linux-kernel - Re: [PATCH v6 5/8] drm/msm/dp: prevent multiple votes for dp resources

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Message-ID: <CAA8EJppMnDR15ZSS7FyMvDH0yshfNtgZgoYaxpYkJ3=xYm+Ggw@mail.gmail.com>
Date:   Fri, 8 Apr 2022 21:02:24 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Sankeerth Billakanti <sbillaka@....qualcomm.com>
Cc:     Doug Anderson <dianders@...omium.org>,
        "Sankeerth Billakanti (QUIC)" <quic_sbillaka@...cinc.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Clark <robdclark@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        quic_kalyant <quic_kalyant@...cinc.com>,
        "Abhinav Kumar (QUIC)" <quic_abhinavk@...cinc.com>,
        "Kuogee Hsieh (QUIC)" <quic_khsieh@...cinc.com>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        quic_vproddut <quic_vproddut@...cinc.com>,
        "Aravind Venkateswaran (QUIC)" <quic_aravindh@...cinc.com>
Subject: Re: [PATCH v6 5/8] drm/msm/dp: prevent multiple votes for dp resources

On Fri, 8 Apr 2022 at 20:12, Sankeerth Billakanti
<sbillaka@....qualcomm.com> wrote:
>
> > > On Wed, Mar 30, 2022 at 9:04 AM Sankeerth Billakanti
> > > <quic_sbillaka@...cinc.com> wrote:
> > >>
> > >> The aux_bus support with the dp_display driver will enable the dp
> > >> resources during msm_dp_modeset_init. The host_init has to return
> > >> early if the core is already initialized to prevent putting an
> > >> additional vote for the dp controller resources.
> > >>
> > >> Signed-off-by: Sankeerth Billakanti <quic_sbillaka@...cinc.com>
> > >> ---
> > >>   drivers/gpu/drm/msm/dp/dp_display.c | 10 ++++++++++
> > >>   1 file changed, 10 insertions(+)
> > >
> > > I'm not a huge fan of this but I'll leave it up to Dmitry. In general
> > > it feels like there should be _a_ place that enables these resources.
> > > Checks like this make it feel like we just scattershot enabling
> > > resources in a bunch of random places instead of coming up with the
> > > design for enabling them in the right place.
> >
> > I'd prefer to see a check for eDP in dp_display_config_hpd(). Or even better
> > to see that this function isn't called for eDP at all.
> >
>
> This needs to be called when eDP is not using the aux_bus path. If the eDP panel is
> given as a separate panel driver, then the resources need to be enabled here.
>
> If we don't want to support eDP without aux_bus, then we can skip this function.

I think it's up to you to decide, if it's necessary or not.
But if it is, please change it accordingly.

> > >
> > > In any case, if we do end up landing this patch, it sure feels like it
> > > needs to move earlier in the patch series, right? This patch shouldn't
> > > hurt even without the other patches in the series but if you apply the
> > > earlier patches in the series without this one then you'll have a bug,
> > > right? That means this needs to come earlier.
> > >
> > > -Doug
> >
> >
> > --
> > With best wishes
> > Dmitry
>
> Thank you,
> Sankeerth



-- 
With best wishes
Dmitry