On Thu, 16 Sep 2021, Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote: > Hi, > > On 16/09/2021 05:37, Hugh Dickins wrote: >> Two Lenovo ThinkPads, old T420s (2011), newer X1 Carbon 5th gen (2017): >> i915 working fine on both up to 5.14, but blank screens booting 5.15-rc1, >> kernel crashed in some way. > > T420s could be SandyBridge and X1 Carbon KabyLake. > >> I wanted to say what i915 generations these are, but don't know where >> to look - I don't see it in dmesg, even when DRM_I915_DEBUG enabled. >> >> Possibly relevant: builtin kernels, CONFIG_MODULES off, no initrd. >> >> On the older laptop: >> >> First bisection showed first bad commit >> 41e5c17ebfc2 "drm/i915/guc/slpc: Sysfs hooks for SLPC" >> >> But reverting that still crashed boot with blank screen (and >> reverting the two related commits after it made no difference). >> >> Second bisection, starting from 5.15-rc1 bad and 41e5c17ebfc2 "good", >> but patching it out each time before building, showed first bad commit >> 3ffe82d701a4 "drm/i915/xehp: handle new steering options" >> >> That one did not revert cleanly from 5.15-rc1, but reverting >> 927dfdd09d8c "drm/i915/dg2: Add SQIDI steering" then >> 1705f22c86fb "drm/i915/dg2: Update steering tables" then >> 768fe28dd3dc "drm/i915/xehpsdv: Define steering tables" then >> 3ffe82d701a4 "drm/i915/xehp: handle new steering options" >> worked (there was one very easy fixup needed somewhere). >> >> And 5.15-rc1 with those five reversions boots and runs fine... >> on that older laptop. But reverting those from the kernel on the >> newer laptop did not help at all, still booting with blank screen >> (or no more lines shown after the switch from VGA). Put them back. > > Bisect results sound suspicious since the steering patches do not come > into play on SandyBridge. > >> On the newer laptop, bisection showed first bad commit >> 62eaf0ae217d "drm/i915/guc: Support request cancellation" >> >> And 5.15-rc1 with that reverted boots and runs fine on the newer. > But not on the older laptop? > > Given bisect points to this, it may be worth trying to build both > kernels with CONFIG_DRM_I915_REQUEST_TIMEOUT=0 (no reverts) to see what > happens. But first the logs which I'll ask next. > >> I am hoping that there will be some i915 fixups to come in a later rc! >> May be nothing more than uninitialized variables or NULL pointers. >> You'll probably want more info from me: please ask, but I'm slow. > > Kernel logs with drm.debug=0xe, with the broken black screen state, > would probably answer a lot of questions if you could gather it from > both machines? And for that, I think it's best to file separate bugs at [1] and attach the logs there. It helps keep the info in one place. Thanks. BR, Jani. [1] https://gitlab.freedesktop.org/drm/intel/issues/new > > Regards, > > Tvrtko -- Jani Nikula, Intel Open Source Graphics Center
