[RFC PATCH v4 2/4] ARM: omap: Remove cpuidle timekeeping and irq enable/disable

[Jean Pihet]

Rob,

On Wed, Feb 1, 2012 at 4:00 AM, Robert Lee <rob.lee at linaro.org> wrote:
> Now that the core cpuidle driver keeps time and handles irq enabling,
> remove this functionality.  Also, remove irq disabling as all paths to
> cpuidle_idle_call already call local_irq_disable.  Also, restructure
> idle functions as needed by the cpuidle core driver changes.
>
> Signed-off-by: Robert Lee <rob.lee at linaro.org>
> ---
>  arch/arm/mach-omap2/cpuidle34xx.c |   96 ++++++++++++++++--------------------
>  1 files changed, 43 insertions(+), 53 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/cpuidle34xx.c b/arch/arm/mach-omap2/cpuidle34xx.c
> index 464cffd..9ecded5 100644
> --- a/arch/arm/mach-omap2/cpuidle34xx.c
> +++ b/arch/arm/mach-omap2/cpuidle34xx.c
...

> @@ -100,23 +107,20 @@ static int omap3_enter_idle(struct cpuidle_device *dev,
>                                struct cpuidle_driver *drv,
>                                int index)
>  {
> -       struct omap3_idle_statedata *cx =
> -                       cpuidle_get_statedata(&dev->states_usage[index]);
> -       struct timespec ts_preidle, ts_postidle, ts_idle;
> -       u32 mpu_state = cx->mpu_state, core_state = cx->core_state;
> -       int idle_time;
> +       struct omap3_idle_drvdata *dd = dev->states_usage[index].driver_data
A build error is triggered by the missing ";".

...

> @@ -147,18 +151,12 @@ static int omap3_enter_idle(struct cpuidle_device *dev,
>                pwrdm_for_each_clkdm(core_pd, _cpuidle_allow_idle);
>        }
>
> -return_sleep_time:
> -       getnstimeofday(&ts_postidle);
> -       ts_idle = timespec_sub(ts_postidle, ts_preidle);
> -
> -       local_irq_enable();
> +leave:
>        local_fiq_enable();
>
> -       idle_time = ts_idle.tv_nsec / NSEC_PER_USEC + ts_idle.tv_sec * \
> -                                                               USEC_PER_SEC;
> -
> -       /* Update cpuidle counters */
> -       dev->last_residency = idle_time;
> +       /* Restore original PER state if it was modified */
> +       if (dd->per_next_state != dd->per_saved_state)
> +               pwrdm_set_next_pwrst(per_pd, dd->per_saved_state);
This code is not necessarily balanced with the PER state change in
omap3_enter_idle_bm (cf. "/* Are we changing PER target state? */"
here below), since in the core cpuidle code there is no guarantee that
the calls to pre_enter and enter callbacks are balanced.
In general I fear that splitting the code in two functions introduces
a risk of programming non-coherent settings in the PRCM.

...

> @@ -255,8 +255,9 @@ static int omap3_enter_idle_bm(struct cpuidle_device *dev,
>                               int index)
>  {
>        int new_state_idx;
> -       u32 core_next_state, per_next_state = 0, per_saved_state = 0, cam_state;
> -       struct omap3_idle_statedata *cx;
> +       u32 core_next_state, cam_state;
> +       struct omap3_idle_drvdata *dd = dev->states_usage[index].driver_data;
> +       struct omap3_idle_statedata *cx = &dd->state_data[index];
>        int ret;
The build throws a few warnings about unused variables:

arch/arm/mach-omap2/cpuidle34xx.c: In function 'omap3_enter_idle_bm':
arch/arm/mach-omap2/cpuidle34xx.c:261: warning: unused variable 'ret'
arch/arm/mach-omap2/cpuidle34xx.c:257: warning: unused variable 'new_state_idx'

...

>
>  DEFINE_PER_CPU(struct cpuidle_device, omap3_idle_dev);
> @@ -337,7 +329,8 @@ static inline void _fill_cstate(struct cpuidle_driver *drv,
>        state->exit_latency     = cpuidle_params_table[idx].exit_latency;
>        state->target_residency = cpuidle_params_table[idx].target_residency;
>        state->flags            = CPUIDLE_FLAG_TIME_VALID;
> -       state->enter            = omap3_enter_idle_bm;
> +       state->pre_enter        = omap3_enter_idle_bm;
> +       state->enter            = omap3_enter_idle;
>        sprintf(state->name, "C%d", idx + 1);
>        strncpy(state->desc, descr, CPUIDLE_DESC_LEN);
>
...

Also the line at 373 is not needed anymore in omap3_idle_init, since
the enter callback is filled in in the _fill_cstate function:
        /* C1 . MPU WFI + Core active */
        _fill_cstate(drv, 0, "MPU ON + CORE ON");
        (&drv->states[0])->enter = omap3_enter_idle;             <==
not needed anymore
        drv->safe_state_index = 0;

More testing on OMAP3 is needed. Let me come back with the results asap.

Regards,
Jean