linux-kernel - Re: [PATCH] can: mcba_usb: Fix termination command argument

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Message-ID: <20221123223410.sg2ixkaqg4dpe7ew@pengutronix.de>
Date:   Wed, 23 Nov 2022 23:34:10 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Yasushi SHOJI <yasushi.shoji@...il.com>,
        Remigiusz Kołłątaj 
        <remigiusz.kollataj@...ica.com>
Cc:     Yasushi SHOJI <yashi@...cecubics.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] can: mcba_usb: Fix termination command argument

Let's take the original driver author into the loop.

On 24.11.2022 04:44:06, Yasushi SHOJI wrote:
> Microchip USB Analyzer can be set with termination setting ON or OFF.
> As I've observed, both with my oscilloscope and USB packet capture
> below, you must send "0" to turn it ON, and "1" to turn it OFF.
> 
> Reverse the argument value 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

Is this the USB data after applying the patch?

Can you measure the resistance between CAN-H and CAN-L to verify that
your patch fixes the problem?

> Signed-off-by: Yasushi SHOJI <yashi@...cecubics.com>
> ---
>  drivers/net/can/usb/mcba_usb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
> index 218b098b261d..67beff1a3876 100644
> --- a/drivers/net/can/usb/mcba_usb.c
> +++ b/drivers/net/can/usb/mcba_usb.c
> @@ -785,9 +785,9 @@ static int mcba_set_termination(struct net_device *netdev, u16 term)
>  	};
>  
>  	if (term == MCBA_TERMINATION_ENABLED)
> -		usb_msg.termination = 1;
> -	else
>  		usb_msg.termination = 0;
> +	else
> +		usb_msg.termination = 1;
>  
>  	mcba_usb_xmit_cmd(priv, (struct mcba_usb_msg *)&usb_msg);

What about the static void mcba_usb_process_ka_usb() function? Do you
need to convert this, too?

Marc

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