drm/i915: Retry HDCP bksv read

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]

v4:
  retry only if bksv is invalid and no error msg on each attempt
  [Seanpaul]

v5:
  Correcting the return value [Seanpaul].

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1517851922-30547-1-git-send-email-ramalingam.c@intel.com

diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
index cfd13ee..d7ddd6b 100644 (file)
--- 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 +438,19 @@ 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);
-       if (ret)
-               return ret;
-       else if (!intel_hdcp_is_ksv_valid(bksv.shim))
+
+       /* HDCP spec states that we must retry the bksv if it is invalid */
+       for (i = 0; i < 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 == tries) {
+               DRM_ERROR("HDCP failed, Bksv is invalid\n");
                return -ENODEV;
+       }
 
        I915_WRITE(PORT_HDCP_BKSVLO(port), bksv.reg[0]);
        I915_WRITE(PORT_HDCP_BKSVHI(port), bksv.reg[1]);