From: Wayne Lin Wayne.Lin@amd.com

[Why] We incorrectly ack all bytes get written when the reply actually is defer. When it's defer, means sink is not ready for the request. We should retry the request.

[How] Only reply all data get written when receive I2C_ACK|AUX_ACK. Otherwise, reply the number of actual written bytes received from the sink. Add some messages to facilitate debugging as well.

Fixes: ad6756b4d773 ("drm/amd/display: Shift dc link aux to aux_payload") Cc: stable@vger.kernel.org Reviewed-by: Ray Wu ray.wu@amd.com Signed-off-by: Wayne Lin Wayne.Lin@amd.com Signed-off-by: Ray Wu ray.wu@amd.com --- .../display/amdgpu_dm/amdgpu_dm_mst_types.c | 28 ++++++++++++++++--- 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c index d8dcfb3efaaa..d19aea595722 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c @@ -51,6 +51,9 @@

#define PEAK_FACTOR_X1000 1006

+/* + * This function handles both native AUX and I2C-Over-AUX transactions. + */ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { @@ -87,15 +90,25 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux, if (adev->dm.aux_hpd_discon_quirk) { if (msg->address == DP_SIDEBAND_MSG_DOWN_REQ_BASE && operation_result == AUX_RET_ERROR_HPD_DISCON) { - result = 0; + result = msg->size; operation_result = AUX_RET_SUCCESS; } }

- if (payload.write && result >= 0) - result = msg->size; + /* + * result equals to 0 includes the cases of AUX_DEFER/I2C_DEFER + */ + if (payload.write && result >= 0) { + if (result) { + /*one byte indicating partially written bytes. Force 0 to retry*/ + drm_info(adev_to_drm(adev), "amdgpu: AUX partially written\n"); + result = 0; + } else if (!payload.reply[0]) + /*I2C_ACK|AUX_ACK*/ + result = msg->size; + }

- if (result < 0) + if (result < 0) { switch (operation_result) { case AUX_RET_SUCCESS: break; @@ -114,6 +127,13 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux, break; }

+ drm_info(adev_to_drm(adev), "amdgpu: DP AUX transfer fail:%d\n", operation_result); + } + + if (payload.reply[0]) + drm_info(adev_to_drm(adev), "amdgpu: AUX reply command not ACK: 0x%02x.", + payload.reply[0]); + return result; }