From: Jesse Barnes Date: Mon, 1 Aug 2011 22:02:20 +0000 (-0700) Subject: drm/i915/dp: wait for previous AUX channel activity to clear X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=11bee43ebba0bfc92165c059f6e9869197ea8889;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git drm/i915/dp: wait for previous AUX channel activity to clear Before initiating a new read or write on the DP AUX channel, wait for any outstanding activity to complete. This may happen during normal retry behavior. If the wait fails (i.e. after 1ms the AUX channel is still busy) dump a backtrace to make the caller easier to spot. v2: use msleep instead, and timeout after 3ms (only ever saw 1 retry with msleep in testing) v3: fix backtrace check to trigger if the 3ms wait times out Fixes https://bugs.freedesktop.org/show_bug.cgi?id=38136. Signed-off-by: Jesse Barnes Reviewed-by: Keith Packard Signed-off-by: Keith Packard --- diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 449364187bc0..ba72fbcbbbc9 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -315,9 +315,17 @@ intel_dp_aux_ch(struct intel_dp *intel_dp, else precharge = 5; - if (I915_READ(ch_ctl) & DP_AUX_CH_CTL_SEND_BUSY) { - DRM_ERROR("dp_aux_ch not started status 0x%08x\n", - I915_READ(ch_ctl)); + /* Try to wait for any previous AUX channel activity */ + for (try = 0; try < 3; try++) { + status = I915_READ(ch_ctl); + if ((status & DP_AUX_CH_CTL_SEND_BUSY) == 0) + break; + msleep(1); + } + + if (try == 3) { + WARN(1, "dp_aux_ch not started status 0x%08x\n", + I915_READ(ch_ctl)); return -EBUSY; }