linux-kernel - Re: [PATCH v3] drm/gma500: depend on framebuffer

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Message-ID: <09cc1d94-d25e-4fbd-bb95-03d0135cf818@suse.de>
Date:   Thu, 21 Apr 2022 15:20:55 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        Javier Martinez Canillas <javierm@...hat.com>
Cc:     David Airlie <airlied@...ux.ie>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        James Hilliard <james.hilliard1@...il.com>
Subject: Re: [PATCH v3] drm/gma500: depend on framebuffer

Hi

Am 21.04.22 um 14:54 schrieb Patrik Jakobsson:
> On Thu, Apr 21, 2022 at 2:47 PM Javier Martinez Canillas
> <javierm@...hat.com> wrote:
>>
>> Hello Patrik,
>>
>> On 4/21/22 14:39, Patrik Jakobsson wrote:
>>> On Thu, Apr 21, 2022 at 1:49 PM Thomas Zimmermann <tzimmermann@...e.de> wrote:
>>>>
>>>> Hi
>>>>
>>>> Am 09.04.22 um 06:23 schrieb James Hilliard:
>>>>> Select the efi framebuffer if efi is enabled.
>>>>>
>>>>> This appears to be needed for video output to function correctly.
>>>>>
>>>>> Signed-off-by: James Hilliard <james.hilliard1@...il.com>
>>>>> ---
>>>>> Changes v2 -> v3:
>>>>>     - select EFI_FB instead of depending on it
>>>>> Changes v1 -> v2:
>>>>>     - use depends instead of select
>>>>> ---
>>>>>    drivers/gpu/drm/gma500/Kconfig | 2 ++
>>>>>    1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/gma500/Kconfig b/drivers/gpu/drm/gma500/Kconfig
>>>>> index 0cff20265f97..a422fa84d53b 100644
>>>>> --- a/drivers/gpu/drm/gma500/Kconfig
>>>>> +++ b/drivers/gpu/drm/gma500/Kconfig
>>>>> @@ -2,11 +2,13 @@
>>>>>    config DRM_GMA500
>>>>>        tristate "Intel GMA500/600/3600/3650 KMS Framebuffer"
>>>>>        depends on DRM && PCI && X86 && MMU
>>>>> +     depends on FB
>>>>
>>>> Why do we need FB here? Framebuffer support should be hidden by DRM's
>>>> fbdev helpers.
>>>
>>> It is not needed but gives him video output since it enables the drm
>>> fbdev emulation.
>>>
>>
>> I'm not sure to understand this. Shouldn't depend on DRM_FBDEV_EMULATION then?

It has to be selected separately in .config.

James, make sure you have DRM_FBDEV_EMULATION enabled in your kernel's 
.config file if you want a console. however, Weston should work without 
it.  How do you start weston without a console?

> 
> No, it shouldn't depend on any FBDEV stuff since it's not actually
> required. It just happens to help in this case since weston + fbdev
> backend works but not weston with drm backend (or whatever config
> James have set).
> 
>>
>>> I looked some more at the logs and it seems weston doesn't work on his
>>> system without the fbdev backend. So the question is why weston isn't
>>> working without fbdev? Perhaps this is just a Weston configuration
>>> issue?
>>>
>>
>> But is weston using the fbdev emulated by DRM or the one registered by
>> efifb? I thought that the latter from what was mentioned in this thread.
> 
> It's using drm fbdev emulation with gma500 so EFIFB has nothing to do
> with this. I believe it was just simply incorrectly reported. If I'm
> correct then "depends on FB" is what makes video output work for
> James.

There's an fbdev backend for weston, but the provided logs don't look as 
if it's using this.  Maybe the connector's modes are never probed 
correctly without fbdev.

James, could you provide a logfile for weston? (i.e., 'weston 
--log=weston.txt').

Best regards
Thomas

> 
>>
>> --
>> Best regards,
>>
>> Javier Martinez Canillas
>> Linux Engineering
>> Red Hat
>>

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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