Subject: [PATCH] Exynos4: cpuidle: support dual CPUs with AFTR state

From: [email-masked] (Lukasz Majewski)
Date: Wed, 16 Apr 2014 00:19:41 +0200

On Tue, 15 Apr 2014 18:38:39 +0200
Daniel Lezcano <[email-masked]> wrote:

> 
> On 04/15/2014 05:54 PM, Lukasz Majewski wrote:
> > Hi Daniel,
> >
> >> On 04/15/2014 08:37 AM, Lukasz Majewski wrote:
> >>> Hi Daniel,
> >>>
> >>>> The following driver is for exynos4210. I did not yet finished
> >>>> the other boards, so I created a specific driver for 4210 which
> >>>> could be merged later.
> >>>>
> >>>
> >>> If I may ask - do you plan to develop this code for Exynos4412 in
> >>> a near future?
> >>
> >> Yes it is in my plan.
> >>
> >>> I did some tests (with hotplug) and it turns out, that due to
> >>> static leakage current one can save up to 12 % of power
> >>> consumption when power domains for cores are disabled.
> >>>
> >>>
> >>> Such notable power consumption reduction could drive (and justify)
> >>> the further development of power aware scheduling code.
> >>>
> >>> If you don't have time, then I can offer myself to develop the
> >>> code. I just want to avoid potential duplication of effort.
> >>
> >> I would be very glad if we can cooperate. Thanks for proposing your
> >> help.
> >
> > You are welcome :-)
> >
> >>
> >> I have put a branch containing the cleanups + driver moving + dual
> >> cpu support, so you can base your work in it.
> >>
> >> git://git.linaro.org/people/daniel.lezcano/linux.git
> >> cpuidle/samsung-next
> >
> > Thanks for sharing code. I will look into it.
> >
> >>
> >> I am wondering if the 5250 board wouldn't make sense as a primary
> >> target before the 4412...
> >
> > I'm working on a device based on 4412, not 5250. Therefore, I would
> > prefer to have this concept implemented on 4412 as soon as possible
> > to not hinder my scheduler related experiments.
> >
> > If you have other priorities, then we can split the work. What do
> > you think?
> 
> It is ok for me if you want to handle the cpuidle driver 4412.

Ok. Thanks :-)

> Will
> you create a new driver or extend this dual cpu driver to support 4
> cpus ?

For the beginning, I will try to extend the solution proposed for
Exynos4210. 

However, because of the Easter break, the code will be delivered at
next week.

