linux-kernel - [PATCH AUTOSEL 4.14 3/4] can: mcba_usb: Fix termination command argument

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Message-Id: <20230629190225.908451-3-sashal@kernel.org>
Date:   Thu, 29 Jun 2023 15:02:23 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yasushi SHOJI <yasushi.shoji@...il.com>,
        Yasushi SHOJI <yashi@...cecubics.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Sasha Levin <sashal@...nel.org>, wg@...ndegger.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, mailhol.vincent@...adoo.fr,
        socketcan@...tkopp.net, linux-can@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 3/4] can: mcba_usb: Fix termination command argument

From: Yasushi SHOJI <yasushi.shoji@...il.com>

[ Upstream commit 1a8e3bd25f1e789c8154e11ea24dc3ec5a4c1da0 ]

Microchip USB Analyzer can activate the internal termination resistors
by setting the "termination" option ON, or OFF to to deactivate them.
As I've observed, both with my oscilloscope and captured USB packets
below, you must send "0" to turn it ON, and "1" to turn it OFF.

>From the schematics in the user's guide, I can confirm that you must
drive the CAN_RES signal LOW "0" to activate the resistors.

Reverse the argument value of usb_msg.termination to fix this.

These are the two commands sequence, ON then OFF.

> No.     Time           Source                Destination           Protocol Length Info
>       1 0.000000       host                  1.3.1                 USB      46     URB_BULK out
>
> Frame 1: 46 bytes on wire (368 bits), 46 bytes captured (368 bits)
> USB URB
> Leftover Capture Data: a80000000000000000000000000000000000a8
>
> No.     Time           Source                Destination           Protocol Length Info
>       2 4.372547       host                  1.3.1                 USB      46     URB_BULK out
>
> Frame 2: 46 bytes on wire (368 bits), 46 bytes captured (368 bits)
> USB URB
> Leftover Capture Data: a80100000000000000000000000000000000a9

Signed-off-by: Yasushi SHOJI <yashi@...cecubics.com>
Link: https://lore.kernel.org/all/20221124152504.125994-1-yashi@spacecubics.com
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/can/usb/mcba_usb.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
index f7c3fc3dabfe4..01ef5cabdc11e 100644
--- a/drivers/net/can/usb/mcba_usb.c
+++ b/drivers/net/can/usb/mcba_usb.c
@@ -58,6 +58,10 @@
 #define MCBA_VER_REQ_USB 1
 #define MCBA_VER_REQ_CAN 2
 
+/* Drive the CAN_RES signal LOW "0" to activate R24 and R25 */
+#define MCBA_VER_TERMINATION_ON 0
+#define MCBA_VER_TERMINATION_OFF 1
+
 #define MCBA_SIDL_EXID_MASK 0x8
 #define MCBA_DLC_MASK 0xf
 #define MCBA_DLC_RTR_MASK 0x40
@@ -480,7 +484,7 @@ static void mcba_usb_process_ka_usb(struct mcba_priv *priv,
 		priv->usb_ka_first_pass = false;
 	}
 
-	if (msg->termination_state)
+	if (msg->termination_state == MCBA_VER_TERMINATION_ON)
 		priv->can.termination = MCBA_TERMINATION_ENABLED;
 	else
 		priv->can.termination = MCBA_TERMINATION_DISABLED;
@@ -800,9 +804,9 @@ static int mcba_set_termination(struct net_device *netdev, u16 term)
 	};
 
 	if (term == MCBA_TERMINATION_ENABLED)
-		usb_msg.termination = 1;
+		usb_msg.termination = MCBA_VER_TERMINATION_ON;
 	else
-		usb_msg.termination = 0;
+		usb_msg.termination = MCBA_VER_TERMINATION_OFF;
 
 	mcba_usb_xmit_cmd(priv, (struct mcba_usb_msg *)&usb_msg);
 
-- 
2.39.2