ARM: EXYNOS: Support cluster power off on exynos5420/5800

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>
Tested-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
index 13a2108..9315ba9 100644 (file)
--- 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.
@@ -335,6 +310,7 @@ 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);
@@ -377,6 +353,26 @@ 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

diff --git a/arch/arm/mach-exynos/regs-pmu.h b/arch/arm/mach-exynos/regs-pmu.h
index c45a2dc..e5e298c 100644 (file)
--- a/arch/arm/mach-exynos/regs-pmu.h
+++ b/arch/arm/mach-exynos/regs-pmu.h
@@ -116,6 +116,8 @@
                        (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)