imx6 CAN wakes up Linux immediately

[akbar123]

Hi,

I can wake Linux up using UART by enabling its wakeup capability:

    $ echo enabled > /sys/class/tty/ttymxc0/power/wakeup

I have put Linux into sleep using the following command:

    $ echo mem > /sys/power/state

then sending a character over UART when the Linux is in sleep to wake it up... This scenario works well.

I want to do the same with CAN, so I enable its wakeup capability:

    $ echo enabled > /sys/class/net/can0/device/power/wakeup

Then put Linux into sleep. It shows that Linux goes into sleep, but it immediately wakes up. I want Linux to be woken up upon the reception of a frame over CAN, just like the UART scenario

Hardware: apalis imx6D ixora v1.2

OS: Linux 5.4.91-33088-g8c05b31a44c3

Question: What could be the problem? How can I do that?

Thanks in advance

[igorpadykov]

Hi Asghar

one can try below procedure:

Connect two boards CAN port.

On one board A,

Listen to CAN port.
Enable CAN wakeup:

find /sys -name "wakeup" | grep -i can

e.g.

find /sys -name "wakeup"|grep -i can

/sys/devices/platform/soc/30800000.aips-bus/30a10000.can/power/wakeup

Get all CAN wakeup control points and enable wakeup:

e.g.

echo enabled > /sys/devices/platform/soc/30800000.aips-bus/30a10000.can/power/wakeup

<enable remaining CAN ports too>

Suspend the board:

echo mem > /sys/power/state

On the other board, send data to CAN port.

Then board A will wake up.

Best regards
igor

[akbar123]

I guess there might be some problem with driver

I tested two different Linux kernel versions available in Toradex Linux built with apalis_imx6_defconfig :

5.4: Linux goes to sleep and immediately wake up

4.9: Linux goes to sleep and does not wake up upon receiving a CAN frame

What kernel version do you use?

[igorpadykov]

may be suggested to try with NXP Sabre SD reference boards.

>What kernel version do you use?

nxp supports only official linux releases from source.codeaurora.org/external/imx/linux-imx repository
https://source.codeaurora.org/external/imx/linux-imx/tree/?h=imx_5.4.70_2.3.0

Documentation

https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applicat...

Best regards
igor

[akbar123 · Accepted solution]

I used NXP Linux kernel from https://source.codeaurora.org/external/imx/linux-imx and the problem fixed

$ git clone https://source.codeaurora.org/external/imx/linux-imx/

$ git checkout -b 4.19 remotes/origin/imx_4.19.35_1.1.0

$ make imx_v7_defconfig
$ make -j$(nproc) zImage
$ make imx6q-apalis-ixora-v1.1.dtb
$ make -j$(nproc) modules

Now I can put Linux into sleep and wake it up by sending a CAN frame to it:

Enable CAN wakeup feature:

$ cd /sys/devices/soc0/soc/2000000.aips-bus/2094000.flexcan/power

$ echo enabled > wakeup

Put Linux into sleep:

$ echo mem > /sys/power/state

Now, by using another board to send a CAN frame, I can wake up Linux

[akbar123]

It has the same result. Linux will go into sleep, BUT it immediately wakes up.

I expect that upon the reception of a CAN frame, It wakes up... But I see something else in practice

[igorpadykov]

this may depend on used hardware, apalis boards are developed and supported

by third party toradex and issue may be posted on community

https://www.toradex.com/community

Best regards
igor