMON_UP_STATE;
+		__raw_writel(value, EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
+	}
+
+	/*
 	 * U-Boot SPL is hardcoded to jump to the start of ns_sram_base_addr
 	 * as part of secondary_cpu_start().  Let's redirect it to the
 	 * mcpm_entry_point().
-- 
2.0.0

Re: [PATCH] arm: exynos: Support cluster power off on exynos5420/5800

[Nicolas Pitre]

On Wed, 18 Jun 2014, Abhilash Kesavan wrote:

> Turning off a cluster when all 4 cores of the cluster are powered off
> saves power significantly. Powering off the A15 L2 alone gives around
> 100mW in savings. Add support for powering off the A15/A7 clusters on
> exynos5420/5800.
> 
> The patch enables specific register bits which ensure that:
>    - cluster L2 will be turned on before the first man is powered up.
>    - last man will be turned off before the cluster L2 is turned off.
>    - core is powered down before powering it up.
> 
> Remove the exynos_cluster_power_control function completely as we can
> rely on the above mentioned bits rather than polling the cluster power
> status register.
> 
> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>

Minor nit below:

> @@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
>  	pr_info("Exynos MCPM support installed\n");
>  
>  	/*
> +	 * On Exynos5420/5800 for the A15 and A7 clusters:
> +	 *
> +	 * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
> +	 * in a cluster are turned off before turning off the cluster L2.
> +	 *
> +	 * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
> +	 * off before waking it up.
> +	 *
> +	 * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
> +	 * turned on before the first man is powered up.
> +	 */
> +	for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
> +		value = __raw_readl(EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
> +		value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
> +			 EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
> +			 EXYNOS5420_USE_L2_COMMON_UP_STATE;
> +		__raw_writel(value, EXYNOS_COMMON_CONFIGURATION(i) + 0x8);

Surely you can add another define in mach-exynos/regs-pmu.h to better 
identify this register instead of EXYNOS_COMMON_CONFIGURATION()+8 ?

After that, you may add:

Acked-by: Nicolas Pitre <nico@linaro.org>


Nicolas

[PATCH] arm: exynos: Support cluster power off on exynos5420/5800

[Nicolas Pitre]

On Wed, 18 Jun 2014, Abhilash Kesavan wrote:

> Turning off a cluster when all 4 cores of the cluster are powered off
> saves power significantly. Powering off the A15 L2 alone gives around
> 100mW in savings. Add support for powering off the A15/A7 clusters on
> exynos5420/5800.
> 
> The patch enables specific register bits which ensure that:
>    - cluster L2 will be turned on before the first man is powered up.
>    - last man will be turned off before the cluster L2 is turned off.
>    - core is powered down before powering it up.
> 
> Remove the exynos_cluster_power_control function completely as we can
> rely on the above mentioned bits rather than polling the cluster power
> status register.
> 
> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>

Minor nit below:

> @@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
>  	pr_info("Exynos MCPM support installed\n");
>  
>  	/*
> +	 * On Exynos5420/5800 for the A15 and A7 clusters:
> +	 *
> +	 * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
> +	 * in a cluster are turned off before turning off the cluster L2.
> +	 *
> +	 * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
> +	 * off before waking it up.
> +	 *
> +	 * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
> +	 * turned on before the first man is powered up.
> +	 */
> +	for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
> +		value = __raw_readl(EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
> +		value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
> +			 EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
> +			 EXYNOS5420_USE_L2_COMMON_UP_STATE;
> +		__raw_writel(value, EXYNOS_COMMON_CONFIGURATION(i) + 0x8);

Surely you can add another define in mach-exynos/regs-pmu.h to better 
identify this register instead of EXYNOS_COMMON_CONFIGURATION()+8 ?

