linux-kernel - Re: [PATCH 11/11] video/aperture: Only remove sysfb on the default vga pci device

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Message-ID: <7b00e592-345f-4dd5-3452-7f6f70fc608a@suse.de>
Date:   Thu, 12 Jan 2023 08:55:46 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Aaron Plattner <aplattner@...dia.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Helge Deller <deller@....de>, Sam Ravnborg <sam@...nborg.org>,
        Alex Deucher <alexander.deucher@....com>,
        stable@...r.kernel.org
Subject: Re: [PATCH 11/11] video/aperture: Only remove sysfb on the default
 vga pci device

Hi

Am 11.01.23 um 20:21 schrieb Aaron Plattner:
> On 1/11/23 8:58 AM, Javier Martinez Canillas wrote:
>> Hello Daniel,
>>
>> On 1/11/23 16:41, Daniel Vetter wrote:
>>> This fixes a regression introduced by ee7a69aa38d8 ("fbdev: Disable
>>> sysfb device registration when removing conflicting FBs"), where we
>>> remove the sysfb when loading a driver for an unrelated pci device,
>>> resulting in the user loosing their efifb console or similar.
>>>
>>> Note that in practice this only is a problem with the nvidia blob,
>>> because that's the only gpu driver people might install which does not
>>> come with an fbdev driver of it's own. For everyone else the real gpu
>>> driver will restor a working console.
>>
>> restore
>>
>>>
>>> Also note that in the referenced bug there's confusion that this same
>>> bug also happens on amdgpu. But that was just another amdgpu specific
>>> regression, which just happened to happen at roughly the same time and
>>> with the same user-observable symptons. That bug is fixed now, see
>>
>> symptoms
>>
>>> https://bugzilla.kernel.org/show_bug.cgi?id=216331#c15
>>>
>>> For the above reasons the cc: stable is just notionally, this patch
>>> will need a backport and that's up to nvidia if they care enough.
>>>
>>
>> Maybe adding a Fixes: ee7a69aa38d8 tag here too ?
>>
>>> References: https://bugzilla.kernel.org/show_bug.cgi?id=216303#c28
>>> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
>>> Cc: Aaron Plattner <aplattner@...dia.com>
>>> Cc: Javier Martinez Canillas <javierm@...hat.com>
>>> Cc: Thomas Zimmermann <tzimmermann@...e.de>
>>> Cc: Helge Deller <deller@....de>
>>> Cc: Sam Ravnborg <sam@...nborg.org>
>>> Cc: Alex Deucher <alexander.deucher@....com>
>>> Cc: <stable@...r.kernel.org> # v5.19+ (if someone else does the 
>>> backport)
>>> ---
>>>   drivers/video/aperture.c | 7 ++++---
>>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
>>> index ba565515480d..a1821d369bb1 100644
>>> --- a/drivers/video/aperture.c
>>> +++ b/drivers/video/aperture.c
>>> @@ -321,15 +321,16 @@ int 
>>> aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const 
>>> char *na
>>>       primary = pdev == vga_default_device();
>>> +    if (primary)
>>> +        sysfb_disable();
>>> +
>>>       for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
>>>           if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
>>>               continue;
>>>           base = pci_resource_start(pdev, bar);
>>>           size = pci_resource_len(pdev, bar);
>>> -        ret = aperture_remove_conflicting_devices(base, size, name);
>>> -        if (ret)
>>> -            return ret;
>>> +        aperture_detach_devices(base, size);
>>
>> Maybe mention in the commit message that you are doing this change, 
>> something like:
>>
>> "Instead of calling aperture_remove_conflicting_devices() to remove 
>> the conflicting
>> devices, just call to aperture_detach_devices() to detach the device 
>> that matches
>> the same PCI BAR / aperture range. Since the former is just a wrapper 
>> of the latter
>> plus a sysfb_disable() call, and now that's done in this function but 
>> only for the
>> primary devices"
>>
>> Patch looks good to me:
>>
>> Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>
> 
> Thanks Daniel and Javier!
> 
> I wasn't able to reproduce the original problem on my hybrid laptop 
> since it refuses to boot with the console on an external display, but I 
> was able to reproduce it by switching the configuration around: booting 
> with i915.modeset=0 and with an experimental version of nvidia-drm that 
> registers a framebuffer console. I verified that loading nvidia-drm 

Thank you for testing.

One thing I'd like to note is that using DRM's fbdev emulation is the 
correct way to support a console. Nvidia-drm's current approach of 
utilizing efifb is fragile and requires workarounds from distributions 
(at least here at SUSE). Steps towards fbdev emulation are much appreciated.

Best regards
Thomas

> breaks the efi-firmware framebuffer on Intel on Arch's 
> linux-6.1.4-arch1-1 kernel and that applying this patch series fixes it. So
> 
> Tested-by: Aaron Plattner <aplattner@...dia.com>
> 
> FWIW, the bug ought to be reproducible with i915.modeset=0 + any other 
> drm driver that registers a framebuffer.
> 
> -- Aaron

-- 
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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