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drm/dp: retry AUX transactions 32 times (v1.1)

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At least on two MST devices I've tested with, when
they are link training downstream, they are totally
unable to handle aux ch msgs, so they defer like nuts.
I tried 16, it wasn't enough, 32 seems better.

This fixes one Dell 4k monitor and one of the
MST hubs.

v1.1: fixup comment (Tom).

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Dave Airlie 2014-11-26 13:13:09 +10:00
parent b75478d1c7
commit 19a93f042f
1 changed files with 4 additions and 3 deletions
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7
drivers/gpu/drm/drm_dp_helper.c
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@ -186,10 +186,11 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
/*
* The specification doesn't give any recommendation on how often to
* retry native transactions, so retry 7 times like for I2C-over-AUX
* transactions.
* retry native transactions. We used to retry 7 times like for
* aux i2c transactions but real world devices this wasn't
* sufficient, bump to 32 which makes Dell 4k monitors happier.
*/
for (retry = 0; retry < 7; retry++) {
for (retry = 0; retry < 32; retry++) {
mutex_lock(&aux->hw_mutex);
err = aux->transfer(aux, &msg);