After that, you may add:

Acked-by: Nicolas Pitre <nico@linaro.org>


Nicolas

Re: [PATCH] arm: exynos: Support cluster power off on exynos5420/5800

[Abhilash Kesavan]

Hi Nicolas,

On Wed, Jun 18, 2014 at 9:10 PM, Nicolas Pitre <nicolas.pitre@linaro.org> wrote:
> On Wed, 18 Jun 2014, Abhilash Kesavan wrote:
>
>> Turning off a cluster when all 4 cores of the cluster are powered off
>> saves power significantly. Powering off the A15 L2 alone gives around
>> 100mW in savings. Add support for powering off the A15/A7 clusters on
>> exynos5420/5800.
>>
>> The patch enables specific register bits which ensure that:
>>    - cluster L2 will be turned on before the first man is powered up.
>>    - last man will be turned off before the cluster L2 is turned off.
>>    - core is powered down before powering it up.
>>
>> Remove the exynos_cluster_power_control function completely as we can
>> rely on the above mentioned bits rather than polling the cluster power
>> status register.
>>
>> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
>
> Minor nit below:
>
>> @@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
>>       pr_info("Exynos MCPM support installed\n");
>>
>>       /*
>> +      * On Exynos5420/5800 for the A15 and A7 clusters:
>> +      *
>> +      * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
>> +      * in a cluster are turned off before turning off the cluster L2.
>> +      *
>> +      * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
>> +      * off before waking it up.
>> +      *
>> +      * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
>> +      * turned on before the first man is powered up.
>> +      */
>> +     for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
>> +             value = __raw_readl(EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
>> +             value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
>> +                      EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
>> +                      EXYNOS5420_USE_L2_COMMON_UP_STATE;
>> +             __raw_writel(value, EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
>
> Surely you can add another define in mach-exynos/regs-pmu.h to better
> identify this register instead of EXYNOS_COMMON_CONFIGURATION()+8 ?
>
> After that, you may add:
>
> Acked-by: Nicolas Pitre <nico@linaro.org>
Thanks. Will fix and post v2 with your ack.

Regards,
Abhilash
>
>
> Nicolas

[PATCH] arm: exynos: Support cluster power off on exynos5420/5800

[Abhilash Kesavan]

Hi Nicolas,

On Wed, Jun 18, 2014 at 9:10 PM, Nicolas Pitre <nicolas.pitre@linaro.org> wrote:
> On Wed, 18 Jun 2014, Abhilash Kesavan wrote:
>
>> Turning off a cluster when all 4 cores of the cluster are powered off
>> saves power significantly. Powering off the A15 L2 alone gives around
>> 100mW in savings. Add support for powering off the A15/A7 clusters on
>> exynos5420/5800.
>>
>> The patch enables specific register bits which ensure that:
>>    - cluster L2 will be turned on before the first man is powered up.
>>    - last man will be turned off before the cluster L2 is turned off.
>>    - core is powered down before powering it up.
>>
>> Remove the exynos_cluster_power_control function completely as we can
>> rely on the above mentioned bits rather than polling the cluster power
>> status register.
>>
>> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
>
> Minor nit below:
>
>> @@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
>>       pr_info("Exynos MCPM support installed\n");
>>
>>       /*
>> +      * On Exynos5420/5800 for the A15 and A7 clusters:
>> +      *
>> +      * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
>> +      * in a cluster are turned off before turning off the cluster L2.
>> +      *
>> +      * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
>> +      * off before waking it up.
>> +      *
>> +      * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
>> +      * turned on before the first man is powered up.
>> +      */
>> +     for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
>> +             value = __raw_readl(EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
>> +             value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
>> +                      EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
>> +                      EXYNOS5420_USE_L2_COMMON_UP_STATE;
>> +             __raw_writel(value, EXYNOS_COMMON_CONFIGURATION(i) + 0x8);
>
> Surely you can add another define in mach-exynos/regs-pmu.h to better
> identify this register instead of EXYNOS_COMMON_CONFIGURATION()+8 ?
>
> After that, you may add:
>
> Acked-by: Nicolas Pitre <nico@linaro.org>
Thanks. Will fix and post v2 with your ack.

