On Monday, November 25, 2013 07:41:41 PM Viresh Kumar wrote:
>
> This patch adds cpufreq callbacks to dpm_{suspend|resume}() for handling
> suspend/resume of cpufreq governors. This is required for early suspend and
> late resume of governors and cpufreq core.
>
> 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.
>
> - 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 don't
> allow any operation on Governors during suspend/resume now.
>
> Reported-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
> Reported-by: Nishanth Menon <nm@xxxxxx>
> Reported-by: Jinhyuk Choi <jinchoi@xxxxxxxxxxxx>
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
>
> ---
> drivers/base/power/main.c | 5 +++++
>
> drivers/cpufreq/cpufreq.c | 50
> +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/cpufreq.h
> | 3 +++
> 3 files changed, 58 insertions(+)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 1b41fca..c9fbb9d 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>
>
> @@ -789,6 +790,8 @@ void dpm_resume(pm_message_t state)
>
> mutex_unlock(&dpm_list_mtx);
> async_synchronize_full();
> dpm_show_time(starttime, state, NULL);
>
> +
> + cpufreq_resume();
>
> }
>
> /**
>
> @@ -1259,6 +1262,8 @@ int dpm_suspend(pm_message_t state)
>
> might_sleep();
>
> + cpufreq_suspend();
> +
>
> mutex_lock(&dpm_list_mtx);
> pm_transition = state;
> async_error = 0;
Shouldn't it do cpufreq_resume() on errors?
> 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);
This appears to be racy. Is it really racy, or just seemingly?
> +
> + 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..6d93f91 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -255,6 +255,9 @@ struct cpufreq_driver {
>
> int cpufreq_register_driver(struct cpufreq_driver *driver_data);
> int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);
>
> +void cpufreq_suspend(void);
> +void cpufreq_resume(void);
> +
>
> const char *cpufreq_get_current_driver(void);
>
> static inline void cpufreq_verify_within_limits(struct cpufreq_policy
> *policy,
Thanks!
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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