Re: [PATCH 2/5] drm/i915: keep AUX powered while PSR is enabled

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José Roberto de Souza <jose.souza@xxxxxxxxx> writes:

> Hardware can send AUX transactions by it self when PSR is enabled and it
> expects that AUX is kept powered up.
>
> From spec:
>
> "Each DisplayPort Aux channel has an Aux IO Power Request. If an Aux
> channel will not be used, it does not need to be powered up.
>
> PSR spontaneously sends Aux transactions.  If PSR is enabled on a port,
> then the associated Aux IO must be kept powered up."
>
> BSpec: 4230
> BSpec: 17722

It seems here this is only needed for AUX IO PWs.
So maybe for that we would need some thing like POWER_DOMAIN_PSR_AUX_* that is
part of {GLK,CNL}_DISPLAY_AUX_*_POWER_DOMAINS

So here we would get and put the specific PSR_AUX ones instead of the
whole dp aux. We don't need to keep the entire well up apparently.
At least I hope we don't.

>
> Signed-off-by: José Roberto de Souza <jose.souza@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/intel_psr.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
> index 8b456e4e1b47..225fde979e57 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -516,6 +516,12 @@ void intel_psr_enable(struct intel_dp *intel_dp,
>  		goto unlock;
>  	}
>  
> +	/*
> +	 * hardware can send AUX transactions by it self when PSR is enabled,
> +	 * and it expects that AUX is kept powered up.
> +	 */
> +	intel_display_power_get(dev_priv, intel_dp->aux_power_domain);
> +
>  	dev_priv->psr.psr2_support = crtc_state->has_psr2;
>  	dev_priv->psr.busy_frontbuffer_bits = 0;
>  
> @@ -656,6 +662,8 @@ void intel_psr_disable(struct intel_dp *intel_dp,
>  	/* Disable PSR on Sink */
>  	drm_dp_dpcd_writeb(&intel_dp->aux, DP_PSR_EN_CFG, 0);
>  
> +	intel_display_power_put(dev_priv, intel_dp->aux_power_domain);
> +
>  	dev_priv->psr.enabled = NULL;
>  	mutex_unlock(&dev_priv->psr.lock);
>  
> -- 
> 2.16.1
>
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