Regards,
Abhilash
>
>
> Nicolas

[PATCH v2] arm: exynos: Support cluster power off on exynos5420/5800

[Abhilash Kesavan]

Turning off a cluster when all 4 cores of the cluster are powered off
saves power significantly. Powering off the A15 L2 alone gives around
100mW in savings. Add support for powering off the A15/A7 clusters on
exynos5420/5800.

The patch enables specific register bits which ensure that:
   - cluster L2 will be turned on before the first man is powered up.
   - last man will be turned off before the cluster L2 is turned off.
   - core is powered down before powering it up.

Remove the exynos_cluster_power_control function completely as we can
rely on the above mentioned bits rather than polling the cluster power
status register.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
---
Change in v2:
Added a macro for the COMMON_OPTION register and used it in the MCPM
back-end.

The patch is based on Linux-next 20140619. It has been tested on an
exynos5420-based chromebook using the "/dev/bL_switcher" interface as
well as the script provided by Nicolas Pitre and Dave Martin [1].

Patch depends on:
[v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start

[1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html

 arch/arm/mach-exynos/mcpm-exynos.c |   66 +++++++++++++++++-------------------
 arch/arm/mach-exynos/regs-pmu.h    |    2 ++
 2 files changed, 33 insertions(+), 35 deletions(-)

diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
index ace0ed6..619cbc6 100644
--- a/arch/arm/mach-exynos/mcpm-exynos.c
+++ b/arch/arm/mach-exynos/mcpm-exynos.c
@@ -26,6 +26,10 @@
 #define EXYNOS5420_CPUS_PER_CLUSTER	4
 #define EXYNOS5420_NR_CLUSTERS		2
 
+#define EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN	BIT(9)
+#define EXYNOS5420_USE_ARM_CORE_DOWN_STATE	BIT(29)
+#define EXYNOS5420_USE_L2_COMMON_UP_STATE	BIT(30)
+
 /*
  * The common v7_exit_coherency_flush API could not be used because of the
  * Erratum 799270 workaround. This macro is the same as the common one (in
@@ -73,36 +77,9 @@ cpu_use_count[EXYNOS5420_CPUS_PER_CLUSTER][EXYNOS5420_NR_CLUSTERS];
 
 #define exynos_cluster_unused(cluster) !exynos_cluster_usecnt(cluster)
 
-static int exynos_cluster_power_control(unsigned int cluster, int enable)
-{
-	unsigned int tries = 100;
-	unsigned int val;
-
-	if (enable) {
-		exynos_cluster_power_up(cluster);
-		val = S5P_CORE_LOCAL_PWR_EN;
-	} else {
-		exynos_cluster_power_down(cluster);
-		val = 0;
-	}
-
-	/* Wait until cluster power control is applied */
-	while (tries--) {
-		if (exynos_cluster_power_state(cluster) == val)
-			return 0;
-
-		cpu_relax();
-	}
-	pr_debug("timed out waiting for cluster %u to power %s\n", cluster,
-		enable ? "on" : "off");
-
-	return -ETIMEDOUT;
-}
-
 static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 {
 	unsigned int cpunr = cpu + (cluster * EXYNOS5420_CPUS_PER_CLUSTER);
-	int err = 0;
 
 	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
 	if (cpu >= EXYNOS5420_CPUS_PER_CLUSTER ||
@@ -126,12 +103,9 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 		 * cores.
 		 */
 		if (was_cluster_down)
-			err = exynos_cluster_power_control(cluster, 1);
+			exynos_cluster_power_up(cluster);
 
-		if (!err)
-			exynos_cpu_power_up(cpunr);
-		else
-			exynos_cluster_power_control(cluster, 0);
+		exynos_cpu_power_up(cpunr);
 	} else if (cpu_use_count[cpu][cluster] != 2) {
 		/*
 		 * The only possible values are:
@@ -147,7 +121,7 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 	arch_spin_unlock(&exynos_mcpm_lock);
 	local_irq_enable();
 
-	return err;
+	return 0;
 }
 
 /*
@@ -178,9 +152,10 @@ static void exynos_power_down(void)
 	if (cpu_use_count[cpu][cluster] == 0) {
 		exynos_cpu_power_down(cpunr);
 