> 
> 
> >>>> The driver is based on Colin Cross's driver found at:
> >>>>
> >>>> https://android.googlesource.com/kernel/exynos/+/e686b1ec67423c40b4fdf811f9a4dfa3b393a010%5E%5E!/
> >>>>
> >>>> This one was based on a 3.4 kernel and an old API.
> >>>>
> >>>> It has been refreshed, simplified and based on the recent code
> >>>> cleanup I sent today.
> >>>>
> >>>> The AFTR could be entered when all the cpus (except cpu0) are
> >>>> down. In order to reach this situation, the couple idle states
> >>>> are used.
> >>>>
> >>>> There is a sync barrier at the entry and the exit of the low
> >>>> power function. So all cpus will enter and exit the function at
> >>>> the same time.
> >>>>
> >>>> At this point, CPU0 knows the other cpu will power down itself.
> >>>> CPU0 waits for the CPU1 to be powered down and then initiate the
> >>>> AFTR power down sequence.
> >>>>
> >>>> No interrupts are handled by CPU1, this is why we switch to the
> >>>> timer broadcast even if the local timer is not impacted by the
> >>>> idle state.
> >>>>
> >>>> When CPU0 wakes up, it powers up CPU1 and waits for it to boot.
> >>>> Then they both exit the idle function.
> >>>>
> >>>> This driver allows the exynos4210 to have the same power
> >>>> consumption at idle time than the one when we have to unplug CPU1
> >>>> in order to let CPU0 to reach the AFTR state.
> >>>>
> >>>> This patch is a RFC because, we have to find a way to remove the
> >>>> macros definitions and cpu powerdown function without pulling the
> >>>> arch dependent headers.
> >>>>
> >>>> Signed-off-by: Daniel Lezcano <[email-masked]>
> >>>> ---
> >>>>    arch/arm/mach-exynos/common.c        |   11 +-
> >>>>    drivers/cpuidle/Kconfig.arm          |    8 ++
> >>>>    drivers/cpuidle/Makefile             |    1 +
> >>>>    drivers/cpuidle/cpuidle-exynos4210.c |  226
> >>>> ++++++++++++++++++++++++++++++++++ 4 files changed, 245
> >>>> insertions(+), 1 deletion(-) create mode 100644
> >>>> drivers/cpuidle/cpuidle-exynos4210.c
> >>>>
> >>>> diff --git a/arch/arm/mach-exynos/common.c
> >>>> b/arch/arm/mach-exynos/common.c index d5fa21e..1765a98 100644
> >>>> --- a/arch/arm/mach-exynos/common.c
> >>>> +++ b/arch/arm/mach-exynos/common.c
> >>>> @@ -299,9 +299,18 @@ static struct platform_device exynos_cpuidle
> >>>> = { .id                = -1,
> >>>>    };
> >>>>
> >>>> +static struct platform_device exynos4210_cpuidle = {
> >>>> +       .name              = "exynos4210-cpuidle",
> >>>> +       .dev.platform_data = exynos_sys_powerdown_aftr,
> >>>> +       .id                = -1,
> >>>> +};
> >>>> +
> >>>>    void __init exynos_cpuidle_init(void)
> >>>>    {
> >>>> -       platform_device_register(&exynos_cpuidle);
> >>>> +       if (soc_is_exynos4210())
> >>>> +               platform_device_register(&exynos4210_cpuidle);
> >>>> +       else
> >>>> +               platform_device_register(&exynos_cpuidle);
> >>>>    }
> >>>>
> >>>>    void __init exynos_cpufreq_init(void)
> >>>> diff --git a/drivers/cpuidle/Kconfig.arm
> >>>> b/drivers/cpuidle/Kconfig.arm index 92f0c12..2772130 100644
> >>>> --- a/drivers/cpuidle/Kconfig.arm
> >>>> +++ b/drivers/cpuidle/Kconfig.arm
> >>>> @@ -51,3 +51,11 @@ config ARM_EXYNOS_CPUIDLE
> >>>>           depends on ARCH_EXYNOS
> >>>>           help
> >>>>             Select this to enable cpuidle for Exynos processors
> >>>> +
> >>>> +config ARM_EXYNOS4210_CPUIDLE
> >>>> +       bool "Cpu Idle Driver for the Exynos 4210 processor"
> >>>> +       default y
> >>>> +       depends on ARCH_EXYNOS
> >>>> +       select ARCH_NEEDS_CPU_IDLE_COUPLED if SMP
> >>>> +       help
> >>>> +         Select this to enable cpuidle for the Exynos 4210
> >>>> processors diff --git a/drivers/cpuidle/Makefile
> >>>> b/drivers/cpuidle/Makefile index 0d1540a..e0ec9bc 100644
