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From: Doug Anderson <dianders@chromium.org>
To: Stephen Boyd <swboyd@chromium.org>
Cc: Maulik Shah <mkshah@codeaurora.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Evan Green <evgreen@chromium.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 v17 2/6] soc: qcom: rpmh: Update dirty flag only when data changes
Date: Fri, 17 Apr 2020 14:16:53 -0700	[thread overview]
Message-ID: <CAD=FV=WOwMrTNS7FK0jybJyEOvT-rHarA0m5U6B+pKoeA7RCHQ@mail.gmail.com> (raw)
In-Reply-To: <158708153779.132238.7823999141480422982@swboyd.mtv.corp.google.com>

On Thu, Apr 16, 2020 at 4:59 PM Stephen Boyd <swboyd@chromium.org> wrote:
>
> Quoting Maulik Shah (2020-04-12 07:50:00)
> > diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> > index eb0ded0..03630ae 100644
> > --- a/drivers/soc/qcom/rpmh.c
> > +++ b/drivers/soc/qcom/rpmh.c
> > @@ -133,26 +134,27 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
> >
> >         req->addr = cmd->addr;
> >         req->sleep_val = req->wake_val = UINT_MAX;
> > -       INIT_LIST_HEAD(&req->list);
> >         list_add_tail(&req->list, &ctrlr->cache);
> >
> >  existing:
> > +       old_sleep_val = req->sleep_val;
> > +       old_wake_val = req->wake_val;
> > +
> >         switch (state) {
> >         case RPMH_ACTIVE_ONLY_STATE:
> > -               if (req->sleep_val != UINT_MAX)
> > -                       req->wake_val = cmd->data;
> > -               break;
> >         case RPMH_WAKE_ONLY_STATE:
> >                 req->wake_val = cmd->data;
> >                 break;
> >         case RPMH_SLEEP_STATE:
> >                 req->sleep_val = cmd->data;
> >                 break;
> > -       default:
> > -               break;
> >         }
> >
> > -       ctrlr->dirty = true;
> > +       ctrlr->dirty = (req->sleep_val != old_sleep_val ||
> > +                       req->wake_val != old_wake_val) &&
> > +                       req->sleep_val != UINT_MAX &&
> > +                       req->wake_val != UINT_MAX;
>
> Can this change ctrl->dirty from true to false? I'm worried that we need
> to make this a saturating assignment instead of an assignment.
>
>         ctrl->dirty = ctrl->dirty || (req->sleep_val != .. );

This seems like a serious problem with the current code and feels like
we need a fix sooner rather than later.  I'm sorry I missed it in
review (and in fact, I probably suggested the exact code that's here
so it's even more my fault).  :(

I posted:

https://lore.kernel.org/r/20200417141531.1.Ia4b74158497213eabad7c3d474c50bfccb3f342e@changeid

-Doug

  reply	other threads:[~2020-04-17 21:17 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-12 14:49 [PATCH v17 0/6] Invoke rpmh_flush for non OSI targets Maulik Shah
2020-04-12 14:49 ` [PATCH v17 1/6] arm64: dts: qcom: sc7180: Add cpuidle low power states Maulik Shah
2020-04-12 14:50 ` [PATCH v17 2/6] soc: qcom: rpmh: Update dirty flag only when data changes Maulik Shah
2020-04-13 21:17   ` Stephen Boyd
2020-04-16 23:58   ` Stephen Boyd
2020-04-17 21:16     ` Doug Anderson [this message]
2020-04-12 14:50 ` [PATCH v17 3/6] soc: qcom: rpmh: Invalidate SLEEP and WAKE TCSes before flushing new data Maulik Shah
2020-04-13 21:17   ` Stephen Boyd
2020-04-12 14:50 ` [PATCH v17 4/6] soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches Maulik Shah
2020-04-13 16:17   ` Doug Anderson
2020-04-13 21:18   ` Stephen Boyd
2020-04-12 14:50 ` [PATCH v17 5/6] soc: qcom: rpmh-rsc: Clear active mode configuration for wake TCS Maulik Shah
2020-04-12 14:50 ` [PATCH v17 6/6] soc: qcom: rpmh-rsc: Allow using free WAKE TCS for active request Maulik Shah
2020-04-13 21:19   ` Stephen Boyd
2020-04-14  5:34 ` [PATCH v17 0/6] Invoke rpmh_flush for non OSI targets Bjorn Andersson
2020-04-14  9:19   ` Maulik Shah

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