-		if (exynos_cluster_unused(cluster))
-			/* TODO: Turn off the cluster here to save power. */
+		if (exynos_cluster_unused(cluster)) {
+			exynos_cluster_power_down(cluster);
 			last_man = true;
+		}
 	} else if (cpu_use_count[cpu][cluster] == 1) {
 		/*
 		 * A power_up request went ahead of us.
@@ -299,6 +274,7 @@ static int __init exynos_mcpm_init(void)
 {
 	struct device_node *node;
 	void __iomem *ns_sram_base_addr;
+	unsigned int value, i;
 	int ret;
 
 	node = of_find_matching_node(NULL, exynos_dt_mcpm_match);
@@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
 	pr_info("Exynos MCPM support installed\n");
 
 	/*
+	 * On Exynos5420/5800 for the A15 and A7 clusters:
+	 *
+	 * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
+	 * in a cluster are turned off before turning off the cluster L2.
+	 *
+	 * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
+	 * off before waking it up.
+	 *
+	 * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
+	 * turned on before the first man is powered up.
+	 */
+	for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
+		value = __raw_readl(EXYNOS_COMMON_OPTION(i));
+		value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
+			 EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
+			 EXYNOS5420_USE_L2_COMMON_UP_STATE;
+		__raw_writel(value, EXYNOS_COMMON_OPTION(i));
+	}
+
+	/*
 	 * U-Boot SPL is hardcoded to jump to the start of ns_sram_base_addr
 	 * as part of secondary_cpu_start().  Let's redirect it to the
 	 * mcpm_entry_point().
diff --git a/arch/arm/mach-exynos/regs-pmu.h b/arch/arm/mach-exynos/regs-pmu.h
index 1d13b08..bda8df0 100644
--- a/arch/arm/mach-exynos/regs-pmu.h
+++ b/arch/arm/mach-exynos/regs-pmu.h
@@ -117,6 +117,8 @@
 			(EXYNOS_ARM_COMMON_CONFIGURATION + (0x80 * (_nr)))
 #define EXYNOS_COMMON_STATUS(_nr)		\
 			(EXYNOS_COMMON_CONFIGURATION(_nr) + 0x4)
+#define EXYNOS_COMMON_OPTION(_nr)		\
+			(EXYNOS_COMMON_CONFIGURATION(_nr) + 0x8)
 
 #define S5P_PAD_RET_MAUDIO_OPTION		S5P_PMUREG(0x3028)
 #define S5P_PAD_RET_GPIO_OPTION			S5P_PMUREG(0x3108)
-- 
1.7.9.5

[PATCH v2] arm: exynos: Support cluster power off on exynos5420/5800

[Abhilash Kesavan]

Turning off a cluster when all 4 cores of the cluster are powered off
saves power significantly. Powering off the A15 L2 alone gives around
100mW in savings. Add support for powering off the A15/A7 clusters on
exynos5420/5800.

The patch enables specific register bits which ensure that:
   - cluster L2 will be turned on before the first man is powered up.
   - last man will be turned off before the cluster L2 is turned off.
   - core is powered down before powering it up.

Remove the exynos_cluster_power_control function completely as we can
rely on the above mentioned bits rather than polling the cluster power
status register.

Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
---
Change in v2:
Added a macro for the COMMON_OPTION register and used it in the MCPM
back-end.

The patch is based on Linux-next 20140619. It has been tested on an
exynos5420-based chromebook using the "/dev/bL_switcher" interface as
well as the script provided by Nicolas Pitre and Dave Martin [1].

