linux-kernel - [PATCH AUTOSEL 6.8 07/28] thunderbolt: Calculate DisplayPort tunnel bandwidth after DPRX capabilities read

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Date: Wed,  3 Apr 2024 13:16:09 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Gil Fine <gil.fine@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Sasha Levin <sashal@...nel.org>,
	andreas.noever@...il.com,
	michael.jamet@...el.com,
	YehezkelShB@...il.com,
	linux-usb@...r.kernel.org
Subject: [PATCH AUTOSEL 6.8 07/28] thunderbolt: Calculate DisplayPort tunnel bandwidth after DPRX capabilities read

From: Gil Fine <gil.fine@...ux.intel.com>

[ Upstream commit ccd845021147dc8257a05ed8f5a7f9c61a9101e3 ]

According to USB4 Connection Manager guide, after DisplayPort tunnel was
setup, the DPRX capabilities read is performed by the DPTX. According to
VESA spec, this shall be completed within 5 seconds after the DisplayPort
tunnel was setup. Hence, if the bit: DPRX Capabilities Read Done, was
not set to '1' by this time, we timeout and fail calculating DisplayPort
tunnel consumed bandwidth.

Signed-off-by: Gil Fine <gil.fine@...ux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/thunderbolt/tunnel.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 6fffb2c82d3d1..4f09216b70f90 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -1196,17 +1196,13 @@ static int tb_dp_consumed_bandwidth(struct tb_tunnel *tunnel, int *consumed_up,
 		/*
 		 * Then see if the DPRX negotiation is ready and if yes
 		 * return that bandwidth (it may be smaller than the
-		 * reduced one). Otherwise return the remote (possibly
-		 * reduced) caps.
+		 * reduced one). According to VESA spec, the DPRX
+		 * negotiation shall compete in 5 seconds after tunnel
+		 * established. We give it 100ms extra just in case.
 		 */
-		ret = tb_dp_wait_dprx(tunnel, 150);
-		if (ret) {
-			if (ret == -ETIMEDOUT)
-				ret = tb_dp_read_cap(tunnel, DP_REMOTE_CAP,
-						     &rate, &lanes);
-			if (ret)
-				return ret;
-		}
+		ret = tb_dp_wait_dprx(tunnel, 5100);
+		if (ret)
+			return ret;
 		ret = tb_dp_read_cap(tunnel, DP_COMMON_CAP, &rate, &lanes);
 		if (ret)
 			return ret;
-- 
2.43.0