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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 <arindam.nath@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Arindam Nath 2016-05-04 23:39:59 +05:30 committed by Alex Deucher
parent fca097169f
commit 1a738347df
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/radeon/radeon_dp_auxch.c
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@ -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);