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Date:   Sun, 12 Apr 2020 19:34:02 +0530
From:   Maulik Shah <mkshah@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>, bjorn.andersson@...aro.org,
        dianders@...omium.org, evgreen@...omium.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        agross@...nel.org, mka@...omium.org, rnayak@...eaurora.org,
        ilina@...eaurora.org, lsrao@...eaurora.org
Subject: Re: [PATCH v16 4/6] soc: qcom: rpmh: Invoke rpmh_flush() for dirty
 caches

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@...eaurora.org>
>> Reviewed-by: Douglas Anderson <dianders@...omium.org>
>> 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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