drm/i915/hsw: Fix workaround for server AUX channel clock divisor

According to the HSW b-spec we need to try clock divisors of 63
and 72, each 3 or more times, when attempting DP AUX channel
communication on a server chipset.  This actually wasn't happening
due to a short-circuit that only checked the DP_AUX_CH_CTL_DONE bit
in status rather than checking that the operation was done and
that DP_AUX_CH_CTL_TIME_OUT_ERROR was not set.

[v2] Implemented alternate solution suggested by Jani Nikula.

Cc: stable@vger.kernel.org
Signed-off-by: Jim Bride <jim.bride@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index f27346e907b1..d714a4b5711e 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -880,10 +880,8 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
                                       DP_AUX_CH_CTL_RECEIVE_ERROR))
                                 continue;
                         if (status & DP_AUX_CH_CTL_DONE)
-                                break;
+                                goto done;
                 }
-                if (status & DP_AUX_CH_CTL_DONE)
-                        break;
         }
 
         if ((status & DP_AUX_CH_CTL_DONE) == 0) {
@@ -892,6 +890,7 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
                 goto out;
         }
 
+done:
         /* Check for timeout or receive error.
          * Timeouts occur when the sink is not connected
          */