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

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Message-ID: <c3ed82bc-cc15-7d0d-8968-b71ad3d4003f@suse.de>
Date:   Thu, 21 Apr 2022 20:23:33 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     James Hilliard <james.hilliard1@...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>
Subject: Re: [PATCH v3] drm/gma500: depend on framebuffer

Hi

Am 21.04.22 um 20:22 schrieb Thomas Zimmermann:
> Hi
> 
> Am 21.04.22 um 19:39 schrieb James Hilliard:
>> On Thu, Apr 21, 2022 at 8:22 AM Javier Martinez Canillas
>> <javierm@...hat.com> wrote:
>>>
>>> On 4/21/22 14:54, Patrik Jakobsson wrote:
>>>> On Thu, Apr 21, 2022 at 2:47 PM Javier Martinez Canillas
>>>> <javierm@...hat.com> wrote:
>>>
>>> [snip]
>>>
>>>>>>>> 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?
>>>>
>>>> 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 see. Then the correct approach for them would be to just enable 
>>> CONFIG_FB
>>> and DRM_FBDEV_EMULATION in their kernel config, rather than making 
>>> this to
>>> depend on anything FB related as you said.
>>
>> Yeah, so it looks like CONFIG_FB_EFI is not needed but
>> CONFIG_DRM_FBDEV_EMULATION is, I think I just assumed efifb
>> was what was needed based on the kernel logs.
>>
>> This does not work:
>> CONFIG_FB enabled
>> CONFIG_DRM_FBDEV_EMULATION disabled
>>
>> This works:
>> CONFIG_FB enabled
>> CONFIG_DRM_FBDEV_EMULATION enabled
>>
>>>
>>>>
>>>>>
>>>>>> 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.
>>>>
>>>
>>> Got it. Thanks for the clarification.
>>
>> Here's my weston.ini:
>> [core]
>> shell=kiosk-shell.so
>> modules=systemd-notify.so
>> backend=drm-backend.so
>> idle-time=0
>> require-input=false
>> use-pixman=true
>>
>> [shell]
>> locking=false
>> cursor-theme=Obsidian
>> panel-position=none
>>
>> [output]
>> name=DVI-D-1
>> transform=rotate-270
>>
>> [output]
>> name=DP-2
>> mode=off
>>
>> [output]
>> name=LVDS-1
>> mode=off
> 
> You mentioned that you want to use HDMI, but it's not configured here. 
> Is that intentionally?

Nevermind. I just saw that DVI-D-1 is the HDMI port. (why?)

> 
> Best regards
> Thomas
> 
>>
>> [libinput]
>> touchscreen_calibrator=true
>>
>>>
>>> -- 
>>> 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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