Re: [PATCH 10/12] drm/i915: Update link training automated test function for Displayport compliance

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Jul 14, 2014 at 12:10:45PM -0700, Todd Previte wrote:
> Implements basic link training functionality for Displayport automated compliance
> testing.
> 
> Signed-off-by: Todd Previte <tprevite@gmail.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 47 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 65830e9..e4b31ad 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3427,6 +3427,53 @@ static uint8_t
>  intel_dp_autotest_link_training(struct intel_dp *intel_dp)
>  {
>  	uint8_t test_result = DP_TEST_NAK;
> +	uint8_t rxdata[2];
> +	uint8_t link_status[DP_LINK_STATUS_SIZE];
> +	int bytes_ret = 0;
> +	struct drm_connector *connector = &intel_dp->attached_connector->base;
> +	struct intel_digital_port *intel_dig_port =
> +		enc_to_dig_port(&intel_dp->attached_connector->encoder->base);
> +
> +	/* Read test parameters */
> +	bytes_ret = drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_LINK_RATE, rxdata, 2);
> +
> +	/* Set link rate directly */
> +	intel_dp->link_bw = rxdata[0];
> +	/* Preserve 7:5 when setting lane count */
> +	intel_dp->lane_count &= 0xE0;
> +	intel_dp->lane_count |= rxdata[1];

This won't work - if you change the link config you need to do a full
recomputation of the modeset config and a full modeset. No, we dont (yet)
have the infrastructure for this, which is why dp is such a pain since we
can change the link config once we've decided on something :(
-Daniel

> +
> +	DRM_DEBUG_KMS("Displayport: Link training testing - %d lanes @ %02x link rate\n",
> +			intel_dp->lane_count, intel_dp->link_bw);
> +
> +	/* Train the link */
> +	intel_dp->DP = intel_dig_port->saved_port_bits |
> +					DDI_BUF_CTL_ENABLE |
> +					DDI_BUF_EMP_400MV_0DB_HSW;
> +	intel_dp->DP |= DDI_PORT_WIDTH(intel_dp->lane_count);
> +
> +	if (!intel_dp_start_link_train(intel_dp)) {
> +		DRM_DEBUG_KMS("Displayport: intel_dp_start_link_train() failed\n");
> +		test_result = false;
> +	}
> +	if (!intel_dp_complete_link_train(intel_dp)) {
> +		DRM_DEBUG_KMS("Displayport: intel_dp_complete_link_train() failed\n");
> +		test_result = false;
> +	}
> +	if (!intel_dp_stop_link_train(intel_dp)) {
> +		DRM_DEBUG_KMS("Displayport: intel_dp_stop_link_train() failed\n");
> +		test_result = false;
> +	}
> +
> +	/* Check link status for successful completion */
> +	if (drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))
> +		test_result = true;
> +
> +	if (test_result == false) {
> +		/* Clear link training here */
> +		intel_dp_set_idle_link_train(intel_dp);
> +	}
> +
>  	return test_result;
>  }
>  
> -- 
> 1.9.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch