[PATCH v4 1/4] drm/i915: Read HDCP R0 thrice in case of mismatch

[Sean Paul]

On Mon, Apr 02, 2018 at 05:20:22PM +0530, Ramalingam C wrote:
> As per DP spec when R0 mismatch is detected, HDCP source supported
> re-read the R0 atleast twice.
> 
> And For HDMI and DP minimum wait required for the R0 availability is
> 100mSec. So this patch changes the wait time to 100mSec but retries
> twice with the time interval of 100mSec for each attempt.
> 
> This patch is needed for DP HDCP1.4 CTS Test: 1A-06.
> 
> v2:
>   No Change
> v3:
>   Comment on R0 retry is moved closer to the code[Seanpaul]
> v4:
>   Removing unwanted noise introduced in v3.
> 
> Signed-off-by: Ramalingam C <ramalingam.c at intel.com>

Reviewed-by: Sean Paul <seanpaul at chromium.org>

> ---
>  drivers/gpu/drm/i915/intel_hdcp.c | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
> index 14ca5d3057a7..f2cf2e3acd3c 100644
> --- a/drivers/gpu/drm/i915/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
> @@ -506,15 +506,26 @@ static int intel_hdcp_auth(struct intel_digital_port *intel_dig_port,
>  	 */
>  	wait_remaining_ms_from_jiffies(r0_prime_gen_start, 300);
>  
> -	ri.reg = 0;
> -	ret = shim->read_ri_prime(intel_dig_port, ri.shim);
> -	if (ret)
> -		return ret;
> -	I915_WRITE(PORT_HDCP_RPRIME(port), ri.reg);
> +	tries = 3;
>  
> -	/* Wait for Ri prime match */
> -	if (wait_for(I915_READ(PORT_HDCP_STATUS(port)) &
> -		     (HDCP_STATUS_RI_MATCH | HDCP_STATUS_ENC), 1)) {
> +	/*
> +	 * DP HDCP Spec mandates the two more reattempt to read R0, incase
> +	 * of R0 mismatch.
> +	 */
> +	for (i = 0; i < tries; i++) {
> +		ri.reg = 0;
> +		ret = shim->read_ri_prime(intel_dig_port, ri.shim);
> +		if (ret)
> +			return ret;
> +		I915_WRITE(PORT_HDCP_RPRIME(port), ri.reg);
> +
> +		/* Wait for Ri prime match */
> +		if (!wait_for(I915_READ(PORT_HDCP_STATUS(port)) &
> +		    (HDCP_STATUS_RI_MATCH | HDCP_STATUS_ENC), 1))
> +			break;
> +	}
> +
> +	if (i == tries) {
>  		DRM_ERROR("Timed out waiting for Ri prime match (%x)\n",
>  			  I915_READ(PORT_HDCP_STATUS(port)));
>  		return -ETIMEDOUT;
> -- 
> 2.7.4
> 

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