Re: [PATCH V4] cpufreq: suspend governors on system suspend/hibernate

Rafael J. Wysocki
2013-11-28T14:23:33Z

On Wednesday, November 27, 2013 09:09:42 AM Viresh Kumar wrote:
> This patch adds cpufreq callbacks to dpm_{suspend|resume}_noirq() for handling
> suspend/resume of cpufreq governors.
>
> There are multiple problems that are fixed by this patch:
> - Nishanth Menon (TI) found an interesting problem on his platform, OMAP. His board
> wasn't working well with suspend/resume as calls for removing non-boot CPUs
> was turning out into a call to drivers ->target() which then tries to play
> with regulators. But regulators and their I2C bus were already suspended and
> this resulted in a failure. Many platforms have such problems, samsung, tegra,
> etc.. They solved it with driver specific PM notifiers where they used to
> disable their driver's ->target() routine.

I don't think that the Nishanth's issue is fixed by this particular version of
the patch, so I modified the changelog and removed a the comment above
cpufreq_suspend() (which should be a proper kerneldoc one if any, BTW).

I've also made some minor changes to the conditionals, because I didn't like them
the way they were written originally.

Please check the result in bleeding-edge.

Thanks!

> - Lan Tianyu (Intel) & Jinhyuk Choi (Broadcom) found another issue where
> tunables configuration for clusters/sockets with non-boot CPUs was getting
> lost after suspend/resume, as we were notifying governors with
> CPUFREQ_GOV_POLICY_EXIT on removal of the last cpu for that policy and so
> deallocating memory for tunables. This is also fixed with this patch as we
> don't allow any operation on Governors during suspend/resume now.
>
> Reported-and-tested-by: Lan Tianyu <tianyu.lan@intel.com>
> Reported-and-tested-by: Nishanth Menon <nm@ti.com>
> Reported-by: Jinhyuk Choi <jinchoi@broadcom.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---
>
> This is almost same as 1/6 of V3 version of this patchset:
>
> https://lkml.org/lkml/2013/11/25/838
>
> This is done to get some initial fixes for 3.13. These are already tested by
> both the reporters of initial problems. Tegra/exynos/s5p will keep running their
> PM notifiers until v3.14, as they are currently able to work with them..
>
> drivers/base/power/main.c | 3 +++
> drivers/cpufreq/cpufreq.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/cpufreq.h | 8 ++++++++
> 3 files changed, 61 insertions(+)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 1b41fca..e3219df 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -29,6 +29,7 @@
> #include <linux/async.h>
> #include <linux/suspend.h>
> #include <trace/events/power.h>
> +#include <linux/cpufreq.h>
> #include <linux/cpuidle.h>
> #include <linux/timer.h>
>
> @@ -540,6 +541,7 @@ static void dpm_resume_noirq(pm_message_t state)
> dpm_show_time(starttime, state, "noirq");
> resume_device_irqs();
> cpuidle_resume();
> + cpufreq_resume();
> }
>
> /**
> @@ -955,6 +957,7 @@ static int dpm_suspend_noirq(pm_message_t state)
> ktime_t starttime = ktime_get();
> int error = 0;
>
> + cpufreq_suspend();
> cpuidle_pause();
> suspend_device_irqs();
> mutex_lock(&dpm_list_mtx);
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 02d534d..b6c7821 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -26,6 +26,7 @@
> #include <linux/module.h>
> #include <linux/mutex.h>
> #include <linux/slab.h>
> +#include <linux/suspend.h>
> #include <linux/syscore_ops.h>
> #include <linux/tick.h>
> #include <trace/events/power.h>
> @@ -47,6 +48,9 @@ static LIST_HEAD(cpufreq_policy_list);
> static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
> #endif
>
> +/* Flag to suspend/resume CPUFreq governors */
> +static bool cpufreq_suspended;
> +
> static inline bool has_target(void)
> {
> return cpufreq_driver->target_index || cpufreq_driver->target;
> @@ -1462,6 +1466,48 @@ static struct subsys_interface cpufreq_interface = {
> .remove_dev = cpufreq_remove_dev,
> };
>
> +/*
> + * Callbacks for suspending/resuming governors as some platforms can't change
> + * frequency after this point in suspend cycle. Because some of the devices
> + * (like: i2c, regulators, etc) they use for changing frequency are suspended
> + * quickly after this point.
> + */
> +void cpufreq_suspend(void)
> +{
> + struct cpufreq_policy *policy;
> +
> + if (!has_target())
> + return;
> +
> + pr_debug("%s: Suspending Governors\n", __func__);
> +
> + list_for_each_entry(policy, &cpufreq_policy_list, policy_list)
> + if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP))
> + pr_err("%s: Failed to stop governor for policy: %p\n",
> + __func__, policy);
> +
> + cpufreq_suspended = true;
> +}
> +
> +void cpufreq_resume(void)
> +{
> + struct cpufreq_policy *policy;
> +
> + if (!has_target())
> + return;
> +
> + pr_debug("%s: Resuming Governors\n", __func__);
> +
> + cpufreq_suspended = false;
> +
> + list_for_each_entry(policy, &cpufreq_policy_list, policy_list)
> + if (__cpufreq_governor(policy, CPUFREQ_GOV_START) ||
> + __cpufreq_governor(policy,
> + CPUFREQ_GOV_LIMITS))
> + pr_err("%s: Failed to start governor for policy: %p\n",
> + __func__, policy);
> +}
> +
> /**
> * cpufreq_bp_suspend - Prepare the boot CPU for system suspend.
> *
> @@ -1764,6 +1810,10 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
> struct cpufreq_governor *gov = NULL;
> #endif
>
> + /* Don't start any governor operations if we are entering suspend */
> + if (cpufreq_suspended)
> + return 0;
> +
> if (policy->governor->max_transition_latency &&
> policy->cpuinfo.transition_latency >
> policy->governor->max_transition_latency) {
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index dc196bb..ee5fe9d 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -280,6 +280,14 @@ cpufreq_verify_within_cpu_limits(struct cpufreq_policy *policy)
> policy->cpuinfo.max_freq);
> }
>
> +#ifdef CONFIG_CPU_FREQ
> +void cpufreq_suspend(void);
> +void cpufreq_resume(void);
> +#else
> +static inline void cpufreq_suspend(void) {}
> +static inline void cpufreq_resume(void) {}
> +#endif
> +
> /*********************************************************************
> * CPUFREQ NOTIFIER INTERFACE *
> *********************************************************************/
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.