Patch depends on:
[v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start

[1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html

 arch/arm/mach-exynos/mcpm-exynos.c |   66 +++++++++++++++++-------------------
 arch/arm/mach-exynos/regs-pmu.h    |    2 ++
 2 files changed, 33 insertions(+), 35 deletions(-)

diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
index ace0ed6..619cbc6 100644
--- a/arch/arm/mach-exynos/mcpm-exynos.c
+++ b/arch/arm/mach-exynos/mcpm-exynos.c
@@ -26,6 +26,10 @@
 #define EXYNOS5420_CPUS_PER_CLUSTER	4
 #define EXYNOS5420_NR_CLUSTERS		2
 
+#define EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN	BIT(9)
+#define EXYNOS5420_USE_ARM_CORE_DOWN_STATE	BIT(29)
+#define EXYNOS5420_USE_L2_COMMON_UP_STATE	BIT(30)
+
 /*
  * The common v7_exit_coherency_flush API could not be used because of the
  * Erratum 799270 workaround. This macro is the same as the common one (in
@@ -73,36 +77,9 @@ cpu_use_count[EXYNOS5420_CPUS_PER_CLUSTER][EXYNOS5420_NR_CLUSTERS];
 
 #define exynos_cluster_unused(cluster) !exynos_cluster_usecnt(cluster)
 
-static int exynos_cluster_power_control(unsigned int cluster, int enable)
-{
-	unsigned int tries = 100;
-	unsigned int val;
-
-	if (enable) {
-		exynos_cluster_power_up(cluster);
-		val = S5P_CORE_LOCAL_PWR_EN;
-	} else {
-		exynos_cluster_power_down(cluster);
-		val = 0;
-	}
-
-	/* Wait until cluster power control is applied */
-	while (tries--) {
-		if (exynos_cluster_power_state(cluster) == val)
-			return 0;
-
-		cpu_relax();
-	}
-	pr_debug("timed out waiting for cluster %u to power %s\n", cluster,
-		enable ? "on" : "off");
-
-	return -ETIMEDOUT;
-}
-
 static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 {
 	unsigned int cpunr = cpu + (cluster * EXYNOS5420_CPUS_PER_CLUSTER);
-	int err = 0;
 
 	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
 	if (cpu >= EXYNOS5420_CPUS_PER_CLUSTER ||
@@ -126,12 +103,9 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 		 * cores.
 		 */
 		if (was_cluster_down)
-			err = exynos_cluster_power_control(cluster, 1);
+			exynos_cluster_power_up(cluster);
 
-		if (!err)
-			exynos_cpu_power_up(cpunr);
-		else
-			exynos_cluster_power_control(cluster, 0);
+		exynos_cpu_power_up(cpunr);
 	} else if (cpu_use_count[cpu][cluster] != 2) {
 		/*
 		 * The only possible values are:
@@ -147,7 +121,7 @@ static int exynos_power_up(unsigned int cpu, unsigned int cluster)
 	arch_spin_unlock(&exynos_mcpm_lock);
 	local_irq_enable();
 
-	return err;
+	return 0;
 }
 
 /*
@@ -178,9 +152,10 @@ static void exynos_power_down(void)
 	if (cpu_use_count[cpu][cluster] == 0) {
 		exynos_cpu_power_down(cpunr);
 
-		if (exynos_cluster_unused(cluster))
-			/* TODO: Turn off the cluster here to save power. */
+		if (exynos_cluster_unused(cluster)) {
+			exynos_cluster_power_down(cluster);
 			last_man = true;
+		}
 	} else if (cpu_use_count[cpu][cluster] == 1) {
 		/*
 		 * A power_up request went ahead of us.
@@ -299,6 +274,7 @@ static int __init exynos_mcpm_init(void)
 {
 	struct device_node *node;
 	void __iomem *ns_sram_base_addr;
+	unsigned int value, i;
 	int ret;
 
 	node = of_find_matching_node(NULL, exynos_dt_mcpm_match);
@@ -342,6 +318,26 @@ static int __init exynos_mcpm_init(void)
 	pr_info("Exynos MCPM support installed\n");
 
