Re: [PATCH v4 5/5] arm: exynos: Add MCPM call-back functions

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




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@xxxxxxxxxxx>
> Signed-off-by: Inderpal Singh <inderpal.s@xxxxxxxxxxx>
> Signed-off-by: Andrew Bresticker <abrestic@xxxxxxxxxxxx>
> Signed-off-by: Abhilash Kesavan <a.kesavan@xxxxxxxxxxx>

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
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]
  Powered by Linux