[Intel-gfx] [PATCH] drm/i915: Splitting intel_dp_check_link_status

[Lukas Wunner]

Hi,

On Mon, Jan 18, 2016 at 04:22:19PM +0530, Shubhangi Shrivastava wrote:
> When created originally intel_dp_check_link_status()
> was supposed to handle only link training for short
> pulse but has grown into handler for short pulse itself.
> This patch cleans up this function by splitting it into
> two halves. First intel_dp_short_pulse() is called,
> which will be entry point and handle all logic for
> short pulse handling while intel_dp_check_link_status()
> will retain its original purpose of only doing link
> status related work.
> The link retraining part when EQ is not correct is
> retained to intel_dp_check_link_status whereas other
> operations are handled as part of intel_dp_short_pulse.
> This change is required to avoid performing all DPCD
> related operations on performing link retraining.
> 
> v2: Added WARN_ON to intel_dp_check_link_status()
>     Removed a call to intel_dp_get_link_status() (Ander)
> 
> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu at intel.com>
> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani at intel.com>
> Signed-off-by: Shubhangi Shrivastava <shubhangi.shrivastava at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 65 +++++++++++++++++++++++------------------
>  1 file changed, 36 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 82ee18d..f8d9611 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4279,6 +4279,36 @@ go_again:
>  	return -EINVAL;
>  }
>  
> +static void
> +intel_dp_check_link_status(struct intel_dp *intel_dp)
> +{
> +	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> +	struct drm_device *dev = intel_dp_to_dev(intel_dp);
> +	u8 link_status[DP_LINK_STATUS_SIZE];
> +
> +	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
> +
> +	if (!intel_dp_get_link_status(intel_dp, link_status)) {
> +		DRM_ERROR("Failed to get link status\n");
> +		return;
> +	}
> +
> +	if (!intel_encoder->base.crtc)
> +		return;
> +
> +	if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> +		return;

Why do you change the order of the three if-clauses above?
The original order seems to make more sense. (Checking for
->base.crtc and ->active is cheap, whereas accessing AUX to
get the link status is time consuming. You don't want to
spend that time only to bail out, should one of the other two
if-clauses fail.)

Best regards,

Lukas

> +
> +	/* if link training is requested we should perform it always */
> +	if ((intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) ||
> +		(!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {
> +		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
> +				intel_encoder->base.name);
> +		intel_dp_start_link_train(intel_dp);
> +		intel_dp_stop_link_train(intel_dp);
> +	}
> +}
> +
>  /*
>   * According to DP spec
>   * 5.1.2:
> @@ -4288,14 +4318,10 @@ go_again:
>   *  4. Check link status on receipt of hot-plug interrupt
>   */
>  static void
> -intel_dp_check_link_status(struct intel_dp *intel_dp)
> +intel_dp_short_pulse(struct intel_dp *intel_dp)
>  {
>  	struct drm_device *dev = intel_dp_to_dev(intel_dp);
> -	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
>  	u8 sink_irq_vector;
> -	u8 link_status[DP_LINK_STATUS_SIZE];
> -
> -	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
>  
>  	/*
>  	 * Clearing compliance test variables to allow capturing
> @@ -4305,17 +4331,6 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
>  	intel_dp->compliance_test_type = 0;
>  	intel_dp->compliance_test_data = 0;
>  
> -	if (!intel_encoder->base.crtc)
> -		return;
> -
> -	if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> -		return;
> -
> -	/* Try to read receiver status if the link appears to be up */
> -	if (!intel_dp_get_link_status(intel_dp, link_status)) {
> -		return;
> -	}
> -
>  	/* Now read the DPCD to see if it's actually running */
>  	if (!intel_dp_get_dpcd(intel_dp)) {
>  		return;
> @@ -4335,14 +4350,9 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
>  			DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
>  	}
>  
> -	/* if link training is requested we should perform it always */
> -	if ((intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) ||
> -		(!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {
> -		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
> -			      intel_encoder->base.name);
> -		intel_dp_start_link_train(intel_dp);
> -		intel_dp_stop_link_train(intel_dp);
> -	}
> +	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> +	intel_dp_check_link_status(intel_dp);
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
>  }
>  
>  /* XXX this is probably wrong for multiple downstream ports */
> @@ -5072,11 +5082,8 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
>  			}
>  		}
>  
> -		if (!intel_dp->is_mst) {
> -			drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> -			intel_dp_check_link_status(intel_dp);
> -			drm_modeset_unlock(&dev->mode_config.connection_mutex);
> -		}
> +		if (!intel_dp->is_mst)
> +			intel_dp_short_pulse(intel_dp);
>  	}
>  
>  	ret = IRQ_HANDLED;
> -- 
> 2.6.1
> 
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