 	/*
+	 * On Exynos5420/5800 for the A15 and A7 clusters:
+	 *
+	 * EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN ensures that all the cores
+	 * in a cluster are turned off before turning off the cluster L2.
+	 *
+	 * EXYNOS5420_USE_ARM_CORE_DOWN_STATE ensures that a cores is powered
+	 * off before waking it up.
+	 *
+	 * EXYNOS5420_USE_L2_COMMON_UP_STATE ensures that cluster L2 will be
+	 * turned on before the first man is powered up.
+	 */
+	for (i = 0; i < EXYNOS5420_NR_CLUSTERS; i++) {
+		value = __raw_readl(EXYNOS_COMMON_OPTION(i));
+		value |= EXYNOS5420_ENABLE_AUTOMATIC_CORE_DOWN |
+			 EXYNOS5420_USE_ARM_CORE_DOWN_STATE    |
+			 EXYNOS5420_USE_L2_COMMON_UP_STATE;
+		__raw_writel(value, EXYNOS_COMMON_OPTION(i));
+	}
+
+	/*
 	 * U-Boot SPL is hardcoded to jump to the start of ns_sram_base_addr
 	 * as part of secondary_cpu_start().  Let's redirect it to the
 	 * mcpm_entry_point().
diff --git a/arch/arm/mach-exynos/regs-pmu.h b/arch/arm/mach-exynos/regs-pmu.h
index 1d13b08..bda8df0 100644
--- a/arch/arm/mach-exynos/regs-pmu.h
+++ b/arch/arm/mach-exynos/regs-pmu.h
@@ -117,6 +117,8 @@
 			(EXYNOS_ARM_COMMON_CONFIGURATION + (0x80 * (_nr)))
 #define EXYNOS_COMMON_STATUS(_nr)		\
 			(EXYNOS_COMMON_CONFIGURATION(_nr) + 0x4)
+#define EXYNOS_COMMON_OPTION(_nr)		\
+			(EXYNOS_COMMON_CONFIGURATION(_nr) + 0x8)
 
 #define S5P_PAD_RET_MAUDIO_OPTION		S5P_PMUREG(0x3028)
 #define S5P_PAD_RET_GPIO_OPTION			S5P_PMUREG(0x3108)
-- 
1.7.9.5

Re: [PATCH v2] arm: exynos: Support cluster power off on exynos5420/5800

[Kevin Hilman]

Abhilash Kesavan <a.kesavan@samsung.com> writes:

> Turning off a cluster when all 4 cores of the cluster are powered off
> saves power significantly. Powering off the A15 L2 alone gives around
> 100mW in savings. Add support for powering off the A15/A7 clusters on
> exynos5420/5800.
>
> The patch enables specific register bits which ensure that:
>    - cluster L2 will be turned on before the first man is powered up.
>    - last man will be turned off before the cluster L2 is turned off.
>    - core is powered down before powering it up.
>
> Remove the exynos_cluster_power_control function completely as we can
> rely on the above mentioned bits rather than polling the cluster power
> status register.
>
> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
> Acked-by: Nicolas Pitre <nico@linaro.org>
> ---
> Change in v2:
> Added a macro for the COMMON_OPTION register and used it in the MCPM
> back-end.
>
> The patch is based on Linux-next 20140619. It has been tested on an
> exynos5420-based chromebook using the "/dev/bL_switcher" interface as
> well as the script provided by Nicolas Pitre and Dave Martin [1].
>
> Patch depends on:
> [v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
>
> [1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html

Tested on exynos5800/Chromebook2 along with the dependency patch and using
the script from Dave and Nico.

Tested-by: Kevin Hilman <khilman@linaro.org>

Kevin

[PATCH v2] arm: exynos: Support cluster power off on exynos5420/5800

[Kevin Hilman]

Abhilash Kesavan <a.kesavan@samsung.com> writes:

> Turning off a cluster when all 4 cores of the cluster are powered off
> saves power significantly. Powering off the A15 L2 alone gives around
> 100mW in savings. Add support for powering off the A15/A7 clusters on
> exynos5420/5800.
>
> The patch enables specific register bits which ensure that:
>    - cluster L2 will be turned on before the first man is powered up.
>    - last man will be turned off before the cluster L2 is turned off.
>    - core is powered down before powering it up.
>
> Remove the exynos_cluster_power_control function completely as we can
> rely on the above mentioned bits rather than polling the cluster power
> status register.
>
> Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
> Acked-by: Nicolas Pitre <nico@linaro.org>
> ---
> Change in v2:
> Added a macro for the COMMON_OPTION register and used it in the MCPM
> back-end.
>
> The patch is based on Linux-next 20140619. It has been tested on an
> exynos5420-based chromebook using the "/dev/bL_switcher" interface as
> well as the script provided by Nicolas Pitre and Dave Martin [1].
>
> Patch depends on:
> [v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
>
> [1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html

Tested on exynos5800/Chromebook2 along with the dependency patch and using
the script from Dave and Nico.