> >>>> --- a/drivers/cpuidle/Makefile
> >>>> +++ b/drivers/cpuidle/Makefile
> >>>> @@ -14,6 +14,7 @@ obj-$(CONFIG_ARM_ZYNQ_CPUIDLE)
> >>>> += cpuidle-zynq.o obj-$(CONFIG_ARM_U8500_CPUIDLE)         +=
> >>>> cpuidle-ux500.o obj-$(CONFIG_ARM_AT91_CPUIDLE)          +=
> >>>> cpuidle-at91.o obj-$(CONFIG_ARM_EXYNOS_CPUIDLE)        +=
> >>>> cpuidle-exynos.o +obj-$(CONFIG_ARM_EXYNOS4210_CPUIDLE)    +=
> >>>> cpuidle-exynos4210.o
> >>>>
> >>>>    ###############################################################################
> >>>>    # POWERPC drivers
> >>>> diff --git a/drivers/cpuidle/cpuidle-exynos4210.c
> >>>> b/drivers/cpuidle/cpuidle-exynos4210.c new file mode 100644
> >>>> index 0000000..56f6d51
> >>>> --- /dev/null
> >>>> +++ b/drivers/cpuidle/cpuidle-exynos4210.c
> >>>> @@ -0,0 +1,226 @@
> >>>> +/*
> >>>> + * Copyright (c) 2014 Samsung Electronics Co., Ltd.
> >>>> + *             http://www.samsung.com
> >>>> + *
> >>>> + * Copyright (c) 2014 Linaro : Daniel Lezcano
> >>>> <[email-masked]>
> >>>> + *             http://www.linaro.org
> >>>> + *
> >>>> + * Based on the work of Colin Cross <[email-masked]>
> >>>> + *
> >>>> + * 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/cpuidle.h>
> >>>> +#include <linux/cpu_pm.h>
> >>>> +#include <linux/io.h>
> >>>> +#include <linux/platform_device.h>
> >>>> +
> >>>> +#include <asm/proc-fns.h>
> >>>> +#include <asm/suspend.h>
> >>>> +#include <asm/cpuidle.h>
> >>>> +
> >>>> +#include <plat/pm.h>
> >>>> +#include <plat/cpu.h>
> >>>> +#include <plat/map-base.h>
> >>>> +#include <plat/map-s5p.h>
> >>>> +
> >>>> +static atomic_t exynos_idle_barrier;
> >>>> +static atomic_t cpu1_wakeup = ATOMIC_INIT(0);
> >>>> +
> >>>> +#define BOOT_VECTOR S5P_VA_SYSRAM
> >>>> +#define S5P_VA_PMU                  S3C_ADDR(0x02180000)
> >>>> +#define S5P_PMUREG(x)              (S5P_VA_PMU + (x))
> >>>> +#define S5P_ARM_CORE1_CONFIGURATION S5P_PMUREG(0x2080)
> >>>> +#define S5P_ARM_CORE1_STATUS        S5P_PMUREG(0x2084)
> >>>> +
> >>>> +static void (*exynos_aftr)(void);
> >>>> +
> >>>> +static int cpu_suspend_finish(unsigned long flags)
> >>>> +{
> >>>> +       if (flags)
> >>>> +               exynos_aftr();
> >>>> +
> >>>> +       cpu_do_idle();
> >>>> +
> >>>> +       return -1;
> >>>> +}
> >>>> +
> >>>> +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 (__raw_readl(S5P_ARM_CORE1_STATUS) & 3) {
> >>>> +
> >>>> +                       /*
> >>>> +                        * 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(BOOT_VECTOR) == 0)
> >>>> +                               goto abort;
> >>>> +
> >>>> +                       cpu_relax();
> >>>> +               }
> >>>> +       }
> >>>> +
> >>>> +       cpu_pm_enter();
> >>>> +
> >>>> +       ret = cpu_suspend(1, cpu_suspend_finish);
> >>>> +
> >>>> +       cpu_pm_exit();
> >>>> +
> >>>> +abort:
> >>>> +       if (cpu_online(1)) {
> >>>> +               /*
> >>>> +                * Set the boot vector to something non-zero
> >>>> +                */
> >>>> +               __raw_writel(virt_to_phys(s3c_cpu_resume),
> >>>> +                            BOOT_VECTOR);
> >>>> +               dsb();
> >>>> +
> >>>> +               /*
> >>>> +                * Turn on cpu1 and wait for it to be on
> >>>> +                */
> >>>> +               __raw_writel(0x3, S5P_ARM_CORE1_CONFIGURATION);
> >>>> +               while ((__raw_readl(S5P_ARM_CORE1_STATUS) & 3) !=
> >>>> 3)
> >>>> +                       cpu_relax();
> >>>> +
> >>>> +               /*
> >>>> +                * Wait for cpu1 to get stuck in the boot rom
> >>>> +                */
> >>>> +               while ((__raw_readl(BOOT_VECTOR) != 0) &&
> >>>> +                      !atomic_read(&cpu1_wakeup))
> >>>> +                       cpu_relax();
> >>>> +
