| Message ID | 1403104722-14848-1-git-send-email-a.kesavan@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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
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
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().
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(-)