[Skiboot] [PATCH v2 2/3] cpuidle:powernv: Add helper function to populate powernv idle states.

Oliver O'Halloran oohall at gmail.com
Tue Nov 1 19:32:58 AEDT 2016


On Thu, Oct 27, 2016 at 7:35 PM, Gautham R. Shenoy
<ego at linux.vnet.ibm.com> wrote:
> From: "Gautham R. Shenoy" <ego at linux.vnet.ibm.com>
>
> In the current code for powernv_add_idle_states, there is a lot of code
> duplication while initializing an idle state in powernv_states table.
>
> Add an inline helper function to populate the powernv_states[] table for
> a given idle state. Invoke this for populating the "Nap", "Fastsleep"
> and the stop states in powernv_add_idle_states.
>
> Signed-off-by: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> ---
>  drivers/cpuidle/cpuidle-powernv.c | 82 +++++++++++++++++++++++----------------
>  include/linux/cpuidle.h           |  1 +
>  2 files changed, 49 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> index 7fe442c..11b22b9 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -167,6 +167,28 @@ static int powernv_cpuidle_driver_init(void)
>         return 0;
>  }
>
> +static inline void add_powernv_state(int index, const char *name,
> +                                    unsigned int flags,
> +                                    int (*idle_fn)(struct cpuidle_device *,
> +                                                   struct cpuidle_driver *,
> +                                                   int),
> +                                    unsigned int target_residency,
> +                                    unsigned int exit_latency,
> +                                    u64 psscr_val)
> +{
> +       strncpy(powernv_states[index].name, name, CPUIDLE_NAME_LEN);
> +       strncpy(powernv_states[index].desc, name, CPUIDLE_NAME_LEN);

If the supplied name is equal to CPUIDLE_NAME_LEN then strncpy() won't
terminate the string. The least annoying fix is to memset() the whole
structure to zero and set n to CPUIDLE_NAME_LEN - 1.

> +       powernv_states[index].flags = flags;
> +       powernv_states[index].target_residency = target_residency;
> +       powernv_states[index].exit_latency = exit_latency;
> +       powernv_states[index].enter = idle_fn;
> +
> +       if (idle_fn != stop_loop)
> +               return;

This can probably be deleted. The nap/sleep loops don't look at the
psscr setting and you've passed in a dummy value of zero anyway.

> +
> +       stop_psscr_table[index] = psscr_val;
> +}
> +
>  static int powernv_add_idle_states(void)
>  {
>         struct device_node *power_mgt;
> @@ -236,6 +258,7 @@ static int powernv_add_idle_states(void)
>                 "ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
>
>         for (i = 0; i < dt_idle_states; i++) {
> +               unsigned int exit_latency, target_residency;
>                 /*
>                  * If an idle state has exit latency beyond
>                  * POWERNV_THRESHOLD_LATENCY_NS then don't use it
> @@ -244,27 +267,30 @@ static int powernv_add_idle_states(void)
>                 if (latency_ns[i] > POWERNV_THRESHOLD_LATENCY_NS)
>                         continue;
>
> +               exit_latency = ((unsigned int)latency_ns[i]) / 1000;
> +               target_residency = (!rc) ? ((unsigned int)residency_ns[i]) : 0;
> +               /*
> +                * Firmware passes residency values in ns.
> +                * cpuidle expects it in us.
> +                */
> +               target_residency /= 1000;
> +
>                 /*
>                  * Cpuidle accepts exit_latency and target_residency in us.

This comment says the same thing as the one above.

>                  * Use default target_residency values if f/w does not expose it.
>                  */
>                 if (flags[i] & OPAL_PM_NAP_ENABLED) {
> +                       target_residency = 100;

Hmm, the above comment says that we should only use the default value
for target_residency if firmware hasn't provided a value. Is there a
reason we always use the hard coded value?

