Re: [PATCH v2 2/4] drm/i915: Read Vprime thrice incase of mismatch

[Sean Paul <seanpaul@chromium.org>]

On Thu, Mar 29, 2018 at 07:39:06PM +0530, Ramalingam C wrote:
> In case of V prime mismatch, DP HDCP spec mandates the re-read of
> Vprime atleast twice.
> 
> This patch needed for DP HDCP1.4 CTS Test: 1B-05.
> 
> v2:
>   Moved the V' validation into a function for retry. [Sean Paul]
> 
> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdcp.c | 113 +++++++++++++++++++++++---------------
>  1 file changed, 70 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
> index 96b9025dc759..f77d956b2b18 100644
> --- a/drivers/gpu/drm/i915/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
> @@ -142,53 +142,17 @@ bool intel_hdcp_is_ksv_valid(u8 *ksv)
>  	return true;
>  }
>  
> -/* Implements Part 2 of the HDCP authorization procedure */
> -static
> -int intel_hdcp_auth_downstream(struct intel_digital_port *intel_dig_port,
> -			       const struct intel_hdcp_shim *shim)
> +static inline

Why inline?

> +int intel_hdcp_validate_v_prime(struct intel_digital_port *intel_dig_port,
> +				const struct intel_hdcp_shim *shim,
> +				u8 *ksv_fifo, u8 num_downstream, u8 *bstatus)
>  {
>  	struct drm_i915_private *dev_priv;
>  	u32 vprime, sha_text, sha_leftovers, rep_ctl;
> -	u8 bstatus[2], num_downstream, *ksv_fifo;
>  	int ret, i, j, sha_idx;
>  
>  	dev_priv = intel_dig_port->base.base.dev->dev_private;
>  
> -	ret = intel_hdcp_poll_ksv_fifo(intel_dig_port, shim);
> -	if (ret) {
> -		DRM_ERROR("KSV list failed to become ready (%d)\n", ret);
> -		return ret;
> -	}
> -
> -	ret = shim->read_bstatus(intel_dig_port, bstatus);
> -	if (ret)
> -		return ret;
> -
> -	if (DRM_HDCP_MAX_DEVICE_EXCEEDED(bstatus[0]) ||
> -	    DRM_HDCP_MAX_CASCADE_EXCEEDED(bstatus[1])) {
> -		DRM_ERROR("Max Topology Limit Exceeded\n");
> -		return -EPERM;
> -	}
> -
> -	/*
> -	 * When repeater reports 0 device count, HDCP1.4 spec allows disabling
> -	 * the HDCP encryption. That implies that repeater can't have its own
> -	 * display. As there is no consumption of encrypted content in the
> -	 * repeater with 0 downstream devices, we are failing the
> -	 * authentication.
> -	 */
> -	num_downstream = DRM_HDCP_NUM_DOWNSTREAM(bstatus[0]);
> -	if (num_downstream == 0)
> -		return -EINVAL;
> -
> -	ksv_fifo = kzalloc(num_downstream * DRM_HDCP_KSV_LEN, GFP_KERNEL);
> -	if (!ksv_fifo)
> -		return -ENOMEM;
> -
> -	ret = shim->read_ksv_fifo(intel_dig_port, num_downstream, ksv_fifo);
> -	if (ret)
> -		return ret;
> -
>  	/* Process V' values from the receiver */
>  	for (i = 0; i < DRM_HDCP_V_PRIME_NUM_PARTS; i++) {
>  		ret = shim->read_v_prime_part(intel_dig_port, i, &vprime);
> @@ -353,7 +317,7 @@ int intel_hdcp_auth_downstream(struct intel_digital_port *intel_dig_port,
>  			return ret;
>  		sha_idx += sizeof(sha_text);
>  	} else {
> -		DRM_ERROR("Invalid number of leftovers %d\n", sha_leftovers);
> +		DRM_DEBUG("Invalid number of leftovers %d\n", sha_leftovers);
>  		return -EINVAL;
>  	}
>  
> @@ -381,14 +345,77 @@ int intel_hdcp_auth_downstream(struct intel_digital_port *intel_dig_port,
>  	if (intel_wait_for_register(dev_priv, HDCP_REP_CTL,
>  				    HDCP_SHA1_COMPLETE,
>  				    HDCP_SHA1_COMPLETE, 1)) {
> -		DRM_ERROR("Timed out waiting for SHA1 complete\n");
> +		DRM_DEBUG("Timed out waiting for SHA1 complete\n");
>  		return -ETIMEDOUT;
>  	}
>  	if (!(I915_READ(HDCP_REP_CTL) & HDCP_SHA1_V_MATCH)) {
> -		DRM_ERROR("SHA-1 mismatch, HDCP failed\n");
> +		DRM_DEBUG("SHA-1 mismatch, HDCP failed\n");

I think the DEBUG should be DEBUG_KMS, consistent with the rest of the file?

>  		return -ENXIO;
>  	}
>  
> +	return 0;
> +}
> +
> +/* Implements Part 2 of the HDCP authorization procedure */
> +static
> +int intel_hdcp_auth_downstream(struct intel_digital_port *intel_dig_port,
> +			       const struct intel_hdcp_shim *shim)
> +{
> +	u8 bstatus[2], num_downstream, *ksv_fifo;
> +	int ret, i, tries = 3;
> +
> +	ret = intel_hdcp_poll_ksv_fifo(intel_dig_port, shim);
> +	if (ret) {
> +		DRM_ERROR("KSV list failed to become ready (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	ret = shim->read_bstatus(intel_dig_port, bstatus);
> +	if (ret)
> +		return ret;
> +
> +	if (DRM_HDCP_MAX_DEVICE_EXCEEDED(bstatus[0]) ||
> +	    DRM_HDCP_MAX_CASCADE_EXCEEDED(bstatus[1])) {
> +		DRM_ERROR("Max Topology Limit Exceeded\n");
> +		return -EPERM;
> +	}
> +
> +	/*
> +	 * When repeater reports 0 device count, HDCP1.4 spec allows disabling
> +	 * the HDCP encryption. That implies that repeater can't have its own
> +	 * display. As there is no consumption of encrypted content in the
> +	 * repeater with 0 downstream devices, we are failing the
> +	 * authentication.
> +	 */
> +	num_downstream = DRM_HDCP_NUM_DOWNSTREAM(bstatus[0]);
> +	if (num_downstream == 0)
> +		return -EINVAL;
> +
> +	ksv_fifo = kzalloc(num_downstream * DRM_HDCP_KSV_LEN, GFP_KERNEL);
> +	if (!ksv_fifo)
> +		return -ENOMEM;
> +
> +	ret = shim->read_ksv_fifo(intel_dig_port, num_downstream, ksv_fifo);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * When V prime mismatches, DP Spec mandates re-read of
> +	 * V prime atleast twice.
> +	 */
> +	for (i = 0; i < tries; i++) {
> +		ret = intel_hdcp_validate_v_prime(intel_dig_port, shim,
> +						  ksv_fifo, num_downstream,
> +						  bstatus);
> +		if (!ret)
> +			break;
> +	}
> +
> +	if (i == tries) {
> +		DRM_ERROR("V Prime validation failed.(%d)\n", ret);
> +		return ret;
> +	}
> +
>  	DRM_DEBUG_KMS("HDCP is enabled (%d downstream devices)\n",
>  		      num_downstream);
>  	return 0;
> -- 
> 2.7.4
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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