From d4cb3fd9b548b8bfe2a712ec920b9ebabd3547ab Mon Sep 17 00:00:00 2001 From: Matthew Auld Date: Wed, 19 Oct 2016 22:29:53 +0100 Subject: [PATCH] drm/i915/dp: add lane_count check in intel_dp_check_link_status MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently it's entirely possible to go through the link training step without first determining the lane_count, which is silly since we end up doing a bunch of aux transfers of size = 0, as highlighted by WARN_ON(!msg->buffer != !msg->size), and can only ever result in a 'failed to update link training' message. This can be observed during intel_dp_long_pulse where we can do the link training step, but before we have had a chance to set the link params. To avoid this we add an extra check for the lane_count in intel_dp_check_link_status, which should prevent us from doing the link training step prematurely. v2: add WARN_ON_ONCE and FIXME comment (Ville) References: https://bugs.freedesktop.org/show_bug.cgi?id=97344 Cc: Ville Syrjälä Cc: Mika Kahola Signed-off-by: Matthew Auld Link: http://patchwork.freedesktop.org/patch/msgid/1476912593-10019-1-git-send-email-matthew.auld@intel.com Signed-off-by: Ville Syrjälä --- drivers/gpu/drm/i915/intel_dp.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index e03e79f7714a..f30db8f2425e 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -4041,6 +4041,11 @@ intel_dp_check_link_status(struct intel_dp *intel_dp) if (!to_intel_crtc(intel_encoder->base.crtc)->active) return; + /* FIXME: we need to synchronize this sort of stuff with hardware + * readout */ + if (WARN_ON_ONCE(!intel_dp->lane_count)) + return; + /* if link training is requested we should perform it always */ if ((intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) || (!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {