linux-kernel - Re: [PATCH v3 3/5] drm/msm/dp: Support up to 3 DP controllers

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Date:   Mon, 4 Oct 2021 21:17:53 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Abhinav Kumar <abhinavk@...eaurora.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Kalyan Thota <kalyan_t@...eaurora.org>,
        Kuogee Hsieh <khsieh@...eaurora.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/5] drm/msm/dp: Support up to 3 DP controllers

Quoting Bjorn Andersson (2021-10-04 18:15:20)
> On Mon 04 Oct 17:58 PDT 2021, Stephen Boyd wrote:
>
> > Quoting Bjorn Andersson (2021-10-01 11:00:56)
> > > Based on the removal of the g_dp_display and the movement of the
> > > priv->dp lookup into the DP code it's now possible to have multiple
> > > DP instances.
> > >
> > > In line with the other controllers in the MSM driver, introduce a
> > > per-compatible list of base addresses which is used to resolve the
> > > "instance id" for the given DP controller. This instance id is used as
> > > index in the priv->dp[] array.
> > >
> > > Then extend the initialization code to initialize struct drm_encoder for
> > > each of the registered priv->dp[] and update the logic for associating
> > > each struct msm_dp with the struct dpu_encoder_virt.
> > >
> > > Lastly, bump the number of struct msm_dp instances carries by priv->dp
> > > to 3, the currently known maximum number of controllers found in a
> > > Qualcomm SoC.
> > >
> > > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > ---
> >
> > Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> >
> > Some nits below.
> >
> > >
> > > Changes since v2:
> > > - Added MSM_DRM_DP_COUNT to link the two 3s
> > > - Moved NULL check for msm_dp_debugfs_init() to the call site
> > > - Made struct dp_display_private->id unsigned
> > >
> > > I also implemented added connector_type to each of the DP instances and
> > > propagated this to dp_drm_connector_init() but later dropped this again per
> > > Doug's suggestion that we'll base this on the presence/absence of a associated
> > > drm bridge or panel.
> >
> > Sad but OK. We can take up that topic in another patch.
> >
>
> So you don't agree with the solution from sn65dsi86?
>
> The only reason I haven't yet send this other patch is the of_graph
> thing Doug an I are discussing on the RFC. But if we agree to base this
> on compatible we could decide to look only for panels for the edp
> instances and avoid that problem...
>
> We would however never be able to describe the USB-less DP instance with
> a panel explicitly described in DT going that route.

I'll reply on that thread.

>
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > > index f655adbc2421..875b07e7183d 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > > @@ -203,8 +204,10 @@ static int dpu_kms_debugfs_init(struct msm_kms *kms, struct drm_minor *minor)
> > >         dpu_debugfs_vbif_init(dpu_kms, entry);
> > >         dpu_debugfs_core_irq_init(dpu_kms, entry);
> > >
> > > -       if (priv->dp)
> > > -               msm_dp_debugfs_init(priv->dp, minor);
> > > +       for (i = 0; i < ARRAY_SIZE(priv->dp); i++) {
> > > +               if (priv->dp[i])
> > > +                       msm_dp_debugfs_init(priv->dp[i], minor);
> >
> > This seems to cause a bunch of debugfs warnings when there are multiple
> > nodes created with the same name.
> >
>
> Yes, that's true. I have a half-baked follow up that attempts to create
> instance-specific debugfs directories. Can we take that in a follow up?

Sure.

>
> > > +       }
> > >
> > >         return dpu_core_perf_debugfs_init(dpu_kms, entry);
> > >  }
> > > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > > index 5d3ee5ef07c2..ff3477474c5d 100644
> > > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > > @@ -1180,10 +1192,31 @@ int dp_display_request_irq(struct msm_dp *dp_display)
> > >         return 0;
> > >  }
> > >
> > > +static int dp_display_find_id(struct platform_device *pdev)
> > > +{
> > > +       const struct msm_dp_config *cfg = of_device_get_match_data(&pdev->dev);
> > > +       struct resource *res;
> > > +       int i;
> > > +
> > > +
> >
> > Nitpick: Remove a newline here.
> >
> > > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > +       if (!res)
> > > +               return -EINVAL;
> > > +
> > > +       for (i = 0; i < cfg->num_descs; i++) {
> > > +               if (cfg->io_start[i] == res->start)
> > > +                       return i;
> > > +       }
> >
> > Nitpick: Drop braces on single line if inside for loop.
> >
>
> Not when the loop spans multiple lines?

Kernel style is to remove braces from single "statement" for loops where
in this case the statement is the if condition.

>
> > > +
> > > +       dev_err(&pdev->dev, "unknown displayport instance\n");
> > > +       return -EINVAL;
> > > +}
> > > +