Re: [PATCH 2/2] cpuidle: exynos: add coupled cpuidle support for Exynos4210

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 11/07/2014 07:00 PM, Bartlomiej Zolnierkiewicz wrote:
> The following patch adds coupled cpuidle support for Exynos4210 to
> an existing cpuidle-exynos driver.  As a result it enables AFTR mode
> to be used by default on Exynos4210 without the need to hot unplug
> CPU1 first.
>
> The patch is heavily based on earlier cpuidle-exynos4210 driver from
> Daniel Lezcano:
>
> http://www.spinics.net/lists/linux-samsung-soc/msg28134.html
>
> Changes from Daniel's code include:
> - porting code to current kernels
> - fixing it to work on my setup (by using S5P_INFORM register
>    instead of S5P_VA_SYSRAM one on Revison 1.1 and retrying poking
>    CPU1 out of the BOOT ROM if necessary)
> - fixing rare lockup caused by waiting for CPU1 to get stuck in
>    the BOOT ROM (CPU hotplug code in arch/arm/mach-exynos/platsmp.c
>    doesn't require this and works fine)
> - moving Exynos specific code to arch/arm/mach-exynos/pm.c
> - using cpu_boot_reg_base() helper instead of BOOT_VECTOR macro
> - using exynos_cpu_*() helpers instead of accessing registers
>    directly
> - using arch_send_wakeup_ipi_mask() instead of dsb_sev()
>    (this matches CPU hotplug code in arch/arm/mach-exynos/platsmp.c)

I am curious. You experienced very rare hangs after running the tests a 
few hours, right ? Is the SEV replaced by the IPI solving the issue ? If 
yes, how did you catch it ?

>- integrating separate exynos4210-cpuidle driver into existing
>    exynos-cpuidle one
>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Colin Cross <ccross@google.com>
> Cc: Kukjin Kim <kgene.kim@samsung.com>
> Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Cc: Tomasz Figa <tomasz.figa@gmail.com>
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

A few comments below:

> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
>   arch/arm/mach-exynos/common.h                |   4 +
>   arch/arm/mach-exynos/exynos.c                |   4 +
>   arch/arm/mach-exynos/platsmp.c               |   2 +-
>   arch/arm/mach-exynos/pm.c                    | 122 +++++++++++++++++++++++++++
>   drivers/cpuidle/Kconfig.arm                  |   1 +
>   drivers/cpuidle/cpuidle-exynos.c             |  62 ++++++++++++--
>   include/linux/platform_data/cpuidle-exynos.h |  20 +++++
>   7 files changed, 209 insertions(+), 6 deletions(-)
>   create mode 100644 include/linux/platform_data/cpuidle-exynos.h
>
> diff --git a/arch/arm/mach-exynos/common.h b/arch/arm/mach-exynos/common.h
> index d4d09bc..f208a60 100644
> --- a/arch/arm/mach-exynos/common.h
> +++ b/arch/arm/mach-exynos/common.h
> @@ -14,6 +14,7 @@
>
>   #include <linux/reboot.h>
>   #include <linux/of.h>
> +#include <linux/platform_data/cpuidle-exynos.h>
>
>   #define EXYNOS3250_SOC_ID	0xE3472000
>   #define EXYNOS3_SOC_MASK	0xFFFFF000
> @@ -168,8 +169,11 @@ extern void exynos_pm_central_suspend(void);
>   extern int exynos_pm_central_resume(void);
>   extern void exynos_enter_aftr(void);
>
> +extern struct cpuidle_exynos_data cpuidle_coupled_exynos_data;
> +
>   extern void s5p_init_cpu(void __iomem *cpuid_addr);
>   extern unsigned int samsung_rev(void);
> +extern void __iomem *cpu_boot_reg_base(void);
>
>   static inline void pmu_raw_writel(u32 val, u32 offset)
>   {
> diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
> index a487e59..4f4eb9e 100644
> --- a/arch/arm/mach-exynos/exynos.c
> +++ b/arch/arm/mach-exynos/exynos.c
> @@ -317,6 +317,10 @@ static void __init exynos_dt_machine_init(void)
>   	if (!IS_ENABLED(CONFIG_SMP))
>   		exynos_sysram_init();
>
> +#ifdef CONFIG_ARM_EXYNOS_CPUIDLE
> +	if (of_machine_is_compatible("samsung,exynos4210"))
> +		exynos_cpuidle.dev.platform_data = &cpuidle_coupled_exynos_data;
> +#endif

You should not add those #ifdef.

