From bf9e3b6ffd76da38dd4961c65d80571b25bf10a5 Mon Sep 17 00:00:00 2001 From: Ville Syrjälä Date: Tue, 3 Mar 2026 11:54:14 +0200 Subject: drm/i915/vrr: Configure VRR timings after enabling TRANS_DDI_FUNC_CTL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 237aab549676288d9255bb8dcc284738e56eaa31 upstream. Apparently ICL may hang with an MCE if we write TRANS_VRR_VMAX/FLIPLINE before enabling TRANS_DDI_FUNC_CTL. Personally I was only able to reproduce a hang (on an Dell XPS 7390 2-in-1) with an external display connected via a dock using a dodgy type-C cable that made the link training fail. After the failed link training the machine would hang. TGL seemed immune to the problem for whatever reason. BSpec does tell us to configure VRR after enabling TRANS_DDI_FUNC_CTL as well. The DMC firmware also does the VRR restore in two stages: - first stage seems to be unconditional and includes TRANS_VRR_CTL and a few other VRR registers, among other things - second stage is conditional on the DDI being enabled, and includes TRANS_DDI_FUNC_CTL and TRANS_VRR_VMAX/VMIN/FLIPLINE, among other things So let's reorder the steps to match to avoid the hang, and toss in an extra WARN to make sure we don't screw this up later. BSpec: 22243 Cc: stable@vger.kernel.org Cc: Ankit Nautiyal Reported-by: Benjamin Tissoires Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15777 Tested-by: Benjamin Tissoires Fixes: dda7dcd9da73 ("drm/i915/vrr: Use fixed timings for platforms that support VRR") Signed-off-by: Ville Syrjälä Link: https://patch.msgid.link/20260303095414.4331-1-ville.syrjala@linux.intel.com Reviewed-by: Ankit Nautiyal (cherry picked from commit 93f3a267c3dd4d811b224bb9e179a10d81456a74) Signed-off-by: Tvrtko Ursulin Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/display/intel_display.c | 1 - 1 file changed, 1 deletion(-) (limited to 'drivers/gpu/drm/i915/display/intel_display.c') diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c index 095a319f8bc9..144f232d61c5 100644 --- a/drivers/gpu/drm/i915/display/intel_display.c +++ b/drivers/gpu/drm/i915/display/intel_display.c @@ -1614,7 +1614,6 @@ static void hsw_configure_cpu_transcoder(const struct intel_crtc_state *crtc_sta } intel_set_transcoder_timings(crtc_state); - intel_vrr_set_transcoder_timings(crtc_state); if (cpu_transcoder != TRANSCODER_EDP) intel_de_write(display, TRANS_MULT(display, cpu_transcoder), -- cgit v1.2.3