Am 03.04.2018 um 10:36 schrieb Michel Dänzer: > On 2018-04-01 07:45 PM, Ilia Mirkin wrote: >> On Sun, Apr 1, 2018 at 1:39 PM, Christian König >> <christian.koenig at amd.com> wrote: >>> Am 30.03.2018 um 22:45 schrieb Takashi Iwai: >>>> amdgpu driver lacks of modeset module option other drm drivers provide >>>> for enforcing or disabling the driver load. Interestingly, the >>>> amdgpu_mode variable declaration is already found in the header file, >>>> but the actual implementation seems to have been forgotten. >>>> >>>> This patch adds the missing piece. >>> >>> NAK, modesetting is mandatory for amdgpu and we should probably remove the >>> option to disable it from other DRM drivers without UMS support as well >>> (pretty much all of them now). >>> >>> If you want to prevent a driver from loading I think the correct way to do >>> so is to give modprobe.blacklist=amdgpu on the kernel commandline. >>> >>> That would remove the possibility to prevent the driver from loading when it >>> is compiled in, but I don't see much of a problem with that. >> Having a way to kill the graphics driver is a very useful debugging >> tool, and also a quick and easy way to get out of an unpleasant >> situation where graphics are messed up / system hangs / etc. The >> modprobe blacklist kernel arg only works in certain environments (and >> only if it's a module). > Building amdgpu into the kernel isn't feasible for a generic kernel such > as a distro one, because it would require including all microcode into > the kernel as well (12M right now, and growing). > > If a user decides to build amdgpu into their custom kernel and runs into > trouble due to that, that's "doctor, it hurts if I do this" territory. Correct, but I agree that even in this situation it would be very helpful to prevent the gfx drivers from loading and fallback to efifb/vesafd (or whatever the platform provides). It's just that the "nomodeset" and "amdgpu.modeset=0" options are really not well named for this task. Christian.
