Re: mcp251x can't drop the can0 Interface

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 02/07/2014 09:12 PM, John Whitmore wrote:
> I guess you might say that I'm playing with an MCP2515 connected to a
> RaspberryPi. I've got a problem which I've asked about on the RaspberryPi
> forum but have never received an answer, so as a last resort I thought I'd try
> here.
> 
> Basically I bring up the MCP2515 in listen mode at a certain baud rate. I
> wanted to work on auto detetection of baud rate. So after listening for a
> period of time at a certain baud rate I try to change the baud rate but I
> can't do that with the linux mcp251x driver (I don't think it's the driver's
> fault but have no idea whose it is). I've put in some debug statements
> to see what happens when I execute "ifconfig can0 down" and basically the
> interface goes down momentarily and then gets brough straight back up
> again. So when I try to use the "ip" command to set the new baud rate I get an
> error that the device is busy. 

Please add this patch to the driver:

-------->8-------->8-------->8-------->8-------->8-------->8-------->8--------
diff --git a/drivers/net/can/mcp251x.c b/drivers/net/can/mcp251x.c
index cdb9808..b1ea15c 100644
--- a/drivers/net/can/mcp251x.c
+++ b/drivers/net/can/mcp251x.c
@@ -697,6 +697,8 @@ static int mcp251x_stop(struct net_device *net)
        struct mcp251x_priv *priv = netdev_priv(net);
        struct spi_device *spi = priv->spi;

+       dump_stack();
+
        close_candev(net);

        priv->force_quit = 1;
@@ -941,6 +943,8 @@ static int mcp251x_open(struct net_device *net)
        unsigned long flags = IRQF_ONESHOT | IRQF_TRIGGER_FALLING;
        int ret;

+       dump_stack();
+
        ret = open_candev(net);
        if (ret) {
                dev_err(&spi->dev, "unable to set initial baudrate!\n");

-------->8-------->8-------->8-------->8-------->8-------->8-------->8--------

Then reproduce your problem, then send dmesg output.

Marc

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