linux-kernel - Re: [PATCH v3] drm/bridge: panel: Add a device link between drm device and panel device

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Message-ID: <CACRpkdYPDi+TYj4Y89+iLKa__oFTuMKCPDB7UrVThEGd=6H3qw@mail.gmail.com>
Date:   Wed, 22 Nov 2023 14:58:30 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Ying Liu <victor.liu@....com>
Cc:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "andrzej.hajda@...el.com" <andrzej.hajda@...el.com>,
        "neil.armstrong@...aro.org" <neil.armstrong@...aro.org>,
        "rfoss@...nel.org" <rfoss@...nel.org>,
        "Laurent.pinchart@...asonboard.com" 
        <Laurent.pinchart@...asonboard.com>,
        "jonas@...boo.se" <jonas@...boo.se>,
        "jernej.skrabec@...il.com" <jernej.skrabec@...il.com>,
        "airlied@...il.com" <airlied@...il.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v3] drm/bridge: panel: Add a device link between drm
 device and panel device

Hi Ying,

On Mon, Nov 20, 2023 at 11:08 AM Ying Liu <victor.liu@....com> wrote:

[Me]
> > > v2->v3:
> > > * Improve commit message s/swapped/reversed/.
> >
> > This patch causes a regression in the Ux500 MCDE
> > drivers/gpu/drm/mcde/* driver with the nt35510 panel
> > drivers/gpu/drm/panel/panel-novatek-nt35510.c
> > my dmesg looks like this:
(...)
> Sorry for the breakage and a bit late response(I'm a bit busy with internal
> things).
>
> I think device_link_add() fails because a0351000.dsi.0 already depends
> on a0350000.mcde.  Can you confirm that device_link_add() returns NULL
> right after it calls device_is_dependent()?
>
> Does this patch fix the issue?

Yep it works!

You missed one device_link_del() instance on the errorpath.

Tested-by: Linus Walleij <linus.walleij@...aro.org>

Can you send it as a proper patch?

Yours,
Linus Walleij