| From e058c945e03a629c99606452a6931f632dd28903 Mon Sep 17 00:00:00 2001 |
| From: Jim Bride <jim.bride@linux.intel.com> |
| Date: Wed, 27 May 2015 10:21:48 -0700 |
| Subject: drm/i915/hsw: Fix workaround for server AUX channel clock divisor |
| |
| From: Jim Bride <jim.bride@linux.intel.com> |
| |
| commit e058c945e03a629c99606452a6931f632dd28903 upstream. |
| |
| 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. |
| |
| Signed-off-by: Jim Bride <jim.bride@linux.intel.com> |
| Signed-off-by: Jani Nikula <jani.nikula@intel.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/gpu/drm/i915/intel_dp.c | 5 ++--- |
| 1 file changed, 2 insertions(+), 3 deletions(-) |
| |
| --- a/drivers/gpu/drm/i915/intel_dp.c |
| +++ b/drivers/gpu/drm/i915/intel_dp.c |
| @@ -881,10 +881,8 @@ intel_dp_aux_ch(struct intel_dp *intel_d |
| 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) { |
| @@ -893,6 +891,7 @@ intel_dp_aux_ch(struct intel_dp *intel_d |
| goto out; |
| } |
| |
| +done: |
| /* Check for timeout or receive error. |
| * Timeouts occur when the sink is not connected |
| */ |
