On Sat, Feb 03, 2018 at 03:39:06AM +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]
>
> v3:
> do-while to for-loop [Seanpaul]
>
> Signed-off-by: Ramalingam C <ramalingam.c@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_hdcp.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
> index cfd13ee8c534..b1047dbf3393 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, tries = 2;
> union {
> u32 reg[2];
> u8 shim[DRM_HDCP_AN_LEN];
> @@ -438,11 +438,22 @@ 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);
> +
> + /* When bksv is invalid, HDCP spec expects a re-read for bksv */
> + for (i = 0; i < tries; i++) {
> + ret = shim->read_bksv(intel_dig_port, bksv.shim);
> + if (!ret) {
> + if (intel_hdcp_is_ksv_valid(bksv.shim)) {
> + break;
> + } else {
> + DRM_ERROR("Invalid BKSV\n");
> + ret = -ENODEV;
> + }
> + }
> + }
Hmm, this is different from what I proposed in a couple of ways:
- This will print an ERROR for each failed attempt, which I don't think is
needed
- If shim->read_bksv fails, we shouldn't need to retry. The retry here should
only catch invalid ksv. The shim implementation is responsible for retrying if
the link is prone to failure.
For a refresher, this is what I proposed in the first review (I added an error):
/* HDCP spec states that we must retry the bksv if it is invalid */
for (i = 0; i < bksv_tries; i++) {
ret = shim->read_bksv(intel_dig_port, bksv.shim);
if (ret)
return ret;
if (intel_hdcp_is_ksv_valid(bksv.shim))
break;
}
if (i == bksv_tries) {
DRM_ERROR("HDCP failed, Bksv is invalid\n");
return -ENODEV;
}
> +
> 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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