On Mon, Nov 03, 2025 at 02:18:10PM -0300, Gustavo Sousa wrote: > The Windows driver is rejecting non-monotonic ranges latency values for > Xe3. Let's make sure that we do not call make_wm_latency_monotonic() > for Xe3 and beyond.
So is Windows just refusing to drive the display at all if the latencies look invalid? If we're trying to match their behavior and avoid supporting bogus BIOS values, should we be propagating an error up the call stack and failing the display initialization? If that's too drastic and we want to try to forge onward anyway after raising the error message, then is there a reason to also avoid doing the value adjustment? I think the goal was to make sure we weren't letting bad settings go through silently, but once we've taken care of that it still seems like doing the adjustment might give us a higher chance of having a working display output? Matt > > Also, because of that, let's add a check at the end of > adjust_wm_latency() to ensure we raise a warning if the final list of > latency values is not monotonic. > > Cc: Ville Syrjälä <[email protected]> > Suggested-by: Ville Syrjälä <[email protected]> > Signed-off-by: Gustavo Sousa <[email protected]> > --- > drivers/gpu/drm/i915/display/skl_watermark.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c > b/drivers/gpu/drm/i915/display/skl_watermark.c > index d20c88ebe919..e13324af7afb 100644 > --- a/drivers/gpu/drm/i915/display/skl_watermark.c > +++ b/drivers/gpu/drm/i915/display/skl_watermark.c > @@ -3211,6 +3211,18 @@ static void make_wm_latency_monotonic(struct > intel_display *display) > } > } > > +static bool is_wm_latency_monotonic(struct intel_display *display) > +{ > + u16 *wm = display->wm.skl_latency; > + int level, num_levels = display->wm.num_levels; > + > + for (level = 1; level < num_levels; level++) > + if (wm[level] < wm[level - 1]) > + return false; > + > + return true; > +} > + > static void > adjust_wm_latency(struct intel_display *display) > { > @@ -3221,7 +3233,8 @@ adjust_wm_latency(struct intel_display *display) > > sanitize_wm_latency(display); > > - make_wm_latency_monotonic(display); > + if (DISPLAY_VER(display) < 30) > + make_wm_latency_monotonic(display); > > /* > * WaWmMemoryReadLatency > @@ -3241,6 +3254,8 @@ adjust_wm_latency(struct intel_display *display) > */ > if (need_16gb_dimm_wa(display)) > increase_wm_latency(display, 1); > + > + drm_WARN_ON(display->drm, !is_wm_latency_monotonic(display)); > } > > static void mtl_read_wm_latency(struct intel_display *display) > > -- > 2.51.0 > -- Matt Roper Graphics Software Engineer Linux GPU Platform Enablement Intel Corporation
