[Intel-gfx] [PATCH] drm/i915/dp: Don't stop the link when retraining

[Jesse Barnes]

On Mon,  3 Nov 2014 11:39:24 +0100
Daniel Vetter <daniel.vetter at ffwll.ch> wrote:

> On pre-ddi platforms we don't shut down the link when changing link
> training parameters. Except when clock recovery fails too hard and we
> restart with channel eq training. Which doesn't make a lot of sense
> really, since just stopping/restarting the DP port at this point
> violates the modeset sequence documented in the Bspec.
> 
> So let's tempt fate and try this.
> 
> This patch is motivated by a WARN_ON triggered by
> 
> commit bc76e320f21f8bd790a72bd5dc06909617432352
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date:   Tue May 20 22:46:50 2014 +0200
> 
>     drm/i915: Drop now misleading DDI comment from dp_link_down
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=85670
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c index f6a3fdd5589e..e48ca3a87199
> 100644 --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3598,7 +3598,6 @@ intel_dp_complete_link_train(struct intel_dp
> *intel_dp) 
>  		/* Try 5 times, then try clock recovery if that
> fails */ if (tries > 5) {
> -			intel_dp_link_down(intel_dp);
>  			intel_dp_start_link_train(intel_dp);
>  			intel_dp_set_link_train(intel_dp, &DP,
>  						training_pattern |


Didn't look like it helped the reporter?  Or at least I didn't see it
tried in the bug above...

I'm a bit worried about this because istr the spec indicating that we
do need to down the link when retrying clock recovery.  I guess I'll
need to check again.