[Intel-gfx] [PATCH 2/2] drm/i915: Wait for pipe to start on i830 as well

[Chris Wilson]

Quoting Ville Syrjala (2017-11-13 15:32:15)
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> We should make sure the pipe has fully started when we enable it from
> the i830 "power well". Otherwise theoretically i830 could also hit
> problems with vblank timestamps jumping around (since we skip the
> wait during modeset on i830). Additionally moving planes between the
> pipes etc. might not work correctly until both pipes are actually up and
> running.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 810b1147a0ac..467f72df9db3 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -14704,6 +14704,9 @@ void i830_enable_pipe(struct drm_i915_private *dev_priv, enum pipe pipe)
>  
>         I915_WRITE(PIPECONF(pipe), PIPECONF_ENABLE | PIPECONF_PROGRESSIVE);
>         POSTING_READ(PIPECONF(pipe));
> +
> +       if (wait_for(pipe_dsl_stopped(dev_priv, pipe, false), 100))
> +               DRM_ERROR("pipe %c on wait timed out\n", pipe_name(pipe));

This seems to fit in the with the pattern of wait for vblank after
enabling, but more refined (i.e. don't wait for the whole frame, just
wait for the frame to start scanning out).

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

Why not intel_wait_for_pipe_on() here?
-Chris