linux-kernel - Re: [Freedreno] [PATCH 3/3] drm/msm/dsi: make sure we have panel or bridge earlier

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Date:   Tue, 2 Jul 2019 15:29:47 -0600
From:   Jeffrey Hugo <jeffrey.l.hugo@...il.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Rob Clark <robdclark@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        MSM <linux-arm-msm@...r.kernel.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        lkml <linux-kernel@...r.kernel.org>, Sean Paul <sean@...rly.run>,
        Sibi Sankar <sibis@...eaurora.org>,
        Daniel Vetter <daniel@...ll.ch>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Chandan Uddaraju <chandanu@...eaurora.org>
Subject: Re: [Freedreno] [PATCH 3/3] drm/msm/dsi: make sure we have panel or
 bridge earlier

On Tue, Jul 2, 2019 at 2:30 PM Jeffrey Hugo <jeffrey.l.hugo@...il.com> wrote:
>
> On Sun, Jun 30, 2019 at 7:16 AM Rob Clark <robdclark@...il.com> wrote:
> > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > @@ -1824,6 +1824,20 @@ int msm_dsi_host_init(struct msm_dsi *msm_dsi)
> >                 goto fail;
> >         }
> >
> > +       /*
> > +        * Make sure we have panel or bridge early, before we start
> > +        * touching the hw.  If bootloader enabled the display, we
> > +        * want to be sure to keep it running until the bridge/panel
> > +        * is probed and we are all ready to go.  Otherwise we'll
> > +        * kill the display and then -EPROBE_DEFER
> > +        */
> > +       if (IS_ERR(of_drm_find_panel(msm_host->device_node)) &&
> > +                       !of_drm_find_bridge(msm_host->device_node)) {
> > +               pr_err("%s: no panel or bridge yet\n", __func__);
>
> pr_err() doesn't seem right for a probe defer condition.  pr_dbg?
>
> > +               return -EPROBE_DEFER;
> > +       }
> > +
> > +
>
> Tested-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>
> Reviewed-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>

Actually, I'm sorry, I'm now NACKing this.

Turns out this prevents the panel/bridge from ever probing if its a
child node of the dsi device, since mipi_dsi_host_register() is never
called.

This probably works for you on the c630 because the bridge hangs off
the i2c bus.