---

yaml
---
r: 307123
b: refs/heads/master
c: e646d57
h: refs/heads/master
i:
  307121: a7672c4
  307119: f8b47ad
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7a39a9d4767e8d22d60f2c4bf5eece4f4398c274
+refs/heads/master: e646d5773572bf52017983d758bdf05777dc5600

trunk/drivers/gpu/drm/i915/intel_i2c.c

@@ -324,26 +324,47 @@ gmbus_xfer(struct i2c_adapter *adapter,
 			goto clear_err;
 	}
 
-	goto done;
+	/* Mark the GMBUS interface as disabled after waiting for idle.
+	 * We will re-enable it at the start of the next xfer,
+	 * till then let it sleep.
+	 */
+	if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, 10))
+		DRM_INFO("GMBUS [%s] timed out waiting for idle\n",
+			 adapter->name);
+	I915_WRITE(GMBUS0 + reg_offset, 0);
+	ret = i;
+	goto out;
 
 clear_err:
+	/*
+	 * Wait for bus to IDLE before clearing NAK.
+	 * If we clear the NAK while bus is still active, then it will stay
+	 * active and the next transaction may fail.
+	 */
+	if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
+		     10))
+		DRM_INFO("GMBUS [%s] timed out after NAK\n", adapter->name);
+
 	/* Toggle the Software Clear Interrupt bit. This has the effect
 	 * of resetting the GMBUS controller and so clearing the
 	 * BUS_ERROR raised by the slave's NAK.
 	 */
 	I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT);
 	I915_WRITE(GMBUS1 + reg_offset, 0);
+	I915_WRITE(GMBUS0 + reg_offset, 0);
 
-done:
-	/* Mark the GMBUS interface as disabled after waiting for idle.
-	 * We will re-enable it at the start of the next xfer,
-	 * till then let it sleep.
+	DRM_DEBUG_DRIVER("GMBUS [%s] NAK for addr: %04x %c(%d)\n",
+			 adapter->name, msgs[i].addr,
+			 (msgs[i].flags & I2C_M_RD) ? 'r' : 'w', msgs[i].len);
+
+	/*
+	 * If no ACK is received during the address phase of a transaction,
+	 * the adapter must report -ENXIO.
+	 * It is not clear what to return if no ACK is received at other times.
+	 * So, we always return -ENXIO in all NAK cases, to ensure we send
+	 * it at least during the one case that is specified.
 	 */
-	if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, 10))
-		DRM_INFO("GMBUS [%s] timed out waiting for idle\n",
-			 bus->adapter.name);
-	I915_WRITE(GMBUS0 + reg_offset, 0);
-	ret = i;
+	ret = -ENXIO;
 	goto out;
 
 timeout: