From: Ville Syrjälä Date: Fri, 7 Feb 2025 22:31:52 +0000 (+0200) Subject: drm/i915/dsb: Move the +1 usec adjustment into dsb_wait_usec() X-Git-Tag: v6.15-rc1~120^2~16^2~81 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=26b3a8b25e68da478965f3054e4e213a48519fb6;p=thirdparty%2Fkernel%2Flinux.git drm/i915/dsb: Move the +1 usec adjustment into dsb_wait_usec() 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 --- diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c index 2f2812c239725..f8bd6fad0c871 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); }