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Date:   Tue, 5 Oct 2021 18:43:16 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <swboyd@...omium.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 v4 5/7] drm/msm/dp: Support up to 3 DP controllers

On Tue 05 Oct 17:43 PDT 2021, Stephen Boyd wrote:

> Quoting Bjorn Andersson (2021-10-05 16:13:21)
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> > index bdaf227f05dc..674cddfee5b0 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_display.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> > @@ -79,6 +79,8 @@ struct dp_display_private {
> >         char *name;
> >         int irq;
> >
> > +       unsigned int id;
> > +
> >         /* state variables */
> >         bool core_initialized;
> >         bool hpd_irq_on;
> > @@ -229,7 +231,7 @@ static int dp_display_bind(struct device *dev, struct device *master,
> >
> >         dp->dp_display.drm_dev = drm;
> >         priv = drm->dev_private;
> > -       priv->dp = &(dp->dp_display);
> > +       priv->dp[dp->id] = &(dp->dp_display);
> 
> Can we drop the extra parenthesis?
> 

Definitely.

> >
> >         rc = dp->parser->parse(dp->parser, dp->dp_display.connector_type);
> >         if (rc) {
> > @@ -269,7 +271,7 @@ static void dp_display_unbind(struct device *dev, struct device *master,
> >
> >         dp_power_client_deinit(dp->power);
> >         dp_aux_unregister(dp->aux);
> > -       priv->dp = NULL;
> > +       priv->dp[dp->id] = NULL;
> >  }
> >
> >  static const struct component_ops dp_display_comp_ops = {
> > @@ -1233,7 +1239,7 @@ static int dp_display_probe(struct platform_device *pdev)
> >         if (!dp)
> >                 return -ENOMEM;
> >
> > -       desc = dp_display_get_desc(pdev);
> > +       desc = dp_display_get_desc(pdev, &dp->id);
> 
> I'm sad that dp->id has to match the number in the SoC specific
> dpu_intf_cfg array in drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
> still. Is there any way we can avoid that? Also, notice how those arrays
> already have INTF_DP macros, which makes me think that it may be better
> to connect this to those arrays instead of making an msm_dp_desc
> structure and then make sure the 'type' member matches a connector
> type number. Otherwise this code is super fragile.
> 

I'm afraid I don't understand what you're proposing. Or which part you
consider fragile, the indices of the INTF_DP instances aren't going to
move around...

I have N instances of the DP driver that I need to match to N entries
from the platform specific intf array, I need some stable reference
between them. When I started this journey I figured I could rely on the
of_graph between the DPU and the interface controllers, but the values
used there today are just bogus, so that was a no go.

We can use whatever, as long as _dpu_kms_initialize_displayport() can
come up with an identifier to put in h_tile_instance[0] so that
dpu_encoder_setup_display() can find the relevant INTF.

Regards,
Bjorn

> >         if (!desc)
> >                 return -EINVAL;
> >

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