Re: [PATCH] drm/i915/ilk: Wait one vblank before enabling audio

[Jani Nikula <jani.nikula@linux.intel.com>]

On Sat, 21 May 2016, Lyude <cpaul@redhat.com> wrote:
> We no longer call ilk_audio_codec_enable() while we have vblanks
> disabled. As such, we can finally fix this and stop the occasional pipe
> underruns I'm seeing on this Dell OptiPlex 990.
>
> Cc: stable@vger.kernel.org

Even if this were the right fix now, I'd be wary of adding a blanket cc:
stable to kernels where we still have vblanks disabled when this
function gets called.

Whoever pushes this, please ensure the cc: stable gets dropped from the
commit.

Thanks,
Jani.

> Signed-off-by: Lyude <cpaul@redhat.com>
> ---
>  drivers/gpu/drm/i915/intel_audio.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
> index 7d281b4..0d685fe 100644
> --- a/drivers/gpu/drm/i915/intel_audio.c
> +++ b/drivers/gpu/drm/i915/intel_audio.c
> @@ -423,12 +423,8 @@ static void ilk_audio_codec_enable(struct drm_connector *connector,
>  	if (WARN_ON(port == PORT_A))
>  		return;
>  
> -	/*
> -	 * FIXME: We're supposed to wait for vblank here, but we have vblanks
> -	 * disabled during the mode set. The proper fix would be to push the
> -	 * rest of the setup into a vblank work item, queued here, but the
> -	 * infrastructure is not there yet.
> -	 */
> +	/* Need to wait one vblank before enabling audio */
> +	intel_wait_for_vblank(connector->dev, pipe);
>  
>  	if (HAS_PCH_IBX(connector->dev)) {
>  		hdmiw_hdmiedid = IBX_HDMIW_HDMIEDID(pipe);

-- 
Jani Nikula, Intel Open Source Technology Center
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