On Wed, 27 May 2015, jim.bride@xxxxxxxxxxxxxxx wrote:
> From: Jim Bride <jim.bride@xxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 0edc305..7d1e024 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -893,10 +893,8 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
> 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) {
> @@ -905,6 +903,7 @@ 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
> */
> --
> 1.9.1
>
--
Jani Nikula, Intel Open Source Technology Center
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