linux-kernel - Re: [RFT PATCH v2 07/10] drivers: qcom: rpmh-rsc: Warning if tcs

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Date:   Thu, 2 Apr 2020 13:19:38 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Maulik Shah <mkshah@...eaurora.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Evan Green <evgreen@...omium.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFT PATCH v2 07/10] drivers: qcom: rpmh-rsc: Warning if
 tcs_write() used for non-active

Hi,

On Wed, Apr 1, 2020 at 5:40 AM Maulik Shah <mkshah@...eaurora.org> wrote:
>
> Hi,
>
> On 3/12/2020 4:43 AM, Douglas Anderson wrote:
> > tcs_write() is documented to only be useful for writing
> > RPMH_ACTIVE_ONLY_STATE.  Let's be loud if someone messes up.
> >
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > ---
> >
> > Changes in v2: None
> >
> >   drivers/soc/qcom/rpmh-rsc.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> > index 93f5d1fb71ca..ba489d18c20e 100644
> > --- a/drivers/soc/qcom/rpmh-rsc.c
> > +++ b/drivers/soc/qcom/rpmh-rsc.c
> > @@ -573,6 +573,12 @@ static int tcs_write(struct rsc_drv *drv, const struct tcs_request *msg)
> >       unsigned long flags;
> >       int ret;
> >
> > +     /*
> > +      * It only makes sense to grab a whole TCS for ourselves if we're
> > +      * triggering right away, which we only do for ACTIVE_ONLY.
> > +      */
> > +     WARN_ON(msg->state != RPMH_ACTIVE_ONLY_STATE);
> > +
>
> Unnecessary check, we will never hit this warning. Lets not add such check.

That's fine.  I can drop it, especially now that comments explain that
this is only for ACTIVE_ONLY.  Personally I like having extra
assertion failures like this that indicate a serious internal logic
error in the code, but I won't push strongly for it.


> Saying that you can modify this change to drop below check  from
> rpmh_rsc_write_ctrl_data() as that never hit.
>
>          /* Data sent to this API will not be sent immediately */
>          if (msg->state == RPMH_ACTIVE_ONLY_STATE)
>                  return -EINVAL;
>
> we always call rpmh_rsc_write_ctrl_data() for RPMH_SLEEP_STATE and
> RPMH_WAKE_ONLY_STATE.

Sure.  My preference would have been to change it to a WARN_ON() too
(because it signifies an internal error within the RPMH driver, not an
external error that a client of RPMH could trigger), but I can just
drop it entirely.


-Doug