[Why] Notice AUX request format of I2C-over-AUX with Write_Status_Update_Request flag set is incorrect. It should be address only request without length and data like: "SYNC->COM3:0 (= 0110)|0000-> 0000|0000-> 0|7-bit I2C address (the same as the last)-> STOP->".

[How] Refer to DP v2.1 Table 2-178, correct the Write_Status_Update_Request to be address only request.

Note that we might receive 0 returned by aux->transfer() when receive reply I2C_ACK|AUX_ACK of Write_Status_Update_Request transaction. Which indicating all data bytes get written. We should avoid to return 0 bytes get transferred under this case.

Fixes: 68ec2a2a2481 ("drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE requests") Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Jani Nikula jani.nikula@intel.com Cc: Mario Limonciello mario.limonciello@amd.com Cc: Harry Wentland harry.wentland@amd.com Cc: stable@vger.kernel.org Signed-off-by: Wayne Lin Wayne.Lin@amd.com --- drivers/gpu/drm/display/drm_dp_helper.c | 45 +++++++++++++++++++++---- 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index 57828f2b7b5a..0c8cba7ed875 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -1857,6 +1857,12 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) I2C_FUNC_10BIT_ADDR; }

+static inline bool +drm_dp_i2c_msg_is_write_status_update(struct drm_dp_aux_msg *msg) +{ + return ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE_STATUS_UPDATE); +} + static void drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg) { /* @@ -1965,6 +1971,7 @@ MODULE_PARM_DESC(dp_aux_i2c_speed_khz, static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { unsigned int retry, defer_i2c; + struct drm_dp_aux_msg orig_msg = *msg; int ret; /* * DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device @@ -1976,6 +1983,12 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) int max_retries = max(7, drm_dp_i2c_retry_count(msg, dp_aux_i2c_speed_khz));

for (retry = 0, defer_i2c = 0; retry < (max_retries + defer_i2c); retry++) { + if (drm_dp_i2c_msg_is_write_status_update(msg)) { + /* Address only transaction */ + msg->buffer = NULL; + msg->size = 0; + } + ret = aux->transfer(aux, msg); if (ret < 0) { if (ret == -EBUSY) @@ -1993,7 +2006,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) else drm_dbg_kms(aux->drm_dev, "%s: transaction failed: %d\n", aux->name, ret); - return ret; + goto out; }

@@ -2008,7 +2021,8 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) case DP_AUX_NATIVE_REPLY_NACK: drm_dbg_kms(aux->drm_dev, "%s: native nack (result=%d, size=%zu)\n", aux->name, ret, msg->size); - return -EREMOTEIO; + ret = -EREMOTEIO; + goto out;

case DP_AUX_NATIVE_REPLY_DEFER: drm_dbg_kms(aux->drm_dev, "%s: native defer\n", aux->name); @@ -2027,24 +2041,35 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) default: drm_err(aux->drm_dev, "%s: invalid native reply %#04x\n", aux->name, msg->reply); - return -EREMOTEIO; + ret = -EREMOTEIO; + goto out; }

switch (msg->reply & DP_AUX_I2C_REPLY_MASK) { case DP_AUX_I2C_REPLY_ACK: + /* + * When I2C write firstly get defer and get ack after + * retries by wirte_status_update, we have to return + * all data bytes get transferred instead of 0. + */ + if (drm_dp_i2c_msg_is_write_status_update(msg) && ret == 0) + ret = orig_msg.size; + /* * Both native ACK and I2C ACK replies received. We * can assume the transfer was successful. */ if (ret != msg->size) drm_dp_i2c_msg_write_status_update(msg); - return ret; + + goto out;

case DP_AUX_I2C_REPLY_NACK: drm_dbg_kms(aux->drm_dev, "%s: I2C nack (result=%d, size=%zu)\n", aux->name, ret, msg->size); aux->i2c_nack_count++; - return -EREMOTEIO; + ret = -EREMOTEIO; + goto out;

case DP_AUX_I2C_REPLY_DEFER: drm_dbg_kms(aux->drm_dev, "%s: I2C defer\n", aux->name); @@ -2063,12 +2088,18 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) default: drm_err(aux->drm_dev, "%s: invalid I2C reply %#04x\n", aux->name, msg->reply); - return -EREMOTEIO; + ret = -EREMOTEIO; + goto out; } }

drm_dbg_kms(aux->drm_dev, "%s: Too many retries, giving up\n", aux->name); - return -EREMOTEIO; + ret = -EREMOTEIO; +out: + /* In case we change original msg by Write_Status_Update*/ + msg->buffer = orig_msg.buffer; + msg->size = orig_msg.size; + return ret; }

static void drm_dp_i2c_msg_set_request(struct drm_dp_aux_msg *msg,