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From: Alex Deucher <alexdeucher@gmail.com>
To: Eric Anholt <eric@anholt.net>
Cc: Daniel Vetter <daniel@ffwll.ch>,
	Mark Rutland <mark.rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 2/3] drm/vc4: Don't try to initialize FBDEV if we're only bound to V3D.
Date: Mon, 24 Apr 2017 10:26:45 -0400	[thread overview]
Message-ID: <CADnq5_OEX2kzLJ5ABfBs6fZnmhFmJAPbg1XjJWx9Pt_pu=bTEA@mail.gmail.com> (raw)
In-Reply-To: <87wpadtlsl.fsf@eliezer.anholt.net>

On Fri, Apr 21, 2017 at 6:53 PM, Eric Anholt <eric@anholt.net> wrote:
> Daniel Vetter <daniel@ffwll.ch> writes:
>
>> On Wed, Apr 19, 2017 at 7:55 PM, Eric Anholt <eric@anholt.net> wrote:
>>> Daniel Vetter <daniel@ffwll.ch> writes:
>>>> On Tue, Apr 18, 2017 at 9:11 PM, Eric Anholt <eric@anholt.net> wrote:
>>>>> The FBDEV initialization would throw an error in dmesg, when we just
>>>>> want to silently not initialize fbdev on a V3D-only VC4 instance.
>>>>>
>>>>> Signed-off-by: Eric Anholt <eric@anholt.net>
>>>>
>>>> Hm, this shouldn't be an error really, you might want to hotplug more
>>>> connectors later on. What exactly complains?
>>>
>>> drm_fb_helper_init() throws an error if the passed in connector count is
>>> 0, so drm_fb_cma_helper() printks an error.
>>
>> Oh, _that_ thing. The error in there is correct, but (almost) everyone
>> gets this parameter wrong. This isn't the max number of connectors the
>> fb helper will light up, but just the max number of connectors _per_
>> crtc when driving in hw clone mode. There's two problems with that:
>> - fb helpers don't support hw clone mode, we select 1:1 crtcs for each
>> active connector
>> - I mentioned that everyone gets this wrong?
>>
>> If you're moderately bored it'd be great to nuke the max_connector
>> argument from drm_fb_helper_init, and hard-code it to 1 (with a big
>> comment explaining that this needs to be changed, probably with
>> dynamic reallocation, once someone gets around to implementing hw
>> clone mode).
>>
>> If you're less bored, just hardcode this to 1 in vc4 and done. Plus a
>> TODO.rst entry would be great in that case.
>
> If I'm driving a GPU with no display subsystem at all, it seems like I
> shouldn't initialize fbdev for it, right?

That's what we do for radeon/amdgpu on hw without display blocks.

Alex

  reply	other threads:[~2017-04-24 14:27 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-18 19:11 [PATCH 1/3] drm/vc4: Turn the V3D clock on at runtime Eric Anholt
2017-04-18 19:11 ` [PATCH 2/3] drm/vc4: Don't try to initialize FBDEV if we're only bound to V3D Eric Anholt
2017-04-19  4:59   ` Daniel Vetter
2017-04-19 17:55     ` Eric Anholt
2017-04-19 19:36       ` Daniel Vetter
2017-04-21 22:53         ` Eric Anholt
2017-04-24 14:26           ` Alex Deucher [this message]
2017-05-02  8:16             ` Daniel Vetter
2017-04-18 19:11 ` [PATCH 3/3] drm/vc4: Add specific compatible strings for Cygnus Eric Anholt
2017-04-20 20:33   ` Rob Herring
2017-04-18 19:23 ` [PATCH 1/3] drm/vc4: Turn the V3D clock on at runtime Eric Anholt
2017-04-18 23:38 ` [PATCH 1/3 v2] " Eric Anholt
2017-04-18 23:48   ` Florian Fainelli
2017-04-19  0:02     ` Eric Anholt
2017-04-19  0:02     ` Eric Anholt
2017-04-24 20:12     ` [PATCH 1/3 v3] " Eric Anholt
2017-04-28 18:29       ` Rob Herring
2017-04-28 21:41         ` Eric Anholt

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