[PATCH v2 1/4] drm/i915: Read HDCP R0 thrice in case of mismatch

[Sean Paul]

On Thu, Mar 29, 2018 at 07:39:05PM +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.
> 
> Signed-off-by: Ramalingam C <ramalingam.c at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdcp.c | 30 +++++++++++++++++++-----------
>  1 file changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
> index 14ca5d3057a7..96b9025dc759 100644
> --- a/drivers/gpu/drm/i915/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
> @@ -496,9 +496,11 @@ static int intel_hdcp_auth(struct intel_digital_port *intel_dig_port,
>  	}
>  
>  	/*
> -	 * Wait for R0' to become available. The spec says 100ms from Aksv, but
> -	 * some monitors can take longer than this. We'll set the timeout at
> -	 * 300ms just to be sure.
> +	 * Wait for R0' to become available. The spec says minimum 100ms from
> +	 * Aksv, but some monitors can take longer than this. So we are
> +	 * combinely waiting for 300mSec just to be sure in case of HDMI.
> +	 * DP HDCP Spec mandates the two more reattempt to read R0, incase
> +	 * of R0 mismatch.

I am sorry to nitpick comments, but this doesn't belong here. Leave this comment
alone and add the part about the DP spec requiring retries directly above the
loop where we're actually doing the retries.

Sean

>  	 *
>  	 * On DP, there's an R0_READY bit available but no such bit
>  	 * exists on HDMI. Since the upper-bound is the same, we'll just do
> @@ -506,15 +508,21 @@ 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;
> +	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)) {
> +		/* 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