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>

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 13a210865c6f..9315ba91c1fb 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.
@@ -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);
@@ -378,6 +354,26 @@ 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 c45a2dc53e84..e5e298c0fd01 100644
--- 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)