From 26b3a8b25e68da478965f3054e4e213a48519fb6 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Sat, 8 Feb 2025 00:31:52 +0200 Subject: [PATCH] drm/i915/dsb: Move the +1 usec adjustment into dsb_wait_usec() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The "wait usec" DSB command doesn't quite seem to able to guarantee that it always waits at least the specified amount of usecs. Some of that could be just because it supposedly just does some kind of dumb timestamp comparison internally. But I also see cases where two hardware timestamps sampled on each side of the "wait usec" command come out one less than expected. So it looks like we always need at least a +1 to guarantee that we never wait less than specified. Always apply that adjustment in dsb_wait_usec(). Signed-off-by: Ville Syrjälä Link: https://patchwork.freedesktop.org/patch/msgid/20250207223159.14132-2-ville.syrjala@linux.intel.com Reviewed-by: Ankit Nautiyal --- drivers/gpu/drm/i915/display/intel_dsb.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c index 2f2812c23972..f8bd6fad0c87 100644 --- a/drivers/gpu/drm/i915/display/intel_dsb.c +++ b/drivers/gpu/drm/i915/display/intel_dsb.c @@ -369,7 +369,8 @@ void intel_dsb_interrupt(struct intel_dsb *dsb) void intel_dsb_wait_usec(struct intel_dsb *dsb, int count) { - intel_dsb_emit(dsb, count, + /* +1 to make sure we never wait less time than asked for */ + intel_dsb_emit(dsb, count + 1, DSB_OPCODE_WAIT_USEC << DSB_OPCODE_SHIFT); } @@ -622,7 +623,7 @@ void intel_dsb_wait_vblank_delay(struct intel_atomic_state *state, const struct intel_crtc_state *crtc_state = intel_pre_commit_crtc_state(state, crtc); int usecs = intel_scanlines_to_usecs(&crtc_state->hw.adjusted_mode, - dsb_vblank_delay(state, crtc)) + 1; + dsb_vblank_delay(state, crtc)); intel_dsb_wait_usec(dsb, usecs); } -- 2.50.1