[PATCH v4 5/5] arm: exynos: Add MCPM call-back functions
Nicolas Pitre
nicolas.pitre at linaro.org
Fri May 2 11:16:11 PDT 2014
On Fri, 2 May 2014, Abhilash Kesavan wrote:
> Add machine-dependent MCPM call-backs for Exynos5420. These are used
> to power up/down the secondary CPUs during boot, shutdown, s2r and
> switching.
>
> Signed-off-by: Thomas Abraham <thomas.ab at samsung.com>
> Signed-off-by: Inderpal Singh <inderpal.s at samsung.com>
> Signed-off-by: Andrew Bresticker <abrestic at chromium.org>
> Signed-off-by: Abhilash Kesavan <a.kesavan at samsung.com>
OK.... There is still a detail wrong. At least we are converging.
> ---
> arch/arm/mach-exynos/Kconfig | 8 +
> arch/arm/mach-exynos/Makefile | 2 +
> arch/arm/mach-exynos/mcpm-exynos.c | 345 ++++++++++++++++++++++++++++++++++++
> arch/arm/mach-exynos/regs-pmu.h | 3 +
> 4 files changed, 358 insertions(+)
> create mode 100644 arch/arm/mach-exynos/mcpm-exynos.c
>
> diff --git a/arch/arm/mach-exynos/Kconfig b/arch/arm/mach-exynos/Kconfig
> index 5c34dc2..138070e 100644
> --- a/arch/arm/mach-exynos/Kconfig
> +++ b/arch/arm/mach-exynos/Kconfig
> @@ -73,4 +73,12 @@ config SOC_EXYNOS5440
>
> endmenu
>
> +config EXYNOS5420_MCPM
> + bool "Exynos5420 Multi-Cluster PM support"
> + depends on MCPM && SOC_EXYNOS5420
> + select ARM_CCI
> + help
> + This is needed to provide CPU and cluster power management
> + on Exynos5420 implementing big.LITTLE.
> +
> endif
> diff --git a/arch/arm/mach-exynos/Makefile b/arch/arm/mach-exynos/Makefile
> index a656dbe..01bc9b9 100644
> --- a/arch/arm/mach-exynos/Makefile
> +++ b/arch/arm/mach-exynos/Makefile
> @@ -29,3 +29,5 @@ obj-$(CONFIG_ARCH_EXYNOS) += firmware.o
>
> plus_sec := $(call as-instr,.arch_extension sec,+sec)
> AFLAGS_exynos-smc.o :=-Wa,-march=armv7-a$(plus_sec)
> +
> +obj-$(CONFIG_EXYNOS5420_MCPM) += mcpm-exynos.o
> diff --git a/arch/arm/mach-exynos/mcpm-exynos.c b/arch/arm/mach-exynos/mcpm-exynos.c
> new file mode 100644
> index 0000000..d0f7461
> --- /dev/null
> +++ b/arch/arm/mach-exynos/mcpm-exynos.c
> @@ -0,0 +1,345 @@
> +/*
> + * Copyright (c) 2014 Samsung Electronics Co., Ltd.
> + * http://www.samsung.com
> + *
> + * arch/arm/mach-exynos/mcpm-exynos.c
> + *
> + * Based on arch/arm/mach-vexpress/dcscb.c
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/arm-cci.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +
> +#include <asm/cputype.h>
> +#include <asm/cp15.h>
> +#include <asm/mcpm.h>
> +
> +#include "regs-pmu.h"
> +#include "common.h"
> +
> +#define EXYNOS5420_CPUS_PER_CLUSTER 4
> +#define EXYNOS5420_NR_CLUSTERS 2
> +
> +/* Non-secure iRAM base address */
> +static void __iomem *ns_sram_base_addr;
> +
> +/*
> + * 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
> + * arch/arm/include/asm/cacheflush.h) except for the erratum handling.
> + */
> +#define exynos_v7_exit_coherency_flush(level) \
> + asm volatile( \
> + "stmfd sp!, {fp, ip}\n\t"\
> + "mrc p15, 0, r0, c1, c0, 0 @ get SCTLR\n\t" \
> + "bic r0, r0, #"__stringify(CR_C)"\n\t" \
> + "mcr p15, 0, r0, c1, c0, 0 @ set SCTLR\n\t" \
> + "isb\n\t"\
> + "bl v7_flush_dcache_"__stringify(level)"\n\t" \
> + "clrex\n\t"\
> + "mrc p15, 0, r0, c1, c0, 1 @ get ACTLR\n\t" \
> + "bic r0, r0, #(1 << 6) @ disable local coherency\n\t" \
> + /* Dummy Load of a device register to avoid Erratum 799270 */ \
> + "ldr r4, [%0]\n\t" \
> + "and r4, r4, #0\n\t" \
> + "orr r0, r0, r4\n\t" \
> + "mcr p15, 0, r0, c1, c0, 1 @ set ACTLR\n\t" \
> + "isb\n\t" \
> + "dsb\n\t" \
> + "ldmfd sp!, {fp, ip}" \
> + : \
> + : "Ir" (S5P_INFORM0) \
> + : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", \
> + "r9", "r10", "lr", "memory")
> +
> +/*
> + * We can't use regular spinlocks. In the switcher case, it is possible
> + * for an outbound CPU to call power_down() after its inbound counterpart
> + * is already live using the same logical CPU number which trips lockdep
> + * debugging.