>   	if (of_machine_is_compatible("samsung,exynos4210") ||
>   	    of_machine_is_compatible("samsung,exynos4212") ||
>   	    (of_machine_is_compatible("samsung,exynos4412") &&
> diff --git a/arch/arm/mach-exynos/platsmp.c b/arch/arm/mach-exynos/platsmp.c
> index adb36a8..0e3ffc9 100644
> --- a/arch/arm/mach-exynos/platsmp.c
> +++ b/arch/arm/mach-exynos/platsmp.c
> @@ -182,7 +182,7 @@ int exynos_cluster_power_state(int cluster)
>   		S5P_CORE_LOCAL_PWR_EN);
>   }
>
> -static inline void __iomem *cpu_boot_reg_base(void)
> +void __iomem *cpu_boot_reg_base(void)
>   {
>   	if (soc_is_exynos4210() && samsung_rev() == EXYNOS4210_REV_1_1)
>   		return pmu_base_addr + S5P_INFORM5;
> diff --git a/arch/arm/mach-exynos/pm.c b/arch/arm/mach-exynos/pm.c
> index 4b36ab5..44cc08a 100644
> --- a/arch/arm/mach-exynos/pm.c
> +++ b/arch/arm/mach-exynos/pm.c
> @@ -178,3 +178,125 @@ void exynos_enter_aftr(void)
>
>   	cpu_pm_exit();
>   }
> +
> +static atomic_t cpu1_wakeup = ATOMIC_INIT(0);
> +
> +static int exynos_cpu0_enter_aftr(void)
> +{
> +	int ret = -1;
> +
> +	/*
> +	 * If the other cpu is powered on, we have to power it off, because
> +	 * the AFTR state won't work otherwise
> +	 */
> +	if (cpu_online(1)) {
> +		/*
> +		 * We reach a sync point with the coupled idle state, we know
> +		 * the other cpu will power down itself or will abort the
> +		 * sequence, let's wait for one of these to happen
> +		 */
> +		while (exynos_cpu_power_state(1)) {
> +			/*
> +			 * The other cpu may skip idle and boot back
> +			 * up again
> +			 */
> +			if (atomic_read(&cpu1_wakeup))
> +				goto abort;
> +
> +			/*
> +			 * The other cpu may bounce through idle and
> +			 * boot back up again, getting stuck in the
> +			 * boot rom code
> +			 */
> +			if (__raw_readl(cpu_boot_reg_base()) == 0)
> +				goto abort;
> +
> +			cpu_relax();
> +		}
> +	}
> +
> +	exynos_enter_aftr();
> +	ret = 0;
> +
> +abort:
> +	if (cpu_online(1)) {
> +		/*
> +		 * Set the boot vector to something non-zero
> +		 */
> +		__raw_writel(virt_to_phys(exynos_cpu_resume),
> +			     cpu_boot_reg_base());
> +		dsb();
> +
> +		/*
> +		 * Turn on cpu1 and wait for it to be on
> +		 */
> +		exynos_cpu_power_up(1);
> +		while (exynos_cpu_power_state(1) != S5P_CORE_LOCAL_PWR_EN)
> +			cpu_relax();
> +
> +		while (!atomic_read(&cpu1_wakeup)) {
> +			/*
> +			 * Poke cpu1 out of the boot rom
> +			 */
> +			__raw_writel(virt_to_phys(exynos_cpu_resume),
> +				     cpu_boot_reg_base());
> +
> +			arch_send_wakeup_ipi_mask(cpumask_of(1));
> +		}
> +	}
> +
> +	return ret;
> +}
> +
> +static int exynos_wfi_finisher(unsigned long flags)
> +{
> +	cpu_do_idle();
> +
> +	return -1;
> +}
> +
> +static int exynos_cpu1_powerdown(void)
> +{
> +	int ret = -1;
> +
> +	/*
> +	 * Idle sequence for cpu1
> +	 */
> +	if (cpu_pm_enter())
> +		goto cpu1_aborted;
> +
> +	/*
> +	 * Turn off cpu 1
> +	 */
> +	exynos_cpu_power_down(1);
> +
> +	ret = cpu_suspend(0, exynos_wfi_finisher);
> +
> +	cpu_pm_exit();
> +
> +cpu1_aborted:
> +	dsb();
> +	/*
> +	 * Notify cpu 0 that cpu 1 is awake
> +	 */
> +	atomic_set(&cpu1_wakeup, 1);
> +
> +	return ret;
> +}
> +
> +static void exynos_pre_enter_aftr(void)
> +{
> +	__raw_writel(virt_to_phys(exynos_cpu_resume), cpu_boot_reg_base());
> +}
> +
> +static void exynos_post_enter_aftr(void)
> +{
> +	atomic_set(&cpu1_wakeup, 0);
> +}
> +
