Re: [PATCH 3/6] drm/i915: Implement basic Displayport automated testing function for EDID operations

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

On Wed, 25 Jun 2014, Todd Previte <tprevite@gmail.com> wrote:
> Implements some of the basic EDID tests for Displayport compliance. These tests
> include reading the EDID, verifying the checksum and writing the test responses
> back to the sink device.
>
> Signed-off-by: Todd Previte <tprevite@gmail.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 36 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 43fcabe..d060853 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3352,8 +3352,42 @@ intel_dp_autotest_video_pattern(struct intel_dp *intel_dp)
>  static uint8_t
>  intel_dp_autotest_edid(struct intel_dp *intel_dp)
>  {
> +	struct drm_connector *connector = &intel_dp->attached_connector->base;
> +	struct i2c_adapter *adapter = &intel_dp->aux.ddc;
> +	struct edid *edid_read = NULL;
> +	uint8_t *edid_data = NULL;
>  	uint8_t test_result = DP_TEST_NAK;
> -	return test_result;
> +	uint32_t i = 0, ret = 0, checksum = 0;
> +	struct drm_display_mode *use_mode = NULL;
> +	dp_compliance_mode comp_mode_type = DP_COMPLIANCE_MODE_PREFERRED;
> +	int mode_count = 0;
> +
> +	edid_read = drm_get_edid(connector, adapter);
> +
> +	DRM_DEBUG_KMS("Displayport: EDID automated test\n");
> +
> +	if (edid_read) {

It is customary to have if (!edid_read) and bail out early. Then the
rest will be a happy day scenario with minimal indentation.

BR,
Jani.


> +		test_result = true;
> +		edid_data = (uint8_t*) edid_read;
> +		// Compute checksum
> +		for (i = 0; i < 128; i++)
> +				checksum += edid_data[i];
> +
> +		DRM_DEBUG_KMS("Displayport: EDID test - computed byte sum = %02x\n", checksum);
> +		// Verify EDID checksum
> +		if (checksum % 256 == 0) {
> +			/* Write the checksum to EDID checksum register */
> +			ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TEST_EDID_CHECKSUM, &edid_read->checksum, 1);
> +			// Reponse is ACK and and checksum written
> +			test_result = DP_TEST_ACK | DP_TEST_EDID_CHECKSUM_WRITE;
> +			DRM_DEBUG_KMS("Displayport: EDID test - checksum = %02x\n", edid_read->checksum);
> +		}
> +		else {
> +			// Invalid checksum, set for failsafe mode
> +			comp_mode_type = DP_COMPLIANCE_MODE_FAILSAFE;
> +		}
> +	}
> +        return test_result;
>  }
>  
>  /* Displayport compliance testing - PHY pattern testing */
> -- 
> 1.9.1
>
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-- 
Jani Nikula, Intel Open Source Technology Center