> + */
> +static arch_spinlock_t exynos_mcpm_lock = __ARCH_SPIN_LOCK_UNLOCKED;
> +static int
> +cpu_use_count[EXYNOS5420_CPUS_PER_CLUSTER][EXYNOS5420_NR_CLUSTERS];
> +
> +#define exynos_cluster_unused(cluster) \
> + (!cpu_use_count[0][cluster] && \
> + !cpu_use_count[1][cluster] && \
> + !cpu_use_count[2][cluster] && \
> + !cpu_use_count[3][cluster])
> +
> +static int exynos_cluster_power_control(unsigned int cluster, int enable)
> +{
> + unsigned int tries = 100;
> + unsigned int val;
> +
> + if (enable) {
> + exynos_cluster_powerup(cluster);
> + val = S5P_CORE_LOCAL_PWR_EN;
> + } else {
> + exynos_cluster_powerdown(cluster);
> + val = 0;
> + }
> +
> + /* Wait until cluster power control is applied */
> + while (tries--) {
> + if (exynos_cluster_power_state(cluster) == val)
> + return 0;
> +
> + cpu_relax();
> + }
> + pr_warn("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 ||
> + cluster >= EXYNOS5420_NR_CLUSTERS)
> + return -EINVAL;
> +
> + /*
> + * Since this is called with IRQs enabled, and no arch_spin_lock_irq
> + * variant exists, we need to disable IRQs manually here.
> + */
> + local_irq_disable();
> + arch_spin_lock(&exynos_mcpm_lock);
> +
> + cpu_use_count[cpu][cluster]++;
> + if (cpu_use_count[cpu][cluster] == 1) {
> + bool was_cluster_down =
> + __mcpm_cluster_state(cluster) == CLUSTER_DOWN;
This is racy. I probably made this comment already. The MCPM cluster
state may change in mcpm-head.S where concurrency protection is achieved
with a different mechanism.
What you should do instead is to redefine exynos_cluster_unused() into
exynos_cluster_usecnt() and simply add all counts together. You could
even have:
#define exynos_cluster_unused(cluster) !exynos_cluster_usecnt(cluster)
Yet, here you should use:
bool was_cluster_down = (exynos_cluster_usecnt(cluster) == 1);
> +
> + /*
> + * Turn on the cluster (L2/COMMON) and then power on the
> + * cores.
> + */
> + if (was_cluster_down)
> + err = exynos_cluster_power_control(cluster, 1);
> +
> + if (!err)
> + exynos_cpu_powerup(cpunr);
> + else
> + exynos_cluster_power_control(cluster, 0);
> + } else if (cpu_use_count[cpu][cluster] != 2) {
> + /*
> + * The only possible values are:
> + * 0 = CPU down
> + * 1 = CPU (still) up
> + * 2 = CPU requested to be up before it had a chance
> + * to actually make itself down.
> + * Any other value is a bug.
> + */
> + BUG();
> + }
> +
> + arch_spin_unlock(&exynos_mcpm_lock);
> + local_irq_enable();
> +
> + return err;
> +}
> +
> +static void exynos_power_down(void)
> +{
> + unsigned int mpidr, cpu, cluster;
> + bool last_man = false, skip_wfi = false;
> + unsigned int cpunr;
> +
> + mpidr = read_cpuid_mpidr();
> + cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
> + cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
> + cpunr = cpu + (cluster * EXYNOS5420_CPUS_PER_CLUSTER);
> +
> + pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
> + BUG_ON(cpu >= EXYNOS5420_CPUS_PER_CLUSTER ||
> + cluster >= EXYNOS5420_NR_CLUSTERS);
> +
> + __mcpm_cpu_going_down(cpu, cluster);
> +
> + arch_spin_lock(&exynos_mcpm_lock);
> + BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
> + cpu_use_count[cpu][cluster]--;
> + if (cpu_use_count[cpu][cluster] == 0) {
> + exynos_cpu_powerdown(cpunr);
> +
> + if (exynos_cluster_unused(cluster))
> + last_man = true;
> + } else if (cpu_use_count[cpu][cluster] == 1) {
> + /*
> + * A power_up request went ahead of us.
> + * Even if we do not want to shut this CPU down,
> + * the caller expects a certain state as if the WFI
> + * was aborted. So let's continue with cache cleaning.
> + */
> + skip_wfi = true;
> + } else {
> + BUG();
> + }
> +
> + /*
> + * TODO: Turn off the clusters when all cores in the cluster
> + * are down to achieve significant power savings.
> + */
This comment should actually be located right after the
"if (exynos_cluster_unused(cluster))" above. That is where the cluster
control should be applied, assuming it'll be effective only when WFI is
executed.
> + if (last_man && __mcpm_outbound_enter_critical(cpu, cluster)) {
> + arch_spin_unlock(&exynos_mcpm_lock);
> +
> + /* Flush all cache levels for this cluster. */
> + exynos_v7_exit_coherency_flush(all);
> +
> + /*
> + * Disable cluster-level coherency by masking
> + * incoming snoops and DVM messages:
> + */
> + cci_disable_port_by_cpu(mpidr);
> +
> + __mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
> + } else {
> + arch_spin_unlock(&exynos_mcpm_lock);
> +
> + if (read_cpuid_part_number() == ARM_CPU_PART_CORTEX_A15) {
> + /*
> + * On the Cortex-A15 we need to disable
> + * L2 prefetching before flushing the cache.
> + */
> + asm volatile(
> + "mcr p15, 1, %0, c15, c0, 3\n\t"
> + "isb\n\t"
> + "dsb"
> + : : "r" (0x400));
> + }
This doesn't belong here. That is for the last_man only to do, right
before the "Flush all cache levels for this cluster" comment.
The rest looks fine to me.
Nicolas
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