On 12/04/17 01:13 AM, Felix Kuehling wrote: > 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. Right. That said, CIK support in amdgpu seems to be getting pretty solid overall (and it's a requirement for Vulkan), so (something like) your latest patch will allow distros to keep radeon as the default for now, but make it easy for adventurous users to try out amdgpu. FWIW, some distros (at least openSuse AFAIK) are already enabling CONFIG_DRM_AMDGPU_CIK in their kernels, exposing their users to the gamble of which driver gets to drive their CIK GPUs. Thank you for getting the ball rolling on improving this situation! > 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. If nothing else, it'll allow us to give suggestions for easy workarounds in bug reports. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
