From 1a738347df2ee4977459a8776fe2c62196bdcb1b Mon Sep 17 00:00:00 2001 From: Arindam Nath Date: Wed, 4 May 2016 23:39:59 +0530 Subject: [PATCH] drm/radeon: fix DP link training issue with second 4K monitor There is an issue observed when we hotplug a second DP 4K monitor to the system. Sometimes, the link training fails for the second monitor after HPD interrupt generation. The issue happens when some queued or deferred transactions are already present on the AUX channel when we initiate a new transcation to (say) get DPCD or during link training. We set AUX_IGNORE_HPD_DISCON bit in the AUX_CONTROL register so that we can ignore any such deferred transactions when a new AUX transaction is initiated. Signed-off-by: Arindam Nath Reviewed-by: Alex Deucher Signed-off-by: Alex Deucher Cc: stable@vger.kernel.org --- drivers/gpu/drm/radeon/radeon_dp_auxch.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/radeon/radeon_dp_auxch.c b/drivers/gpu/drm/radeon/radeon_dp_auxch.c index 3b0c229d7dcd..db64e0062689 100644 --- a/drivers/gpu/drm/radeon/radeon_dp_auxch.c +++ b/drivers/gpu/drm/radeon/radeon_dp_auxch.c @@ -105,7 +105,7 @@ radeon_dp_aux_transfer_native(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg tmp &= AUX_HPD_SEL(0x7); tmp |= AUX_HPD_SEL(chan->rec.hpd); - tmp |= AUX_EN | AUX_LS_READ_EN; + tmp |= AUX_EN | AUX_LS_READ_EN | AUX_HPD_DISCON(0x1); WREG32(AUX_CONTROL + aux_offset[instance], tmp);