drm/bridge: it6505: fix HDCP CTS compare V matching

When HDCP negotiation with a repeater device.
Checking SHA V' matching must retry 3 times before restarting HDCP.

Signed-off-by: Hermes Wu <hermes.wu@ite.com.tw>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241230-v7-upstream-v7-8-e0fdd4844703@ite.corp-partner.google.com

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index 93e4c5c..e6badb2 100644 (file)
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -2058,7 +2058,7 @@ static bool it6505_hdcp_part2_ksvlist_check(struct it6505 *it6505)
 {
        struct device *dev = it6505->dev;
        u8 av[5][4], bv[5][4];
-       int i, err;
+       int i, err, retry;
 
        i = it6505_setup_sha1_input(it6505, it6505->sha1_input);
        if (i <= 0) {
@@ -2067,22 +2067,28 @@ static bool it6505_hdcp_part2_ksvlist_check(struct it6505 *it6505)
        }
 
        it6505_sha1_digest(it6505, it6505->sha1_input, i, (u8 *)av);
+       /*1B-05 V' must retry 3 times */
+       for (retry = 0; retry < 3; retry++) {
+               err = it6505_get_dpcd(it6505, DP_AUX_HDCP_V_PRIME(0), (u8 *)bv,
+                                     sizeof(bv));
 
-       err = it6505_get_dpcd(it6505, DP_AUX_HDCP_V_PRIME(0), (u8 *)bv,
-                             sizeof(bv));
+               if (err < 0) {
+                       dev_err(dev, "Read V' value Fail %d", retry);
+                       continue;
+               }
 
-       if (err < 0) {
-               dev_err(dev, "Read V' value Fail");
-               return false;
-       }
+               for (i = 0; i < 5; i++) {
+                       if (bv[i][3] != av[i][0] || bv[i][2] != av[i][1] ||
+                           av[i][1] != av[i][2] || bv[i][0] != av[i][3])
+                               break;
 
-       for (i = 0; i < 5; i++)
-               if (bv[i][3] != av[i][0] || bv[i][2] != av[i][1] ||
-                   bv[i][1] != av[i][2] || bv[i][0] != av[i][3])
-                       return false;
+                       DRM_DEV_DEBUG_DRIVER(dev, "V' all match!! %d, %d", retry, i);
+                       return true;
+               }
+       }
 
-       DRM_DEV_DEBUG_DRIVER(dev, "V' all match!!");
-       return true;
+       DRM_DEV_DEBUG_DRIVER(dev, "V' NOT match!! %d", retry);
+       return false;
 }
 
 static void it6505_hdcp_wait_ksv_list(struct work_struct *work)