On Tue, Apr 03, 2018 at 05:02:35PM +0200, Daniel Vetter wrote: > On Tue, Apr 03, 2018 at 05:06:03PM +0300, Ville Syrjälä wrote: > > On Tue, Apr 03, 2018 at 03:47:57PM +0200, Michel Dänzer wrote: > > > On 2018-04-03 03:39 PM, Ilia Mirkin wrote: > > > > On Tue, Apr 3, 2018 at 9:32 AM, Michel Dänzer <michel at daenzer.net> wrote: > > > >> On 2018-04-03 03:26 PM, Ilia Mirkin wrote: > > > >>> On Tue, Apr 3, 2018 at 5:29 AM, Daniel Vetter <daniel at ffwll.ch> wrote: > > > >>>> On Sun, Apr 01, 2018 at 10:12:10PM +0200, Christian König wrote: > > > >>>>> Am 01.04.2018 um 20:21 schrieb Takashi Iwai: > > > >>>>>> On Sun, 01 Apr 2018 19:58:11 +0200, > > > >>>>>> Christian K6nig wrote: > > > >>>>>>> Am 01.04.2018 um 19:45 schrieb Ilia Mirkin: > > > >>>>>>>> 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). > > > >>>>>>>> > > > >>>>>>>> Every other DRM driver has this and this is a well-documented > > > >>>>>>>> workaround for "graphics are messed up when I install linux", why not > > > >>>>>>>> allow a uniform experience for the end users who are just trying to > > > >>>>>>>> get their systems up and running? > > > >>>>>>> Because it is not well documented and repeated over and over again in > > > >>>>>>> drivers. > > > >>>>>>> > > > >>>>>>> The problem is that people don't realized that the driver isn't loaded > > > >>>>>>> at all without the modeset=0 module option and demand fixing the > > > >>>>>>> resulting bad performance without modesetting. > > > >>>>>> Hm, I don't get it. What this options has to do with performance for > > > >>>>>> a KMS-only driver...? > > > >>>>> > > > >>>>> Well exactly that's the point, nothing. > > > >>>>> > > > >>>>> The problem is that the option name is confusing to the end user because the > > > >>>>> expectation is that "nomodeset" just means that they only can't change the > > > >>>>> display mode. > > > >>>>> > > > >>>>> Some (unfortunately quite a lot) people don't realize that for KMS drivers > > > >>>>> this means that the driver isn't even loaded and they also don't get any > > > >>>>> acceleration. > > > >>>>> > > > >>>>> We had to explain that numerous times now. I think it would be best to give > > > >>>>> the option a more meaningful name. > > > >>>> > > > >>>> Yeah, agreed with Christian. If we want a generic "pls disable all gfx > > > >>>> accel" knob then probably best to put that into the drm core. And just > > > >>>> outright fail loading the drm core if that happens, which will prevent all > > > >>>> gfx drivers from loading. > > > >>>> > > > >>>> That likely means a hole bunch of stuff won't work (usually sound keels > > > >>>> over too), but that's what you get for this. Only disabling modesetting > > > >>>> without disabling the entire driver doesn't work (never has, except for > > > >>>> this UMS+GEM combo only i915 support, and not for long). > > > >>>> > > > >>>> And once we have that knob, probably best to phase out all the per-driver > > > >>>> options. > > > >>> > > > >>> Another use-case that the per-driver disables enable is "i915 works > > > >>> but nouveau is broken due to crazy ACPI / PCIe PM / whatever". It > > > >>> seems likely this could happen with amdgpu as well. > > > >> > > > >> modprobe.blacklist=amdgpu > > > >> > > > >> works as well as the modeset parameter for this. > > > > > > > > People who build their own kernels run into trouble too. > > > > > > There have always been various more or less serious issues with building > > > amdgpu (and radeon) into the kernel. People who do so get to keep all > > > pieces when it breaks. > > fwiw, same roughly applies for i915. We try to make it work, by allowing > firmware to be loaded later on and asynchronously. But if you fail to > provide firmware the driver simply hangs forever. At least in certain > cases, for others we simply never clock gate/shutdown the chip. Also not > awesome (and we're closing all corresponding bug reports too). > > We don't yet need firmware for basic display support, so you'll get at > least a picture to be able to look at dmesg. If you remember to start X > without accel, that is :-) > > > > > Also does this work uniformly across all systems where it is a module? > > > > > > AFAIK yes. > > > > Sadly modprobe.blacklist doesn't prevent X/whatever from loading the > > module anyway. > > A generic "please don't bind anything to this device path" kernel property > would be really nice for this. And hopefully something that could be > merged into the drivers/base core code. > > Plus a generic and all-encompassing no_modeset^Wno_gfx_I_mean_it knob > would cover everything I think. > -Daniel > > > I use modprobe.blacklist myself all the time for i915 development, > > but I also have all GUI junk disabled as well so that I can load the > > module myself when I'm actually ready for it (typically after I've > > enabled netconsole). > > Oh, that's why modprobe.blacklist never works for me. TIL. The other common reason is snd_hda_intel. That one needs to be blacklisted at the same time, on modern Intel hw at least. Also one must remember to write it as "snd_hda_intel" instead of "snd-hda-intel", otherwise it doesn't do anything. -- Ville Syrjälä Intel OTC
