Re: [PATCH v3 08/11] drm/i915: Remove the unneeded AUX power ref from intel_dp_hpd_pulse()

["Souza, Jose" <jose.souza@intel.com>]

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On Thu, 2019-05-09 at 20:34 +0300, Imre Deak wrote:
> The power get/put was added in
> 
> commit 1c767b339b39 ("drm/i915: take display port power domain in DP
> HPD handler")
> Author: Imre Deak <imre.deak@intel.com>
> Date:   Mon Aug 18 14:42:42 2014 +0300
> 
> to account for the HW access in ibx_digital_port_connected(). This
> latter call was in turn removed in
> 
> commit 7d23e3c37bb3 ("drm/i915: Cleaning up intel_dp_hpd_pulse")
> Author: Shubhangi Shrivastava <shubhangi.shrivastava@intel.com>
> Date:   Wed Mar 30 18:05:23 2016 +0530
> 
> after which we didn't actually need the power reference.
> 
> One way we are accessing the HW during HPD pulse handling is via DP
> AUX
> transfers, but the transfer function takes its own reference, so
> doesn't
> need the reference in intel_dp_hpd_pulse().

<Did not look at the other patches />

The problem of removing that reference is that every aux transfer will
take a little bit more of time because it will need to wait the aux
power well to be enabled/disabled, taking one reference before hand
save us that.

> 
> The other spot is in
> 
> 	intel_psr_short_pulse()->intel_psr_disable_locked()
> 
> but that can only happen when the panel is enabled with the
> corresponding modeset already holding the required power reference.
> 
> v2:
> - Remove the unneeded power get/put from intel_psr_disable_locked().
>   (Ville)
> - Checkpatch commit quoting format fix in the commit log.
> 
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: José Roberto de Souza <jose.souza@intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 20 ++++----------------
>  1 file changed, 4 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index 553071812f69..8a91b453b2e9 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -6302,9 +6302,6 @@ enum irqreturn
>  intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool
> long_hpd)
>  {
>  	struct intel_dp *intel_dp = &intel_dig_port->dp;
> -	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> -	enum irqreturn ret = IRQ_NONE;
> -	intel_wakeref_t wakeref;
>  
>  	if (long_hpd && intel_dig_port->base.type == INTEL_OUTPUT_EDP)
> {
>  		/*
> @@ -6327,9 +6324,6 @@ intel_dp_hpd_pulse(struct intel_digital_port
> *intel_dig_port, bool long_hpd)
>  		return IRQ_NONE;
>  	}
>  
> -	wakeref = intel_display_power_get(dev_priv,
> -					  intel_aux_power_domain(intel_
> dig_port));
> -
>  	if (intel_dp->is_mst) {
>  		if (intel_dp_check_mst_status(intel_dp) == -EINVAL) {
>  			/*
> @@ -6341,7 +6335,8 @@ intel_dp_hpd_pulse(struct intel_digital_port
> *intel_dig_port, bool long_hpd)
>  			intel_dp->is_mst = false;
>  			drm_dp_mst_topology_mgr_set_mst(&intel_dp-
> >mst_mgr,
>  							intel_dp-
> >is_mst);
> -			goto put_power;
> +
> +			return IRQ_NONE;
>  		}
>  	}
>  
> @@ -6351,17 +6346,10 @@ intel_dp_hpd_pulse(struct intel_digital_port
> *intel_dig_port, bool long_hpd)
>  		handled = intel_dp_short_pulse(intel_dp);
>  
>  		if (!handled)
> -			goto put_power;
> +			return IRQ_NONE;
>  	}
>  
> -	ret = IRQ_HANDLED;
> -
> -put_power:
> -	intel_display_power_put(dev_priv,
> -				intel_aux_power_domain(intel_dig_port),
> -				wakeref);
> -
> -	return ret;
> +	return IRQ_HANDLED;
>  }
>  
>  /* check the VBT to see whether the eDP is on another port */

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