On Thu, Aug 15, 2013 at 05:30:27PM -0700, james.ausmus@xxxxxxxxx wrote: > From: Chris Wolfe <cwolfe@xxxxxxxxxxxx> > > Unfortunately some combinations of hardware seem to generate successful > communications on the aux channel, which always report deferred. As a > result native_write can wind up in an infinite loop. > > This hack adds a large (~10ms) retry limit to avoid a kernel panic, > while hopefully minimizing the impact on working hardware. > > Signed-off-by: cwolfe@xxxxxxxxxxxx > > BUG=chromium-os:34840 > TEST=Manually connect DP to VGA adapter to problem system. Added display > powers up and works normally, rather than black screen and reboot. > > Change-Id: Ib1b0001ca8004e65c9c5e353dbdb5e252fd88438 > Reviewed-on: https://gerrit.chromium.org/gerrit/34203 > Commit-Ready: Chris Wolfe <cwolfe@xxxxxxxxxxxx> > Reviewed-by: Chris Wolfe <cwolfe@xxxxxxxxxxxx> > Tested-by: Chris Wolfe <cwolfe@xxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/intel_dp.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > index e5d16bc..ac7d610 100644 > --- a/drivers/gpu/drm/i915/intel_dp.c > +++ b/drivers/gpu/drm/i915/intel_dp.c > @@ -491,6 +491,7 @@ intel_dp_aux_native_write(struct intel_dp *intel_dp, > uint8_t msg[20]; > int msg_bytes; > uint8_t ack; > + int try; > > intel_dp_check_edp(intel_dp); > if (send_bytes > 16) > @@ -501,7 +502,7 @@ intel_dp_aux_native_write(struct intel_dp *intel_dp, > msg[3] = send_bytes - 1; > memcpy(&msg[4], send, send_bytes); > msg_bytes = send_bytes + 4; > - for (;;) { > + for (try = 0; try < 100; try++) { > ret = intel_dp_aux_ch(intel_dp, msg, msg_bytes, &ack, 1); > if (ret < 0) > return ret; > @@ -512,6 +513,10 @@ intel_dp_aux_native_write(struct intel_dp *intel_dp, > else > return -EIO; > } > + if (try == 100) { > + DRM_ERROR("too many retries, giving up\n"); > + return -EREMOTEIO; > + } If we break out here, we need to reset the hw somewhere as it will still have the last command in the out queue. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
