1 files changed, 12 insertions, 9 deletions

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 4a9707dd0f9..1991a4408cf 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -396,11 +396,22 @@ 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 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. But we have to be careful to not return
+         * spurious -ENXIO because that will prevent i2c and drm edid functions
+         * from retrying. So return -ENXIO only when gmbus properly quiescents -
+         * timing out seems to happen when there _is_ a ddc chip present, but
+         * it's slow responding and only answers on the 2nd retry.
          */
+        ret = -ENXIO;
         if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
-                     10))
+                     10)) {
                 DRM_DEBUG_KMS("GMBUS [%s] timed out after NAK\n",
                               adapter->name);
+                ret = -ETIMEDOUT;
+        }
 
         /* Toggle the Software Clear Interrupt bit. This has the effect
          * of resetting the GMBUS controller and so clearing the
@@ -414,14 +425,6 @@ clear_err:
                          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.
-         */
-        ret = -ENXIO;
         goto out;
 
 timeout: