Re: [PATCH 1/3] drm/radeon: Make CIK support in Radeon conditional (v2)

["Michel Dänzer" <michel-otUistvHUpPR7s880joybQ@public.gmane.org>]

On 10/04/17 09:56 AM, Michel Dänzer wrote:
> On 08/04/17 05:15 AM, Felix Kuehling wrote:
>> Advertise CIK PCI IDs only when they are not supported by amdgpu.
>> Use the CONFIG_DRM_AMDGPU_CIK to check so that a single option in
>> the kernel config keeps both drivers in sync.
>>
>> This is the simplest possible change. A more complete solution
>> may want to conditionally disable more CIK-specific code in the
>> Radeon driver.
>>
>> v2: Add CONFIG_DRM_RADEON_FORCE_CIK option
>>
>> Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
> 
> I don't think this is good enough a solution.

To elaborate, my main objection is that people who still want to be able
to use the radeon driver for CIK/SI GPUs with CONFIG_DRM_AMDGPU_CIK
enabled have to enable the new CONFIG_DRM_RADEON_FORCE_CIK/SI option,
and then they're merely back to square one, in the current situation
where it's not clearly defined which driver will end up being used for
such GPUs.


> CONFIG_DRM_AMDGPU_CIK/SI would then simply define which driver gets to
> drive CIK/SI GPUs by default.

To avoid the above, I'd say this should be the first step: Make
CONFIG_DRM_AMDGPU_CIK/SI define which driver will register for CIK/SI
GPUs by default. This does require some way to override it at runtime,
though. A simple initial solution for that might be
"force_cik"/"force_si" module parameters in both drivers. Setting
force_cik/si=1/0 would make the driver register for / not register for
CIK/SI GPUs.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer
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