>                         /* Add NAP state */
> -                       strcpy(powernv_states[nr_idle_states].name, "Nap");
> -                       strcpy(powernv_states[nr_idle_states].desc, "Nap");
> -                       powernv_states[nr_idle_states].flags = 0;
> -                       powernv_states[nr_idle_states].target_residency = 100;
> -                       powernv_states[nr_idle_states].enter = nap_loop;
> +                       add_powernv_state(nr_idle_states, "Nap",
> +                                         CPUIDLE_FLAG_NONE, nap_loop,
> +                                         target_residency, exit_latency, 0);
>                 } else if ((flags[i] & OPAL_PM_STOP_INST_FAST) &&
>                                 !(flags[i] & OPAL_PM_TIMEBASE_STOP)) {
> -                       strncpy(powernv_states[nr_idle_states].name,
> -                               names[i], CPUIDLE_NAME_LEN);
> -                       strncpy(powernv_states[nr_idle_states].desc,
> -                               names[i], CPUIDLE_NAME_LEN);
> -                       powernv_states[nr_idle_states].flags = 0;
> -
> -                       powernv_states[nr_idle_states].enter = stop_loop;
> -                       stop_psscr_table[nr_idle_states] = psscr_val[i];
> +                       add_powernv_state(nr_idle_states, names[i],
> +                                         CPUIDLE_FLAG_NONE, stop_loop,
> +                                         target_residency, exit_latency,
> +                                         psscr_val[i]);
>                 }
>
>                 /*
> @@ -274,32 +300,20 @@ static int powernv_add_idle_states(void)
>  #ifdef CONFIG_TICK_ONESHOT
>                 if (flags[i] & OPAL_PM_SLEEP_ENABLED ||
>                         flags[i] & OPAL_PM_SLEEP_ENABLED_ER1) {
> +                       target_residency = 300000;

Same comment as above.

>                         /* Add FASTSLEEP state */
> -                       strcpy(powernv_states[nr_idle_states].name, "FastSleep");
> -                       strcpy(powernv_states[nr_idle_states].desc, "FastSleep");
> -                       powernv_states[nr_idle_states].flags = CPUIDLE_FLAG_TIMER_STOP;
> -                       powernv_states[nr_idle_states].target_residency = 300000;
> -                       powernv_states[nr_idle_states].enter = fastsleep_loop;
> +                       add_powernv_state(nr_idle_states, "FastSleep",
> +                                         CPUIDLE_FLAG_TIMER_STOP,
> +                                         fastsleep_loop,
> +                                         target_residency, exit_latency, 0);
>                 } else if ((flags[i] & OPAL_PM_STOP_INST_DEEP) &&
>                                 (flags[i] & OPAL_PM_TIMEBASE_STOP)) {
> -                       strncpy(powernv_states[nr_idle_states].name,
> -                               names[i], CPUIDLE_NAME_LEN);
> -                       strncpy(powernv_states[nr_idle_states].desc,
> -                               names[i], CPUIDLE_NAME_LEN);
> -
> -                       powernv_states[nr_idle_states].flags = CPUIDLE_FLAG_TIMER_STOP;
> -                       powernv_states[nr_idle_states].enter = stop_loop;
> -                       stop_psscr_table[nr_idle_states] = psscr_val[i];
> +                       add_powernv_state(nr_idle_states, names[i],
> +                                         CPUIDLE_FLAG_TIMER_STOP, stop_loop,
> +                                         target_residency, exit_latency,
> +                                         psscr_val[i]);
>                 }
>  #endif
> -               powernv_states[nr_idle_states].exit_latency =
> -                               ((unsigned int)latency_ns[i]) / 1000;
> -
> -               if (!rc) {
> -                       powernv_states[nr_idle_states].target_residency =
> -                               ((unsigned int)residency_ns[i]) / 1000;
> -               }
> -
>                 nr_idle_states++;
>         }
>  out:
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index bb31373..c4e10f8 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -62,6 +62,7 @@ struct cpuidle_state {
>  };
>
>  /* Idle State Flags */
> +#define CPUIDLE_FLAG_NONE       (0x00)
>  #define CPUIDLE_FLAG_COUPLED   (0x02) /* state applies to multiple cpus */
>  #define CPUIDLE_FLAG_TIMER_STOP (0x04)  /* timer is stopped on this state */
>
> --
> 1.9.4
>

Looks good otherwise.

Reviewed-by: Oliver O'Halloran <oohall at gmail.com>


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