Re: [PATCH 1/5] drm/i915: Add support for DP link training compliance

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

On Tue, 22 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> This patch adds support to handle automated DP compliance
> link training test requests. This patch has been tested with
> Unigraf DPR-120 DP Compliance device for testing Link
> Training Compliance.
> After we get a short pulse Compliance test request, test
> request values are read and hotplug uevent is sent in order
> to trigger another modeset during which the pipe is configured
> and link is retrained and enabled for link parameters requested
> by the test.
>
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 73 ++++++++++++++++++++++++++++++++++++----
>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>  2 files changed, 69 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 90283ed..69944d1 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -288,6 +288,21 @@ static int intel_dp_common_rates(struct intel_dp *intel_dp,
>  			       common_rates);
>  }
>  
> +static int intel_dp_link_rate_index(struct intel_dp *intel_dp,
> +				    int *common_rates, int link_rate)
> +{
> +	int common_len;
> +	int index;
> +
> +	common_len = intel_dp_common_rates(intel_dp, common_rates);
> +	for (index = 0; index < common_len; index++) {
> +		if (link_rate == common_rates[common_len - index - 1])
> +			return common_len - index - 1;
> +	}
> +
> +	return -1;
> +}
> +
>  static enum drm_mode_status
>  intel_dp_mode_valid(struct drm_connector *connector,
>  		    struct drm_display_mode *mode)
> @@ -1554,6 +1569,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  	/* Conveniently, the link BW constants become indices with a shift...*/
>  	int min_clock = 0;
>  	int max_clock;
> +	int link_rate_index;
>  	int bpp, mode_rate;
>  	int link_avail, link_clock;
>  	int common_rates[DP_MAX_SUPPORTED_RATES] = {};
> @@ -1595,6 +1611,16 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return false;
>  
> +	/* Use values requested by Compliance Test Request */
> +	if (intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING) {
> +			link_rate_index = intel_dp_link_rate_index(intel_dp,
> +								   common_rates,
> +								   drm_dp_bw_code_to_link_rate(intel_dp->compliance_test_link_rate));
> +			if (link_rate_index >= 0)
> +				min_clock = max_clock = link_rate_index;
> +			min_lane_count = max_lane_count = intel_dp->compliance_test_lane_count;

You need to be more strict about validating
compliance_test_lane_count. You do mask it with DP_MAX_LANE_COUNT_MASK,
but that's 0x1f, quite a few more lanes than we have...

> +	}
> +
>  	DRM_DEBUG_KMS("DP link computation with max lane count %i "
>  		      "max bw %d pixel clock %iKHz\n",
>  		      max_lane_count, common_rates[max_clock],
> @@ -1642,6 +1668,7 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
>  				}
>  			}
>  		}
> +

Please pay attention to not making unrelated changes.

>  	}
>  
>  	return false;
> @@ -3804,6 +3831,29 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
>  static uint8_t intel_dp_autotest_link_training(struct intel_dp *intel_dp)
>  {
>  	uint8_t test_result = DP_TEST_ACK;
> +	int status = 0;
> +	/* (DP CTS 1.2)
> +	 * 4.3.1.11
> +	 */
> +	/* Read the TEST_LANE_COUNT and TEST_LINK_RTAE fields (DP CTS 3.1.4) */
> +	status = drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_LANE_COUNT,
> +				  &intel_dp->compliance_test_lane_count);
> +
> +	if (status <= 0) {
> +		DRM_DEBUG_KMS("Could not read test lane count from "
> +			      "reference sink\n");

No need to be so verbose, DRM_DEBUG_KMS will include the function name,
so a simple "Lane count read failed" or something will suffice.

> +		return 0;

Should these return DP_TEST_NAK on errors or what?

> +	}
> +	intel_dp->compliance_test_lane_count &= DP_MAX_LANE_COUNT_MASK;
> +
> +	status = drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_LINK_RATE,
> +				   &intel_dp->compliance_test_link_rate);
> +	if (status <= 0) {
> +		DRM_DEBUG_KMS("Could not read test link rate from "
> +			      "refernce sink\n");

Ditto.

> +		return 0;
> +	}
> +
>  	return test_result;
>  }
>  
> @@ -3908,7 +3958,8 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
>  				   DP_TEST_RESPONSE,
>  				   &response, 1);
>  	if (status <= 0)
> -		DRM_DEBUG_KMS("Could not write test response to sink\n");
> +		DRM_DEBUG_KMS("Could not write test response "
> +			      "to sink\n");

Unrelated change, and one we don't want.

>  }
>  
>  static int
> @@ -4018,9 +4069,8 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
>  	if (WARN_ON_ONCE(!intel_dp->lane_count))
>  		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))) {
> +	/* Retrain if Channel EQ or CR not ok */
> +	if ((!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {

Too many braces.

>  		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
>  			      intel_encoder->base.name);
>  
> @@ -4045,6 +4095,7 @@ static void intel_dp_handle_test_request(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 = 0;
>  	u8 old_sink_count = intel_dp->sink_count;
>  	bool ret;
> @@ -4056,6 +4107,8 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
>  	intel_dp->compliance_test_active = 0;
>  	intel_dp->compliance_test_type = 0;
>  	intel_dp->compliance_test_data = 0;
> +	intel_dp->compliance_test_lane_count = 0;
> +	intel_dp->compliance_test_link_rate = 0;

Looks like compliance stuff should be a sub struct in intel_dp, and you
could just memset it to 0.

>  
>  	/*
>  	 * Now read the DPCD to see if it's actually running
> @@ -4079,8 +4132,9 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
>  				   DP_DEVICE_SERVICE_IRQ_VECTOR,
>  				   sink_irq_vector);
>  
> -		if (sink_irq_vector & DP_AUTOMATED_TEST_REQUEST)
> -			DRM_DEBUG_DRIVER("Test request in short pulse not handled\n");
> +		if (sink_irq_vector & DP_AUTOMATED_TEST_REQUEST) {
> +			intel_dp_handle_test_request(intel_dp);
> +		}

Unnecessary curly braces.

>  		if (sink_irq_vector & (DP_CP_IRQ | DP_SINK_SPECIFIC_IRQ))
>  			DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
>  	}
> @@ -4088,6 +4142,11 @@ static void intel_dp_handle_test_request(struct intel_dp *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);
> +	if ((intel_dp->compliance_test_type == DP_TEST_LINK_TRAINING)) {

Too many braces.

> +		DRM_DEBUG_KMS("Link Training Compliance Test requested\n");
> +		/* Send a Hotplug Uevent to userspace to start modeset */
> +		drm_kms_helper_hotplug_event(intel_encoder->base.dev);
> +	}
>  
>  	return true;
>  }
> @@ -4375,6 +4434,8 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  		intel_dp->compliance_test_active = 0;
>  		intel_dp->compliance_test_type = 0;
>  		intel_dp->compliance_test_data = 0;
> +		intel_dp->compliance_test_lane_count = 0;
> +		intel_dp->compliance_test_link_rate = 0;

Same thing about making compliance sub struct.

>  
>  		if (intel_dp->is_mst) {
>  			DRM_DEBUG_KMS("MST device may have disappeared %d vs %d\n",
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index cd132c2..1e88288 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -958,6 +958,8 @@ struct intel_dp {
>  	unsigned long compliance_test_type;
>  	unsigned long compliance_test_data;
>  	bool compliance_test_active;
> +	u8 compliance_test_lane_count;
> +	u8 compliance_test_link_rate;
>  };
>  
>  struct intel_lspcon {

-- 
Jani Nikula, Intel Open Source Technology Center
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