linux-kernel - Re: [PATCH AUTOSEL 6.14 107/642] drm/amdgpu: adjust drm_firmware_drivers

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Message-ID: <43542c17-379c-40c3-ab18-4646c0e70698@suse.de>
Date: Thu, 21 Aug 2025 11:34:02 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Cc: Alex Deucher <alexander.deucher@....com>,
 Kent Russell <kent.russell@....com>, christian.koenig@....com,
 airlied@...il.com, simona@...ll.ch, lijo.lazar@....com,
 mario.limonciello@....com, rajneesh.bhardwaj@....com, kenneth.feng@....com,
 Ramesh.Errabolu@....com, amd-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH AUTOSEL 6.14 107/642] drm/amdgpu: adjust
 drm_firmware_drivers_only() handling



Am 21.08.25 um 11:32 schrieb Thomas Zimmermann:
> Hi
>
> Am 06.05.25 um 00:05 schrieb Sasha Levin:
>> From: Alex Deucher <alexander.deucher@....com>
>>
>> [ Upstream commit e00e5c223878a60e391e5422d173c3382d378f87 ]
>>
>> Move to probe so we can check the PCI device type and
>> only apply the drm_firmware_drivers_only() check for
>> PCI DISPLAY classes.  Also add a module parameter to
>> override the nomodeset kernel parameter as a workaround
>> for platforms that have this hardcoded on their kernel
>> command lines.
>
> I just came across this patch because it got backported into various 
> older releases. It was part of the series at [1]. From the cover letter:

[1] 
https://lore.kernel.org/all/20250314010152.1503510-1-alexander.deucher@amd.com/

>
> >>>
>
> There are a number of systems and cloud providers out there
> that have nomodeset hardcoded in their kernel parameters
> to block nouveau for the nvidia driver.  This prevents the
> amdgpu driver from loading. Unfortunately the end user cannot
> easily change this.  The preferred way to block modules from
> loading is to use modprobe.blacklist=<driver>.  That is what
> providers should be using to block specific drivers.
>
> Drop the check to allow the driver to load even when nomodeset
> is specified on the kernel command line.
>
> <<<
>
> Why was that series never on dri-devel?
>
> Why is this necessary in the upstream kernel? It works around a 
> problem with the user's configuration. The series' cover letter 
> already states the correct solution.
>
> Firmware-only parameters affect all drivers; why not try for a common 
> solution? At least the test against the PCI class appears useful in 
> the common case.
>
> Best regards
> Thomas
>
>
>>
>> Reviewed-by: Kent Russell <kent.russell@....com>
>> Signed-off-by: Alex Deucher <alexander.deucher@....com>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> index f2d77bc04e4a9..7246c54bd2bbf 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> @@ -173,6 +173,7 @@ uint amdgpu_sdma_phase_quantum = 32;
>>   char *amdgpu_disable_cu;
>>   char *amdgpu_virtual_display;
>>   bool enforce_isolation;
>> +int amdgpu_modeset = -1;
>>     /* Specifies the default granularity for SVM, used in buffer
>>    * migration and restoration of backing memory when handling
>> @@ -1033,6 +1034,13 @@ module_param_named(user_partt_mode, 
>> amdgpu_user_partt_mode, uint, 0444);
>>   module_param(enforce_isolation, bool, 0444);
>>   MODULE_PARM_DESC(enforce_isolation, "enforce process isolation 
>> between graphics and compute . enforce_isolation = on");
>>   +/**
>> + * DOC: modeset (int)
>> + * Override nomodeset (1 = override, -1 = auto). The default is -1 
>> (auto).
>> + */
>> +MODULE_PARM_DESC(modeset, "Override nomodeset (1 = enable, -1 = 
>> auto)");
>> +module_param_named(modeset, amdgpu_modeset, int, 0444);
>> +
>>   /**
>>    * DOC: seamless (int)
>>    * Seamless boot will keep the image on the screen during the boot 
>> process.
>> @@ -2244,6 +2252,12 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
>>       int ret, retry = 0, i;
>>       bool supports_atomic = false;
>>   +    if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA ||
>> +        (pdev->class >> 8) == PCI_CLASS_DISPLAY_OTHER) {
>> +        if (drm_firmware_drivers_only() && amdgpu_modeset == -1)
>> +            return -EINVAL;
>> +    }
>> +
>>       /* skip devices which are owned by radeon */
>>       for (i = 0; i < ARRAY_SIZE(amdgpu_unsupported_pciidlist); i++) {
>>           if (amdgpu_unsupported_pciidlist[i] == pdev->device)
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)