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drm/i915: Make wm latencies monotonic

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Some systems (eg. LNL Lenovo Thinkapd X1 Carbon) declare
semi-bogus non-monotonic WM latency values:
 WM0 latency not provided
 WM1 latency 100 usec
 WM2 latency 100 usec
 WM3 latency 100 usec
 WM4 latency 93 usec
 WM5 latency 100 usec

Apparently Windows just papers over the issue by bumping the
latencies for the higher watermark levels to make them monotonic
again. Do the same.

Cc: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250919193000.17665-12-ville.syrjala@linux.intel.com
Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
This commit is contained in:
Ville Syrjälä
2025-09-19 22:29:58 +03:00
parent 15bdae1072
commit d49564a5f7
1 changed files with 15 additions and 0 deletions
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15
drivers/gpu/drm/i915/display/skl_watermark.c
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@@ -3236,6 +3236,19 @@ static void sanitize_wm_latency(struct intel_display *display)
wm[level] = 0;
}
static void make_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] == 0)
break;
wm[level] = max(wm[level], wm[level-1]);
}
}
static void
adjust_wm_latency(struct intel_display *display)
{
@@ -3246,6 +3259,8 @@ adjust_wm_latency(struct intel_display *display)
sanitize_wm_latency(display);
make_wm_latency_monotonic(display);
/*
* WaWmMemoryReadLatency
*