Merge tag 'qcom-soc-for-3.16-2' of git://git.kernel.org/pub/scm/linux/kernel/git...

[pandora-kernel.git] / drivers / gpu / drm / drm_dp_helper.c

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 2767148..4b6e6f3 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -577,7 +577,9 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)
 
 /*
  * Transfer a single I2C-over-AUX message and handle various error conditions,
- * retrying the transaction as appropriate.
+ * retrying the transaction as appropriate.  It is assumed that the
+ * aux->transfer function does not modify anything in the msg other than the
+ * reply field.
  */
 static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 {
@@ -665,11 +667,26 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
 {
        struct drm_dp_aux *aux = adapter->algo_data;
        unsigned int i, j;
+       struct drm_dp_aux_msg msg;
+       int err = 0;
 
-       for (i = 0; i < num; i++) {
-               struct drm_dp_aux_msg msg;
-               int err;
+       memset(&msg, 0, sizeof(msg));
 
+       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;
+               /* Send a bare address packet to start the transaction.
+                * Zero sized messages specify an address only (bare
+                * address) transaction.
+                */
+               msg.buffer = NULL;
+               msg.size = 0;
+               err = drm_dp_i2c_do_msg(aux, &msg);
+               if (err < 0)
+                       break;
                /*
                 * Many hardware implementations support FIFOs larger than a
                 * single byte, but it has been empirically determined that
@@ -678,30 +695,28 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
                 * transferred byte-by-byte.
                 */
                for (j = 0; j < msgs[i].len; j++) {
-                       memset(&msg, 0, sizeof(msg));
-                       msg.address = msgs[i].addr;
-
-                       msg.request = (msgs[i].flags & I2C_M_RD) ?
-                                       DP_AUX_I2C_READ :
-                                       DP_AUX_I2C_WRITE;
-
-                       /*
-                        * All messages except the last one are middle-of-
-                        * transfer messages.
-                        */
-                       if ((i < num - 1) || (j < msgs[i].len - 1))
-                               msg.request |= DP_AUX_I2C_MOT;
-
                        msg.buffer = msgs[i].buf + j;
                        msg.size = 1;
 
                        err = drm_dp_i2c_do_msg(aux, &msg);
                        if (err < 0)
-                               return err;
+                               break;
                }
+               if (err < 0)
+                       break;
        }
+       if (err >= 0)
+               err = num;
+       /* Send a bare address packet to close out the transaction.
+        * Zero sized messages specify an address only (bare
+        * address) transaction.
+        */
+       msg.request &= ~DP_AUX_I2C_MOT;
+       msg.buffer = NULL;
+       msg.size = 0;
+       (void)drm_dp_i2c_do_msg(aux, &msg);
 
-       return num;
+       return err;
 }
 
 static const struct i2c_algorithm drm_dp_i2c_algo = {