Re: [PATCH v2 4/8] drm/i915: Retry HDCP bksv read

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On Sat, Feb 03, 2018 at 01:41:32AM +0530, Ramalingam C wrote:
> HDCP specification says that when bksv is identified as invalid
> (not with 20 1s), bksv should be re-read and verified.
> 
> This patch adds the above mentioned re-read for bksv.
> 
> v2:
>   Rephrased the commit msg [Seanpaul]
> 
> Signed-off-by: Ramalingam C <ramalingam.c@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/intel_hdcp.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
> index cfd13ee8c534..40d0c5e73cc6 100644
> --- a/drivers/gpu/drm/i915/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
> @@ -397,7 +397,7 @@ static int intel_hdcp_auth(struct intel_digital_port *intel_dig_port,
>  	struct drm_i915_private *dev_priv;
>  	enum port port;
>  	unsigned long r0_prime_gen_start;
> -	int ret, i;
> +	int ret, i, retry = 1;
>  	union {
>  		u32 reg[2];
>  		u8 shim[DRM_HDCP_AN_LEN];
> @@ -438,11 +438,16 @@ static int intel_hdcp_auth(struct intel_digital_port *intel_dig_port,
>  	r0_prime_gen_start = jiffies;
>  
>  	memset(&bksv, 0, sizeof(bksv));
> -	ret = shim->read_bksv(intel_dig_port, bksv.shim);
> +
> +	do {
> +		ret = shim->read_bksv(intel_dig_port, bksv.shim);
> +		if (!ret)
> +			if (!intel_hdcp_is_ksv_valid(bksv.shim))
> +				ret = -ENODEV;
> +	} while (ret && retry--);

I think you missed the second part of my review. I'd really like to clean this
part up as well to make it a bit more straightforward.

Sean

> +
>  	if (ret)
>  		return ret;
> -	else if (!intel_hdcp_is_ksv_valid(bksv.shim))
> -		return -ENODEV;
>  
>  	I915_WRITE(PORT_HDCP_BKSVLO(port), bksv.reg[0]);
>  	I915_WRITE(PORT_HDCP_BKSVHI(port), bksv.reg[1]);
> -- 
> 2.7.4
> 

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