From: Arindam Nath arindam.nath@amd.com

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 --- 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 3b0c229..db64e00 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);