linux-kernel - [PATCH] drm/bridge: it6505: fix HDCP V match check is not performed correctly

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Message-Id: <20250108-fix-hdcp-v-comp-v1-1-9404811825cd@ite.com.tw>
Date: Wed, 08 Jan 2025 13:45:14 +0800
From: Hermes Wu via B4 Relay <devnull+Hermes.wu.ite.com.tw@...nel.org>
To: 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>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, 
 Hermes Wu <hermes.wu@....com.tw>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Pet.Weng@....com.tw, Kenneth.Hung@....com.tw, treapking@...omium.org, 
 Hermes Wu <Hermes.wu@....com.tw>
Subject: [PATCH] drm/bridge: it6505: fix HDCP V match check is not
 performed correctly

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

The loop of V compare is expected to iterate for 5 times
which compare V array form av[0][] to av[4][].
It should check loop counter reach the last statement before return true

Fixes: 0989c02c7a5c ("drm/bridge: it6505: fix HDCP CTS compare V matching")

Signed-off-by: Hermes Wu <Hermes.wu@....com.tw>
---
 drivers/gpu/drm/bridge/ite-it6505.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index 88ef76a37fe6accacdd343839ff2569b31b18ceb..e87247aea1d2ffbdad192e241056d34fdfb32163 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -2254,9 +2254,12 @@ static bool it6505_hdcp_part2_ksvlist_check(struct it6505 *it6505)
 			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;
-
-			DRM_DEV_DEBUG_DRIVER(dev, "V' all match!! %d, %d", retry, i);
-			return true;
+			if (i == 4) {
+				DRM_DEV_DEBUG_DRIVER(dev,
+						     "V' all match!! %d",
+						     retry);
+				return true;
+			}
 		}
 	}
 

---
base-commit: 938fbb16aba8f7b88e0fdcf56f315a5bbad41aad
change-id: 20250107-fix-hdcp-v-comp-3ba8e3d7adf3

Best regards,
-- 
Hermes Wu <Hermes.wu@....com.tw>