> +struct cpuidle_exynos_data cpuidle_coupled_exynos_data = {
> +	.cpu0_enter_aftr		= exynos_cpu0_enter_aftr,
> +	.cpu1_powerdown		= exynos_cpu1_powerdown,
> +	.pre_enter_aftr		= exynos_pre_enter_aftr,
> +	.post_enter_aftr		= exynos_post_enter_aftr,
> +};
> diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
> index 8c16ab2..8e07c94 100644
> --- a/drivers/cpuidle/Kconfig.arm
> +++ b/drivers/cpuidle/Kconfig.arm
> @@ -55,6 +55,7 @@ config ARM_AT91_CPUIDLE
>   config ARM_EXYNOS_CPUIDLE
>   	bool "Cpu Idle Driver for the Exynos processors"
>   	depends on ARCH_EXYNOS
> +	select ARCH_NEEDS_CPU_IDLE_COUPLED if SMP
>   	help
>   	  Select this to enable cpuidle for Exynos processors
>
> diff --git a/drivers/cpuidle/cpuidle-exynos.c b/drivers/cpuidle/cpuidle-exynos.c
> index ba9b34b..4700d5d 100644
> --- a/drivers/cpuidle/cpuidle-exynos.c
> +++ b/drivers/cpuidle/cpuidle-exynos.c
> @@ -1,8 +1,11 @@
> -/* linux/arch/arm/mach-exynos/cpuidle.c
> - *
> - * Copyright (c) 2011 Samsung Electronics Co., Ltd.
> +/*
> + * Copyright (c) 2011-2014 Samsung Electronics Co., Ltd.
>    *		http://www.samsung.com
>    *
> + * Coupled cpuidle support based on the work of:
> + *	Colin Cross <ccross@android.com>
> + *	Daniel Lezcano <daniel.lezcano@linaro.org>
> + *
>    * 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.
> @@ -13,13 +16,49 @@
>   #include <linux/export.h>
>   #include <linux/module.h>
>   #include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/platform_data/cpuidle-exynos.h>
>
>   #include <asm/proc-fns.h>
>   #include <asm/suspend.h>
>   #include <asm/cpuidle.h>
>
> +static atomic_t exynos_idle_barrier;
> +
> +static struct cpuidle_exynos_data *exynos_cpuidle_pdata;
>   static void (*exynos_enter_aftr)(void);
>
> +static int exynos_enter_coupled_lowpower(struct cpuidle_device *dev,
> +					 struct cpuidle_driver *drv,
> +					 int index)
> +{
> +	int ret;
> +
> +	exynos_cpuidle_pdata->pre_enter_aftr();
> +
> +	/*
> +	 * Waiting all cpus to reach this point at the same moment
> +	 */
> +	cpuidle_coupled_parallel_barrier(dev, &exynos_idle_barrier);
> +
> +	/*
> +	 * Both cpus will reach this point at the same time
> +	 */
> +	ret = dev->cpu ? exynos_cpuidle_pdata->cpu1_powerdown()
> +		       : exynos_cpuidle_pdata->cpu0_enter_aftr();
> +	if (ret)
> +		index = ret;
> +
> +	/*
> +	 * Waiting all cpus to finish the power sequence before going further
> +	 */
> +	cpuidle_coupled_parallel_barrier(dev, &exynos_idle_barrier);
> +
> +	exynos_cpuidle_pdata->post_enter_aftr();
> +
> +	return index;
> +}
> +
>   static int exynos_enter_lowpower(struct cpuidle_device *dev,
>   				struct cpuidle_driver *drv,
>   				int index)
> @@ -58,11 +97,24 @@ static struct cpuidle_driver exynos_idle_driver = {
>
>   static int exynos_cpuidle_probe(struct platform_device *pdev)
>   {
> +	const struct cpumask *coupled_cpus = NULL;
>   	int ret;
>
> -	exynos_enter_aftr = (void *)(pdev->dev.platform_data);
> +	if (of_machine_is_compatible("samsung,exynos4210")) {
> +		exynos_cpuidle_pdata = pdev->dev.platform_data;
> +
> +		exynos_idle_driver.states[1].enter =
> +						exynos_enter_coupled_lowpower;
> +		exynos_idle_driver.states[1].exit_latency = 5000;
> +		exynos_idle_driver.states[1].target_residency = 10000;
> +		exynos_idle_driver.states[1].flags |= CPUIDLE_FLAG_COUPLED |
> +						      CPUIDLE_FLAG_TIMER_STOP;

