linux-kernel - [PATCH v5 08/10] drm/bridge: it6505: fix HDCP CTS compare V matching

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Message-ID: <20241001064346.32269-4-Hermes.Wu@ite.com.tw>
Date: Tue, 1 Oct 2024 14:43:45 +0800
From: Hermes Wu <Hermes.Wu@....com.tw>
To: Pin-yen Lin <treapking@...omium.org>
CC: Kenneth Hung <Kenneth.hung@....com.tw>, Pet Weng <Pet.Weng@....com.tw>,
        Hermes Wu <Hermes.wu@....com.tw>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman
	<jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten
 Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard
	<mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        "open list:DRM DRIVERS"
	<dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 08/10] drm/bridge: it6505: fix HDCP CTS compare V matching

From: Hermes Wu <Hermes.wu@....com.tw>

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@....com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 32 +++++++++++++++++------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index 7ab0da7fd9d7..da0ac789b8a3 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -2057,7 +2057,7 @@ 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) {
@@ -2066,22 +2066,28 @@ 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)
-- 
2.34.1