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

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Message-ID: <20170704150902.GB10703@localhost>
Date:   Tue, 4 Jul 2017 17:09:02 +0200
From:   Pavel Machek <pavel@....cz>
To:     Tomi Valkeinen <tomi.valkeinen@...com>
Cc:     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,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [BISECTED, REGRESSION] v4.12-rc: omapdrm fails to probe on Nokia
 N900

Hi!

> >>>> Are you sure it doesn't probe? It fails the omapdss_stack_is_ready()
> >>>> check?
> >>>
> >>> It appears the reason was that I didn't have
> >>> CONFIG_DRM_OMAP_CONNECTOR_ANALOG_TV enabled.
> >>>
> >>> I think that's wrong. I don't own an analog TV, so why should I enable
> >>> such option to get device's built-in display working?
> >>
> >> Indeed. Unfortunately I don't have a solution for that.
> >>
> >> DRM doesn't support adding devices after probe. So at omapdrm probe time
> >> we have to decide which displays to use. In the dts file, n900 defines
> >> the lcd and analog tv. omapdrm sees those, and, of course, must wait
> >> until their respective drivers have probed. If you don't have the
> >> display driver enabled, it's never loaded and omapdrm never probes as it
> >> keeps waiting for those.
> > 
> > Could you at least print some kind of message early in the boot ("omapdrm
> > is waiting for drivers for display x and y")?
> 
> That could be quite spammy. omapdrm will defer probe if the displays are
> not present, and the deferred probing machinery will then cause a new
> omapdrm probe later. That can happen a lot of times before the drivers
> are there.

Well doing printk just once should not be a problem...?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html