[PATCH v2] arm: exynos: Support cluster power off on exynos5420/5800
Abhilash Kesavan
a.kesavan at samsung.com
Thu Jun 19 05:40:17 PDT 2014
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 at samsung.com>
Acked-by: Nicolas Pitre <nico at 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
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