I tried to remove those dynamic state allocation everywhere in the 
different drivers. I would prefer to have another cpuidle_driver to be 
registered with its states instead of overwriting the existing idle state.

struct cpuidle_driver exynos4210_idle_driver = {
	.name = "exynos4210_idle",
	.owner = THIS_MODULE,
	.states = {
		[0] = ARM_CPUIDLE_WFI_STATE,
                 [1] = {
                         .enter = exynos_enter_coupled_lowpower,
                         .exit_latency = 5000,
                         .target_residency = 10000,
			.flags = CPUIDLE_FLAG_TIME_VALID |
				CPUIDLE_FLAG_COUPLED |
				CPUIDLE_FLAG_TIMER_STOP,
                         .name = "C1",
                         .desc = "ARM power down",
                 },
	}
};


and then:

if (of_machine_is_compatible("samsung,exynos4210")) {
	...
	ret = cpuidle_register(&exynos4210_idle_driver,
				cpu_online_mask);
	...
}
...

If we can reuse this mechanism, which I believe it is possible to, for 
4420 and 5250. Then we will be able to refactor this out again.

> +
> +		coupled_cpus = cpu_possible_mask;
> +	} else
> +		exynos_enter_aftr = (void *)(pdev->dev.platform_data);
>
> -	ret = cpuidle_register(&exynos_idle_driver, NULL);
> +	ret = cpuidle_register(&exynos_idle_driver, coupled_cpus);
>   	if (ret) {
>   		dev_err(&pdev->dev, "failed to register cpuidle driver\n");
>   		return ret;
> diff --git a/include/linux/platform_data/cpuidle-exynos.h b/include/linux/platform_data/cpuidle-exynos.h
> new file mode 100644
> index 0000000..bfa40e4
> --- /dev/null
> +++ b/include/linux/platform_data/cpuidle-exynos.h
> @@ -0,0 +1,20 @@
> +/*
> + * Copyright (c) 2014 Samsung Electronics Co., Ltd.
> + *              http://www.samsung.com
> + *
> + * 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.
> +*/
> +
> +#ifndef __CPUIDLE_EXYNOS_H
> +#define __CPUIDLE_EXYNOS_H
> +
> +struct cpuidle_exynos_data {
> +	int (*cpu0_enter_aftr)(void);
> +	int (*cpu1_powerdown)(void);
> +	void (*pre_enter_aftr)(void);
> +	void (*post_enter_aftr)(void);
> +};
> +
> +#endif
>


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