[PATCH 02/14] drm/amd/display: Correct the reply value when AUX write incomplete

[Ray Wu]

From: Wayne Lin <wayne....@amd.com>

[Why]
Now forcing aux->transfer to return 0 when incomplete AUX write is
inappropriate. It should return bytes have been transferred.

[How]
aux->transfer is asked not to change original msg except reply field of
drm_dp_aux_msg structure. Copy the msg->buffer when it's write request,
and overwrite the first byte when sink reply 1 byte indicating partially
written byte number. Then we can return the correct value without
changing the original msg.

Fixes: 6285f12bc54c ("drm/amd/display: Fix wrong handling for AUX_DEFER case")
Cc: sta...@vger.kernel.org
Cc: Mario Limonciello <mario.limoncie...@amd.com>
Cc: Alex Deucher <alexander.deuc...@amd.com>
Reviewed-by: Ray Wu <ray...@amd.com>
Signed-off-by: Wayne Lin <wayne....@amd.com>
Signed-off-by: Ray Wu <ray...@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c      |  3 ++-
 .../drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c    | 10 ++++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 8984e211dd1c..36c16030fca9 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -12853,7 +12853,8 @@ int amdgpu_dm_process_dmub_aux_transfer_sync(
                /* The reply is stored in the top nibble of the command. */
                payload->reply[0] = (adev->dm.dmub_notify->aux_reply.command >> 
4) & 0xF;
 
-       if (!payload->write && p_notify->aux_reply.length)
+       /*write req may receive a byte indicating partially written number as 
well*/
+       if (p_notify->aux_reply.length)
                memcpy(payload->data, p_notify->aux_reply.data,
                                p_notify->aux_reply.length);
 
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 d19aea595722..0d7b72c75802 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
@@ -62,6 +62,7 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
        enum aux_return_code_type operation_result;
        struct amdgpu_device *adev;
        struct ddc_service *ddc;
+       uint8_t copy[16];
 
        if (WARN_ON(msg->size > 16))
                return -E2BIG;
@@ -77,6 +78,11 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
                        (msg->request & DP_AUX_I2C_WRITE_STATUS_UPDATE) != 0;
        payload.defer_delay = 0;
 
+       if (payload.write) {
+               memcpy(copy, msg->buffer, msg->size);
+               payload.data = copy;
+       }
+
        result = dc_link_aux_transfer_raw(TO_DM_AUX(aux)->ddc_service, &payload,
                                      &operation_result);
 
@@ -100,9 +106,9 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
         */
        if (payload.write && result >= 0) {
                if (result) {
-                       /*one byte indicating partially written bytes. Force 0 
to retry*/
+                       /*one byte indicating partially written bytes*/
                        drm_info(adev_to_drm(adev), "amdgpu: AUX partially 
written\n");
-                       result = 0;
+                       result = payload.data[0];
                } else if (!payload.reply[0])
                        /*I2C_ACK|AUX_ACK*/
                        result = msg->size;
-- 
2.43.0