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

[Felix Kuehling]

On 17-04-10 09:39 PM, Michel Dänzer wrote:
> On 11/04/17 03:13 AM, Felix Kuehling wrote:
>> On 17-04-09 09:28 PM, Michel Dänzer wrote:
>>> 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 at 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.
>> So what's the usage model here? I think the situation that both AMDGPU
>> and Radeon support CIK is for developers only. "Normal end users" would
>> never be in this situation.
> I agree in the long term, but for now, there's still too many bugs which
> force users to use one or the other driver. Since this patch would
> require distros to choose one driver for all of their users, with no way
> to override at runtime, it would probably result in bad user experiences
> and/or a support nightmare at least in the short term.

Right now the only sane configuration that a distro can choose is to
support CIK with radeon and not build CIK support into amdgpu. That
choice will still be available. So nothing changes for a risk-averse
distribution.

If a distribution's choice does not work for all users, and end users
have to change the preference at runtime, that's already a bad user
experience. Just having the runtime option available doesn't make it a
better user experience, because most user won't know that there is a
choice and won't know that their issues can be fixed that way.

Regards,
  Felix