linux-kernel - Re: [BISECTED, REGRESSION] v4.12-rc: omapdrm fails to probe on Nokia N900

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Message-ID: <f7697b9f-b506-bf18-43f9-921ed7f27607@ti.com>
Date:   Thu, 15 Jun 2017 09:51:06 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Aaro Koskinen <aaro.koskinen@....fi>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Tony Lindgren <tony@...mide.com>,
        <linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>
Subject: Re: [BISECTED, REGRESSION] v4.12-rc: omapdrm fails to probe on Nokia
 N900

On 15/06/17 01:11, Aaro Koskinen wrote:
> Hi,
> 
> When booting v4.12-rc5 on Nokia N900, omapdrm fails to probe and there
> is no display.

Are you sure it doesn't probe? It fails the omapdss_stack_is_ready()
check? If that's the case then this is easier to debug.

> Bisected to:
> 
> a09d2bc1503508c17ef3a71c6b1905e3660f3029 is the first bad commit
> commit a09d2bc1503508c17ef3a71c6b1905e3660f3029
> Author: Peter Ujfalusi <peter.ujfalusi@...com>
> Date:   Tue May 3 22:08:01 2016 +0300
> 
>     drm/omap: Use omapdss_stack_is_ready() to check that the display stack is up
>     
>     Instead of 'guessing' based on aliases of the status of the DSS drivers,
>     use the new interface to check that all needed drivers are loaded.
>     In this way we can be sure that all needed drivers are loaded so it is
>     safe to continue the probing of omapdrm.
>     This method will allow the omapdrm to be probed 'headless', without
>     outputs.
>     
>     Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
>     Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
> 
> Reverting the commit seems to fix the issue.

This is probably "fixed" by adding the display aliases into the n900 dts
file. The aliases should not really be required, although they are
recommended. Without the aliases the order of the displays is random,
and n900 could end up using tv-out as the first display. But even then,
the displays should still work.

 Tomi



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