drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE requests

When an i2c WRITE gets an i2c defer or short i2c ack reply, we are
supposed to switch the request from I2C_WRITE to I2C_WRITE_STATUS_UPDATE
when we continue to poll for the completion of the request.

v2: Don't assume DP_AUX_I2C_WRITE is 0 even though it is, to make the
    code more obvious to the casual reader (Jani)

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Resolve conflict due to changed context.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 80a02a4..5a55d90 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -422,6 +422,19 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)
               I2C_FUNC_10BIT_ADDR;
 }
 
+static void drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg)
+{
+       /*
+        * In case of i2c defer or short i2c ack reply to a write,
+        * we need to switch to WRITE_STATUS_UPDATE to drain the
+        * rest of the message
+        */
+       if ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE) {
+               msg->request &= DP_AUX_I2C_MOT;
+               msg->request |= DP_AUX_I2C_WRITE_STATUS_UPDATE;
+       }
+}
+
 /*
  * Transfer a single I2C-over-AUX message and handle various error conditions,
  * retrying the transaction as appropriate.  It is assumed that the
@@ -490,6 +503,8 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
                         * 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;
 
                case DP_AUX_I2C_REPLY_NACK:
@@ -507,6 +522,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
                        if (defer_i2c < 7)
                                defer_i2c++;
                        usleep_range(400, 500);
+                       drm_dp_i2c_msg_write_status_update(msg);
                        continue;
 
                default:
@@ -519,6 +535,14 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
        return -EREMOTEIO;
 }
 
+static void drm_dp_i2c_msg_set_request(struct drm_dp_aux_msg *msg,
+                                      const struct i2c_msg *i2c_msg)
+{
+       msg->request = (i2c_msg->flags & I2C_M_RD) ?
+               DP_AUX_I2C_READ : DP_AUX_I2C_WRITE;
+       msg->request |= DP_AUX_I2C_MOT;
+}
+
 /*
  * Keep retrying drm_dp_i2c_do_msg until all data has been transferred.
  *
@@ -572,10 +596,7 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
 
        for (i = 0; i < num; i++) {
                msg.address = msgs[i].addr;
-               msg.request = (msgs[i].flags & I2C_M_RD) ?
-                       DP_AUX_I2C_READ :
-                       DP_AUX_I2C_WRITE;
-               msg.request |= DP_AUX_I2C_MOT;
+               drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
                /* Send a bare address packet to start the transaction.
                 * Zero sized messages specify an address only (bare
                 * address) transaction.
@@ -583,6 +604,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
                msg.buffer = NULL;
                msg.size = 0;
                err = drm_dp_i2c_do_msg(aux, &msg);
+
+               /*
+                * Reset msg.request in case in case it got
+                * changed into a WRITE_STATUS_UPDATE.
+                */
+               drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
+
                if (err < 0)
                        break;
                /* We want each transaction to be as large as possible, but
@@ -595,6 +623,13 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
                        msg.size = min(transfer_size, msgs[i].len - j);
 
                        err = drm_dp_i2c_drain_msg(aux, &msg);
+
+                       /*
+                        * Reset msg.request in case in case it got
+                        * changed into a WRITE_STATUS_UPDATE.
+                        */
+                       drm_dp_i2c_msg_set_request(&msg, &msgs[i]);
+
                        if (err < 0)
                                break;
                        transfer_size = err;