Re: [PATCH 3/5] drm/i915: Reorganizing intel_dp_check_link_status

[Ander Conselvan De Oliveira <conselvan2@gmail.com>]

On Tue, 2016-01-19 at 16:07 +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.
> 
> intel_dp_short_pulse: All existing code other than
> link status read and link training upon error status.
> 
> intel_dp_check_link_status:
> The link status should be read on short pulse
> irrespective of panel being enabled

Please also mention why we should do that. With that fixed, this is

Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>

>  or not so
> intel_dp_get_link_status() performs dpcd read first
> then based on crtc active / enabled it will
> perform the link training.
> 
> v2: Added WARN_ON to intel_dp_check_link_status()
>     Removed a call to intel_dp_get_link_status() (Ander)
> 
> v3: Changed commit message to explain need of link status
>     being read before performing encoder checks (Daniel)
> 
> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@intel.com>
> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
> Signed-off-by: Shubhangi Shrivastava <shubhangi.shrivastava@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;
> +
> +	/* 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;
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