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

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Date:   Fri, 8 Apr 2022 19:14:52 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Doug Anderson <dianders@...omium.org>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>
Cc:     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 <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>,
        quic_aravindh@...cinc.com
Subject: Re: [PATCH v6 5/8] drm/msm/dp: prevent multiple votes for dp
 resources

On 01/04/2022 02:23, Doug Anderson wrote:
> Hi,
> 
> 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.

> 
> 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