Re: [PATCH 1/7] cpufreq: remove redundant CPUFREQ_INCOMPATIBLE notifier event

From: Rafael J. Wysocki
Date: Wed Sep 09 2015 - 18:58:59 EST

On Monday, August 03, 2015 08:36:14 AM Viresh Kumar wrote:
> What's being done from CPUFREQ_INCOMPATIBLE, can also be done with
> CPUFREQ_ADJUST. There is nothing special with CPUFREQ_INCOMPATIBLE
> notifier.

The above part of the changelog is a disaster to me. :-(

It not only doesn't explain what really goes on, but it's actively confusing.

What really happens is that the core sends CPUFREQ_INCOMPATIBLE notifications
unconditionally right after sending the CPUFREQ_ADJUST ones, so the former is
just redundant and it's more efficient to merge the two into one.

> Kill CPUFREQ_INCOMPATIBLE and fix its usage sites.
>
> This also updates the numbering of notifier events to remove holes.

Why don't you redefine CPUFREQ_ADJUST as 1 instead?

> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> Documentation/cpu-freq/core.txt | 7 ++-----
> drivers/acpi/processor_perflib.c | 2 +-
> drivers/cpufreq/cpufreq.c | 4 ----
> drivers/cpufreq/ppc_cbe_cpufreq_pmi.c | 4 ++--
> drivers/video/fbdev/pxafb.c | 1 -
> drivers/video/fbdev/sa1100fb.c | 1 -
> include/linux/cpufreq.h | 9 ++++-----
> 7 files changed, 9 insertions(+), 19 deletions(-)
>
> diff --git a/Documentation/cpu-freq/core.txt b/Documentation/cpu-freq/core.txt
> index 70933eadc308..ba78e7c2a069 100644
> --- a/Documentation/cpu-freq/core.txt
> +++ b/Documentation/cpu-freq/core.txt
> @@ -55,16 +55,13 @@ transition notifiers.
> ----------------------------
>
> These are notified when a new policy is intended to be set. Each
> -CPUFreq policy notifier is called three times for a policy transition:
> +CPUFreq policy notifier is called twice for a policy transition:
>
> 1.) During CPUFREQ_ADJUST all CPUFreq notifiers may change the limit if
> they see a need for this - may it be thermal considerations or
> hardware limitations.
>
> -2.) During CPUFREQ_INCOMPATIBLE only changes may be done in order to avoid
> - hardware failure.
> -
> -3.) And during CPUFREQ_NOTIFY all notifiers are informed of the new policy
> +2.) And during CPUFREQ_NOTIFY all notifiers are informed of the new policy
> - if two hardware drivers failed to agree on a new policy before this
> stage, the incompatible hardware shall be shut down, and the user
> informed of this.
> diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
> index 47af702bb6a2..bb01dea39fdc 100644
> --- a/drivers/acpi/processor_perflib.c
> +++ b/drivers/acpi/processor_perflib.c
> @@ -83,7 +83,7 @@ static int acpi_processor_ppc_notifier(struct notifier_block *nb,
> if (ignore_ppc)
> return 0;
>
> - if (event != CPUFREQ_INCOMPATIBLE)
> + if (event != CPUFREQ_ADJUST)
> return 0;
>
> mutex_lock(&performance_mutex);
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 76a26609d96b..293f47b814bf 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2206,10 +2206,6 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
> CPUFREQ_ADJUST, new_policy);
>
> - /* adjust if necessary - hardware incompatibility*/
> - blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
> - CPUFREQ_INCOMPATIBLE, new_policy);
> -
> /*
> * verify the cpu speed can be set within this limit, which might be
> * different to the first one
> diff --git a/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c b/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c
> index d29e8da396a0..7969f7690498 100644
> --- a/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c
> +++ b/drivers/cpufreq/ppc_cbe_cpufreq_pmi.c
> @@ -97,8 +97,8 @@ static int pmi_notifier(struct notifier_block *nb,
> struct cpufreq_frequency_table *cbe_freqs;
> u8 node;
>
> - /* Should this really be called for CPUFREQ_ADJUST, CPUFREQ_INCOMPATIBLE
> - * and CPUFREQ_NOTIFY policy events?)
> + /* Should this really be called for CPUFREQ_ADJUST and CPUFREQ_NOTIFY
> + * policy events?)
> */
> if (event == CPUFREQ_START)
> return 0;
> diff --git a/drivers/video/fbdev/pxafb.c b/drivers/video/fbdev/pxafb.c
> index 7245611ec963..94813af97f09 100644
> --- a/drivers/video/fbdev/pxafb.c
> +++ b/drivers/video/fbdev/pxafb.c
> @@ -1668,7 +1668,6 @@ pxafb_freq_policy(struct notifier_block *nb, unsigned long val, void *data)
>
> switch (val) {
> case CPUFREQ_ADJUST:
> - case CPUFREQ_INCOMPATIBLE:
> pr_debug("min dma period: %d ps, "
> "new clock %d kHz\n", pxafb_display_dma_period(var),
> policy->max);
> diff --git a/drivers/video/fbdev/sa1100fb.c b/drivers/video/fbdev/sa1100fb.c
> index 89dd7e02197f..dcf774c15889 100644
> --- a/drivers/video/fbdev/sa1100fb.c
> +++ b/drivers/video/fbdev/sa1100fb.c
> @@ -1042,7 +1042,6 @@ sa1100fb_freq_policy(struct notifier_block *nb, unsigned long val,
>
> switch (val) {
> case CPUFREQ_ADJUST:
> - case CPUFREQ_INCOMPATIBLE:
> dev_dbg(fbi->dev, "min dma period: %d ps, "
> "new clock %d kHz\n", sa1100fb_min_dma_period(fbi),
> policy->max);
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index bde1e567b3a9..bedcc90c0757 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -369,11 +369,10 @@ static inline void cpufreq_resume(void) {}
>
> /* Policy Notifiers */
> #define CPUFREQ_ADJUST (0)
> -#define CPUFREQ_INCOMPATIBLE (1)
> -#define CPUFREQ_NOTIFY (2)
> -#define CPUFREQ_START (3)
> -#define CPUFREQ_CREATE_POLICY (4)
> -#define CPUFREQ_REMOVE_POLICY (5)
> +#define CPUFREQ_NOTIFY (1)
> +#define CPUFREQ_START (2)
> +#define CPUFREQ_CREATE_POLICY (3)
> +#define CPUFREQ_REMOVE_POLICY (4)
>
> #ifdef CONFIG_CPU_FREQ
> int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list);
>

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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