linux-kernel - Re: [PATCH v1 2/3] drm/msm/dp: decoupling dp->id out of dp controller_id at scxxxx_dp

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Date:   Mon, 27 Jun 2022 18:38:58 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>, agross@...nel.org,
        airlied@...ux.ie, bjorn.andersson@...aro.org, daniel@...ll.ch,
        dianders@...omium.org, dri-devel@...ts.freedesktop.org,
        robdclark@...il.com, sean@...rly.run, vkoul@...nel.org,
        quic_aravindh@...cinc.com, quic_sbillaka@...cinc.com,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/3] drm/msm/dp: decoupling dp->id out of dp
 controller_id at scxxxx_dp_cfg table

On Mon, 27 Jun 2022 at 18:33, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
>
>
> On 6/24/2022 6:15 PM, Stephen Boyd wrote:
> > Quoting Kuogee Hsieh (2022-06-24 18:02:50)
> >> On 6/24/2022 5:46 PM, Dmitry Baryshkov wrote:
> >>> On Sat, 25 Jun 2022 at 03:28, Dmitry Baryshkov
> >>> <dmitry.baryshkov@...aro.org> wrote:
> >>>> On Sat, 25 Jun 2022 at 03:23, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
> >>>>> On 6/24/2022 5:21 PM, Dmitry Baryshkov wrote:
> >>>>>> On Sat, 25 Jun 2022 at 03:19, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
> >>>>>>> How can I have eDP call dpu_encoder_init() before DP calls with
> >>>>>>> _dpu_kms_initialize_displayport()?
> >>>>>> Why do you want to do it? They are two different encoders.
> >>>>> eDP is primary display which in normal case should be bring up first if
> >>>>> DP is also presented.
> >>>> I do not like the concept of primary display. It is the user, who must
> >>>> decide which display is primary to him. I have seen people using just
> >>>> external monitors and ignoring built-in eDP completely.from
> >>>> Also, why does the bring up order matters here? What do you gain by
> >>>> bringing up eDP before the DP?
> >>> I should probably rephrase my question to be more clear. How does
> >>> changing the order of DP vs eDP bringup help you 'to fix screen
> >>> corruption'.
> >> it did fix the primary display correction issue if edp go first and i do
> >> not know the root cause yet.
> >>
> >> We are still investigating it.
> >>
> >> However I do think currently msm_dp_config sc7280_dp_cfg has issues need
> >> be addressed.
> >>
> > What issues exist with sc7280_dp_cfg? It looks correct to me.
>
>
> If we are going to bring up a new chipset with edp as primary only, i am
> not sure the below configuration will work?
>
> > static const struct msm_dp_config sc7280_dp_cfg = {
> >          .descs = (const struct msm_dp_desc[]) {
> >                  [MSM_DP_CONTROLLER_1] = { .io_start = 0x0aea0000, .connector_type = DRM_MODE_CONNECTOR_eDP, .wide_bus_en = true },
> >          },
> >          .num_descs = 1,
> > };

As I wrote in one of the comments, there is an issue with num_descs
being not obvious (in your example it should be 2, not 1). I thought
about dropping it and looping until the MSM_DP_CONTROLLER_COUNT, but
this would result in other kinds of hard-to-catch issues. Let me muse
about it.

-- 
With best wishes
Dmitry