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From: Maulik Shah <mkshah@codeaurora.org>
To: Doug Anderson <dianders@chromium.org>
Cc: Stephen Boyd <swboyd@chromium.org>,
	Evan Green <evgreen@chromium.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Andy Gross <agross@kernel.org>,
	Matthias Kaehlcke <mka@chromium.org>,
	Rajendra Nayak <rnayak@codeaurora.org>,
	Lina Iyer <ilina@codeaurora.org>,
	lsrao@codeaurora.org
Subject: Re: [PATCH v14 6/6] soc: qcom: rpmh-rsc: Allow using free WAKE TCS for active request
Date: Fri, 27 Mar 2020 17:34:26 +0530	[thread overview]
Message-ID: <8d19958d-7334-ca4e-d7ba-f5919a56b279@codeaurora.org> (raw)
In-Reply-To: <CAD=FV=Vbo3JC6mBJXq+q+DQPC_bbNtn3bbScG5N8wzJZm87YuA@mail.gmail.com>

Hi,

On 3/27/2020 3:16 AM, Doug Anderson wrote:
> Hi,
>
> On Thu, Mar 26, 2020 at 10:38 AM Maulik Shah <mkshah@codeaurora.org> wrote:
>> When there are more than one WAKE TCS available and there is no dedicated
>> ACTIVE TCS available, invalidating all WAKE TCSes and waiting for current
>> transfer to complete in first WAKE TCS blocks using another free WAKE TCS
>> to complete current request.
>>
>> Remove rpmh_rsc_invalidate() to happen from tcs_write() when WAKE TCSes
>> is re-purposed to be used for Active mode. Clear only currently used
>> WAKE TCS's register configuration.
>>
>> Mark the caches as dirty so next time when rpmh_flush() is invoked it
>> can invalidate and program cached sleep and wake sets again.
>>
>> Fixes: 2de4b8d33eab (drivers: qcom: rpmh-rsc: allow active requests from wake TCS)
>> Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
>> ---
>>  drivers/soc/qcom/rpmh-rsc.c | 29 +++++++++++++++++++----------
>>  1 file changed, 19 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
>> index 8fa70b4..c0513af 100644
>> --- a/drivers/soc/qcom/rpmh-rsc.c
>> +++ b/drivers/soc/qcom/rpmh-rsc.c
>> @@ -154,8 +154,9 @@ int rpmh_rsc_invalidate(struct rsc_drv *drv)
>>  static struct tcs_group *get_tcs_for_msg(struct rsc_drv *drv,
>>                                          const struct tcs_request *msg)
>>  {
>> -       int type, ret;
>> +       int type;
>>         struct tcs_group *tcs;
>> +       unsigned long flags;
>>
>>         switch (msg->state) {
>>         case RPMH_ACTIVE_ONLY_STATE:
>> @@ -175,18 +176,18 @@ static struct tcs_group *get_tcs_for_msg(struct rsc_drv *drv,
>>          * If we are making an active request on a RSC that does not have a
>>          * dedicated TCS for active state use, then re-purpose a wake TCS to
>>          * send active votes.
>> -        * NOTE: The driver must be aware that this RSC does not have a
>> -        * dedicated AMC, and therefore would invalidate the sleep and wake
>> -        * TCSes before making an active state request.
>> +        *
>> +        * NOTE: Mark caches as dirty here since existing data in wake TCS will
>> +        * be lost. rpmh_flush() will processed for dirty caches to restore
>> +        * data.
>>          */
>>         tcs = get_tcs_of_type(drv, type);
>>         if (msg->state == RPMH_ACTIVE_ONLY_STATE && !tcs->num_tcs) {
>>                 tcs = get_tcs_of_type(drv, WAKE_TCS);
>> -               if (tcs->num_tcs) {
>> -                       ret = rpmh_rsc_invalidate(drv);
>> -                       if (ret)
>> -                               return ERR_PTR(ret);
>> -               }
>> +
>> +               spin_lock_irqsave(&drv->client.cache_lock, flags);
>> +               drv->client.dirty = true;
>> +               spin_unlock_irqrestore(&drv->client.cache_lock, flags);
> This seems like a huge abstraction violation.  

Agree that cache_lock and dirty flag are used in rpmh.c

I will address this to either notify rpmh.c to mark it dirty or think of other solution.

> Why can't rpmh_write()
> / rpmh_write_async() / rpmh_write_batch() just always unconditionally
> mark the cache dirty?  Are there really lots of cases when those calls
> are made and they do nothing?

At rpmh.c, it doesn't know that rpmh-rsc.c worked on borrowed TCS to finish the request.

We should not blindly mark caches dirty everytime.

>
>
> Other than that this patch seems sane to me and addresses one of the
> comments I had in:
>
> https://lore.kernel.org/r/CAD=FV=XmBQb8yfx14T-tMQ68F-h=3UHog744b3X3JZViu15+4g@mail.gmail.com
>
> ...interestingly after your patch I guess now I guess tcs_invalidate()
> no longer needs spinlocks since it's only ever called from PM code on
> the last CPU.  ...if you agree, I can always do it in my cleanup
> series.  See:
>
> https://lore.kernel.org/r/CAD=FV=Xp1o68HnC2-hMnffDDsi+jjgc9pNrdNuypjQZbS5K4nQ@mail.gmail.com
>
> -Doug

There are other RSCs which use same driver, so lets keep spinlock.

I still didn't get chance to validate your patch (i will have update sometime next week), just to update I have never seen any issue internally

using spin_lock even on nosmp case, that might require it to change to _irq_save/restore variant.

Thanks,
Maulik

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

  reply	other threads:[~2020-03-27 12:04 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-26 17:37 [PATCH v14 0/6] Invoke rpmh_flush for non OSI targets Maulik Shah
2020-03-26 17:37 ` [PATCH v14 1/6] arm64: dts: qcom: sc7180: Add cpuidle low power states Maulik Shah
2020-03-26 17:37 ` [PATCH v14 2/6] soc: qcom: rpmh: Update dirty flag only when data changes Maulik Shah
2020-03-26 17:37 ` [PATCH v14 3/6] soc: qcom: rpmh: Invalidate SLEEP and WAKE TCSes before flushing new data Maulik Shah
2020-03-26 18:31   ` Doug Anderson
2020-03-27  8:23     ` Maulik Shah
2020-03-26 17:37 ` [PATCH v14 4/6] soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches Maulik Shah
2020-03-26 21:18   ` Doug Anderson
     [not found]     ` <7bd2c923-4003-a1c4-610f-548e79a94d35@codeaurora.org>
2020-03-27 18:22       ` Doug Anderson
2020-03-31  8:26         ` Maulik Shah
2020-03-26 17:37 ` [PATCH v14 5/6] soc: qcom: rpmh-rsc: Clear active mode configuration for wake TCS Maulik Shah
2020-03-26 18:20   ` Doug Anderson
2020-03-26 17:37 ` [PATCH v14 6/6] soc: qcom: rpmh-rsc: Allow using free WAKE TCS for active request Maulik Shah
2020-03-26 21:46   ` Doug Anderson
2020-03-27 12:04     ` Maulik Shah [this message]
2020-03-27 18:42       ` Doug Anderson
2020-03-31  8:57         ` Maulik Shah

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