Re: [PATCH v16 4/6] soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches

[Maulik Shah]

Hi,

On 4/10/2020 9:45 AM, Stephen Boyd wrote:
> Quoting Maulik Shah (2020-04-05 23:32:19)
> > Add changes to invoke rpmh flush() from CPU PM notification.
> > This is done when the last the cpu is entering power collapse and
> 'power collapse' is a qcom-ism. Maybe say something like "deep CPU idle
> states"?
Okay, i updated in v17.
> > controller is not busy.
> >
> > Controllers that do have 'HW solver' mode do not need to register
> > for CPU PM notification. They may be in autonomous mode executing
> > low power mode and do not require rpmh_flush() to happen from CPU
> > PM notification.
> Can you provide an example of a HW solver mode controller? Presumably
> the display RSC is one of these?
Sure, Added in v17 to mention display RSC.
> > Signed-off-by: Maulik Shah <mkshah@xxxxxxxxxxxxxx>
> > Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> > diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> > index b718221..fbe1f3e 100644
> > --- a/drivers/soc/qcom/rpmh-rsc.c
> > +++ b/drivers/soc/qcom/rpmh-rsc.c
> > @@ -521,8 +527,86 @@ int rpmh_rsc_write_ctrl_data(struct rsc_drv *drv, const struct tcs_request *msg)
> >          return tcs_ctrl_write(drv, msg);
> >   }
> >   
> > +/**
> > + * rpmh_rsc_ctrlr_is_busy() - Check if any of the AMCs are busy.
> > + *
> > + * @drv: The controller
> > + *
> > + * Checks if any of the AMCs are busy in handling ACTIVE sets.
> > + * This is called from the last cpu powering down before flushing
> > + * SLEEP and WAKE sets. If AMCs are busy, controller can not enter
> > + * power collapse, so deny from the last cpu's pm notification.
> > + *
> > + * Return:
> > + * * False             - AMCs are idle
> > + * * True              - AMCs are busy
> > + */
> > +static bool rpmh_rsc_ctrlr_is_busy(struct rsc_drv *drv)
> Can drv be const? Would be nice to make it const in some places in this
> driver.

It can, but it will require changing multiple places to make it const. 
some of those functions are

dropped/modified in doug's cleanup series. I can do in separate patch 
once this series is pulled in.

> > +{
> > +       int m;
> > +       struct tcs_group *tcs = get_tcs_of_type(drv, ACTIVE_TCS);
> > +
> > +       /*
> > +        * If we made an active request on a RSC that does not have a
> > +        * dedicated TCS for active state use, then re-purposed wake TCSes
> > +        * should be checked for not busy.
> not busy, because we use wake TCSes for active requests in this case.
Ok, added in v17.
> > +        *
> > +        * Since this is called from the last cpu, need not take drv or tcs
> > +        * lock before checking tcs_is_free().
> > +        */
> > +       if (!tcs->num_tcs)
> > +               tcs = get_tcs_of_type(drv, WAKE_TCS);
> > +
> > +       for (m = tcs->offset; m < tcs->offset + tcs->num_tcs; m++) {
> > +               if (!tcs_is_free(drv, m))
> > +                       return true;
> > +       }
> > +
> > +       return false;
> > +}
> [...]
> > +
> > diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> > index a75f3df..88f8801 100644
> > --- a/drivers/soc/qcom/rpmh.c
> > +++ b/drivers/soc/qcom/rpmh.c
> > @@ -433,16 +430,17 @@ static int send_single(struct rpmh_ctrlr *ctrlr, enum rpmh_state state,
> >   }
> >   
> >   /**
> > - * rpmh_flush: Flushes the buffered active and sleep sets to TCS
> > + * rpmh_flush() - Flushes the buffered sleep and wake sets to TCSes
> >    *
> > - * @ctrlr: controller making request to flush cached data
> > + * @ctrlr: Controller making request to flush cached data
> >    *
> > - * Return: -EBUSY if the controller is busy, probably waiting on a response
> > - * to a RPMH request sent earlier.
> > + * This function is called from sleep code on the last CPU
> > + * (thus no spinlock needed).
> Might be good to stick a lockdep_assert_irqs_disabled() in this function
> then. That would document that this function should only be called when
> irqs are disabled.

Okay. Added lockdep_assert_irqs_disabled(). But this may need to be 
dropped when

we add support for display RSC.

> >    *
> > - * This function is always called from the sleep code from the last CPU
> > - * that is powering down the entire system. Since no other RPMH API would be
> > - * executing at this time, it is safe to run lockless.
> > + * Return:
> > + * * 0          - Success
> > + * * -EAGAIN    - Retry again
> > + * * Error code - Otherwise
> >    */
> >   int rpmh_flush(struct rpmh_ctrlr *ctrlr)
> This function name keeps throwing me off. Can we please call it
> something like rpmh_configure_tcs_sleep_wake()? The word "flush" seems
> to imply there's some sort of cache going on, but that's not really the
> case. We're programming a couple TCS FIFOs so that they can be used
> across deep CPU sleep states.
>
> >   {
> > @@ -455,9 +453,7 @@ int rpmh_flush(struct rpmh_ctrlr *ctrlr)
> >          }
> >   
> >          /* Invalidate the TCSes first to avoid stale data */
> > -       do {
> > -               ret = rpmh_rsc_invalidate(ctrlr_to_drv(ctrlr));
> > -       } while (ret == -EAGAIN);
> > +       ret = rpmh_rsc_invalidate(ctrlr_to_drv(ctrlr));
> >          if (ret)
> >                  return ret;

Thanks,

Maulik

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