Re: Writing socketCAN module for my own hardware

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

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On 10/01/2014 09:26 AM, Florian Feldbauer wrote:
> I still have some problems with the socket CAN driver for
> my Raspberry Pi CAN interface.
> I added a printk statement in the read/write register functions to
> see what happens.
> 
> Looking into the output of `dmesg` after loading the kernel module
> I see in an endless loop appearing the lines
> 
> [  129.210361] sja1000_raspi: Read register 0: 0x21
> [  129.210394] sja1000_raspi: Write register 4: 0x00
> [  129.210423] sja1000_raspi sja1000_raspi.0 can0: bit-timing not yet
> defined
> 
> Is this an expected behavior?

Do you have network manager or a similar program running that is trying
to handle the CAN interface?

> After setting the bitrate using
> $> ip link set can0 type can bitrate 250000
> The above messages stop.
> 
> dmesg output at this point:
> [  172.870195] sja1000_raspi: Read register 15: 0xff
> [  172.870231] sja1000_raspi: Read register 14: 0xff
> [  172.872933] sja1000_raspi sja1000_raspi.0 can0: setting BTR0=0x01
> BTR1=0x1c
> [  172.872971] sja1000_raspi: Write register 6: 0x01
> [  172.872987] sja1000_raspi: Write register 7: 0x1c
> [  173.269190] sja1000_raspi: Read register 0: 0x21
> [  173.269221] sja1000_raspi: Write register 4: 0x00
> [  173.269287] sja1000_raspi: Write register 15: 0x00
> [  173.269303] sja1000_raspi: Write register 14: 0x00
> [  173.269319] sja1000_raspi: Read register 12: 0xff
> [  173.269336] sja1000_raspi: Read register 0: 0x21
> [  173.269348] sja1000_raspi: Write register 0: 0x00
> [  173.269369] sja1000_raspi: Read register 0: 0x20
> [  173.269381] sja1000_raspi: Write register 4: 0x7f
> [  173.269446] sja1000_raspi: Read register 15: 0x0c
> [  173.269462] sja1000_raspi: Read register 14: 0x03
> 
> The main problem is: If I now try to change the bitrate again
> I get a "Device or resource busy" error.

You'll get this busy error if the device is still "up", so there is
someone who automatically does something similar to "ifconfig can0 up".

> demsg shows in this case simply these to lines:
> [  445.848207] sja1000_raspi: Read register 15: 0x0c
> [  445.848241] sja1000_raspi: Read register 14: 0x03
> 
> After bringing the interface up and trying to listen on the CANbus
> using candump from the can-utils I get nothing, although a second
> node is sending frames and bitrate settings are correct.

Do you get any interrupts?

> I'm working with the raspberry pi kernel
> (https://github.com/raspberrypi/linux)
> version 3.12.y commit c256eb9968c8997dce47350d2075e42f1b3991d3
> 
> Source of my own kernel module is also on github
> https://github.com/ffeldbauer/epics_RPi_can/blob/ver3.0.0/CAN_interface/driver/sja1000_raspi.c
> 
> 
> As written before, I could not find a documentation of socketCAN and
> simply tried
> to "copy" the sja1000_isa.c driver...naybe I did something completely
> wrong or missed
> something?

Yes, making a copy of the driver is probably not the right thing....
BTW: where's are the original copyright notes?

> Any help is very much appreciated!

regards,
Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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