> >>>> +               if (!atomic_read(&cpu1_wakeup)) {
> >>>> +                       /*
> >>>> +                        * Poke cpu1 out of the boot rom
> >>>> +                        */
> >>>> +
> >>>> __raw_writel(virt_to_phys(s3c_cpu_resume),
> >>>> +                                    BOOT_VECTOR);
> >>>> +                       dsb_sev();
> >>>> +               }
> >>>> +
> >>>> +               /*
> >>>> +                * Wait for cpu1 to finish booting
> >>>> +                */
> >>>> +               while (!atomic_read(&cpu1_wakeup))
> >>>> +                       cpu_relax();
> >>>> +       }
> >>>> +
> >>>> +       return ret;
> >>>> +}
> >>>> +
> >>>> +static int exynos_powerdown_cpu1(void)
> >>>> +{
> >>>> +       int ret = -1;
> >>>> +
> >>>> +       /*
> >>>> +        * Idle sequence for cpu1
> >>>> +        */
> >>>> +       if (cpu_pm_enter())
> >>>> +               goto cpu1_aborted;
> >>>> +
> >>>> +       /*
> >>>> +        * Turn off cpu 1
> >>>> +        */
> >>>> +       __raw_writel(0, S5P_ARM_CORE1_CONFIGURATION);
> >>>> +
> >>>> +       ret = cpu_suspend(0, cpu_suspend_finish);
> >>>> +
> >>>> +       cpu_pm_exit();
> >>>> +
> >>>> +cpu1_aborted:
> >>>> +       dsb();
> >>>> +       /*
> >>>> +        * Notify cpu 0 that cpu 1 is awake
> >>>> +        */
> >>>> +       atomic_set(&cpu1_wakeup, 1);
> >>>> +
> >>>> +       return ret;
> >>>> +}
> >>>> +
> >>>> +static int exynos_enter_aftr(struct cpuidle_device *dev,
> >>>> +                            struct cpuidle_driver *drv, int
> >>>> index) +{
> >>>> +       int ret;
> >>>> +
> >>>> +       __raw_writel(virt_to_phys(s3c_cpu_resume), BOOT_VECTOR);
> >>>> +
> >>>> +       /*
> >>>> +        * 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_powerdown_cpu1() :
> >>>> exynos_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); +
> >>>> +       atomic_set(&cpu1_wakeup, 0);
> >>>> +
> >>>> +       return index;
> >>>> +}
> >>>> +
> >>>> +static struct cpuidle_driver exynos_idle_driver = {
> >>>> +       .name           = "exynos4210_idle",
> >>>> +       .owner          = THIS_MODULE,
> >>>> +       .states = {
> >>>> +               ARM_CPUIDLE_WFI_STATE,
> >>>> +               [1] = {
> >>>> +                       .enter                  =
> >>>> exynos_enter_aftr,
> >>>> +                       .exit_latency           = 5000,
> >>>> +                       .target_residency       = 10000,
> >>>> +                       .flags                  =
> >>>> CPUIDLE_FLAG_TIME_VALID |
> >>>> +                       CPUIDLE_FLAG_COUPLED |
> >>>> CPUIDLE_FLAG_TIMER_STOP,
> >>>> +                       .name                   = "C1",
> >>>> +                       .desc                   = "ARM power
> >>>> down",
> >>>> +               },
> >>>> +       },
> >>>> +       .state_count = 2,
> >>>> +       .safe_state_index = 0,
> >>>> +};
> >>>> +
> >>>> +static int exynos_cpuidle_probe(struct platform_device *pdev)
> >>>> +{
> >>>> +       exynos_aftr = (void *)(pdev->dev.platform_data);
> >>>> +
> >>>> +       return cpuidle_register(&exynos_idle_driver,
> >>>> cpu_possible_mask); +}
> >>>> +
> >>>> +static struct platform_driver exynos_cpuidle_driver = {
> >>>> +       .driver = {
> >>>> +               .name = "exynos4210-cpuidle",
> >>>> +               .owner = THIS_MODULE,
> >>>> +       },
> >>>> +       .probe = exynos_cpuidle_probe,
> >>>> +};
> >>>> +
> >>>> +module_platform_driver(exynos_cpuidle_driver);
> >>>> --
> >>>> 1.7.9.5
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> linux-arm-kernel mailing list
> >>>> linux-arm-kernel at lists.infradead.org
> >>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >>>
> >>>
> >>>
> >>
> >>
> >
> >
> >
> 
> 

Best regards,

Lukasz Majewski
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