Tested-by: Kevin Hilman <khilman@linaro.org>

Kevin

RE: [PATCH v2] arm: exynos: Support cluster power off on exynos5420/5800

[Kukjin Kim]

Kevin Hilman wrote:
> 
> Abhilash Kesavan <a.kesavan@samsung.com> writes:
> 
Hi,

> > Turning off a cluster when all 4 cores of the cluster are powered off
> > saves power significantly. Powering off the A15 L2 alone gives around
> > 100mW in savings. Add support for powering off the A15/A7 clusters on
> > exynos5420/5800.
> >
> > The patch enables specific register bits which ensure that:
> >    - cluster L2 will be turned on before the first man is powered up.
> >    - last man will be turned off before the cluster L2 is turned off.
> >    - core is powered down before powering it up.
> >
> > Remove the exynos_cluster_power_control function completely as we can
> > rely on the above mentioned bits rather than polling the cluster power
> > status register.
> >
> > Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
> > Acked-by: Nicolas Pitre <nico@linaro.org>
> > ---
> > Change in v2:
> > Added a macro for the COMMON_OPTION register and used it in the MCPM
> > back-end.
> >
> > The patch is based on Linux-next 20140619. It has been tested on an
> > exynos5420-based chromebook using the "/dev/bL_switcher" interface as
> > well as the script provided by Nicolas Pitre and Dave Martin [1].
> >
> > Patch depends on:
> > [v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
> >
> > [1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html
> 
> Tested on exynos5800/Chromebook2 along with the dependency patch and using
> the script from Dave and Nico.
> 
> Tested-by: Kevin Hilman <khilman@linaro.org>
> 
Kevin, thanks for your test on the board ;-)

Applied into samsung tree.

Thanks,
Kukjin

[PATCH v2] arm: exynos: Support cluster power off on exynos5420/5800

[Kukjin Kim]

Kevin Hilman wrote:
> 
> Abhilash Kesavan <a.kesavan@samsung.com> writes:
> 
Hi,

> > Turning off a cluster when all 4 cores of the cluster are powered off
> > saves power significantly. Powering off the A15 L2 alone gives around
> > 100mW in savings. Add support for powering off the A15/A7 clusters on
> > exynos5420/5800.
> >
> > The patch enables specific register bits which ensure that:
> >    - cluster L2 will be turned on before the first man is powered up.
> >    - last man will be turned off before the cluster L2 is turned off.
> >    - core is powered down before powering it up.
> >
> > Remove the exynos_cluster_power_control function completely as we can
> > rely on the above mentioned bits rather than polling the cluster power
> > status register.
> >
> > Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
> > Acked-by: Nicolas Pitre <nico@linaro.org>
> > ---
> > Change in v2:
> > Added a macro for the COMMON_OPTION register and used it in the MCPM
> > back-end.
> >
> > The patch is based on Linux-next 20140619. It has been tested on an
> > exynos5420-based chromebook using the "/dev/bL_switcher" interface as
> > well as the script provided by Nicolas Pitre and Dave Martin [1].
> >
> > Patch depends on:
> > [v2] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start
> >
> > [1] http://www.spinics.net/lists/linux-samsung-soc/msg31257.html
> 
> Tested on exynos5800/Chromebook2 along with the dependency patch and using
> the script from Dave and Nico.
> 
> Tested-by: Kevin Hilman <khilman@linaro.org>
> 
Kevin, thanks for your test on the board ;-)

Applied into samsung tree.

Thanks,
Kukjin