linux-kernel - Re: [REGRESSION] "drm: convert drivers to use drm_of_find_panel_or

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Date:   Thu, 4 May 2017 17:42:23 -0500
From:   Rob Herring <robh@...nel.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     Archit Taneja <architt@...eaurora.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Sean Paul <seanpaul@...omium.org>,
        Dave Airlie <airlied@...il.com>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [REGRESSION] "drm: convert drivers to use drm_of_find_panel_or_bridge"
 breaks graphics on hikey

On Thu, May 4, 2017 at 5:33 PM, John Stultz <john.stultz@...aro.org> wrote:
> Hey folks,
>   Testing mainline with HiKey, I noticed graphics was no longer
> properly initializing. I don't seem to get much useful info in the way
> of errors, its just the kirin drm driver doesn't seem to
> initialize/bind.
>
> Digging through the recent changes I landed on ebc944613567 ("drm:
> convert drivers to use drm_of_find_panel_or_bridge").  And reverting
> that patch (which doesn't revert cleanly, but cleanly enough for me to
> test my device), seems to resolve the issue.
>
> I've not been able to root cause the problem, but I wanted to bring it
> up quickly here, as folks might figure out the error faster then I
> can.

Looking at the change to HiSilicon code:

-       endpoint = of_graph_get_endpoint_by_regs(np, 1, -1);
[...]
+       ret = drm_of_find_panel_or_bridge(np, 0, 0, NULL, &dsi->bridge);

This should be (1,0) rather than (0,0) for (port,endpoint).

Rob