SK-TDA4VM: How to interface m_can_platform kernel module with userspace application ?

Alark Mishra

Part Number: SK-TDA4VM

Hello,

My requirement is to stream bytes over the CAN interface (can0, can5 and can9) without the CAN protocol (Application layer).

I am assuming m_can_platform kernel driver can let me do that as socket CAN is unable to stream bytes.

Can anybody please let me know how can I interact with m_can_platform kernel driver once it is inserted as I am unable to find ioctl calls attached with it and also there are no open, write, read calls there.

Task will be as follows:

Insert m_can and m_can_platform driver
Run the userspace application that interacts with above kernel modules.
Stream bytes as and when required.

Cordially,
Alark Mishra

over 2 years ago

0 Tarun Mukesh Puvvada over 2 years ago

TI__Guru 59306 points

Hi,

Assigning this to expert.

Regards

Tarun Mukesh

0 Takuma Fujiwara over 2 years ago in reply to Tarun Mukesh Puvvada

TI__Guru 58693 points

Hi Alark,

Was this FAQ followed? https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1132406/faq-sk-tda4vm-how-do-i-use-the-can-bus-headers-on-sk-tda4vm-using-edge-ai-sdk

If you have followed this and are not seeing any output, then it could be related to this issue that will be fixed in our upcoming SDK release: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1316957/sk-tda4vm-does-sk-tda4vm-board-support-can-communication-on-linux-a72-if-so-how-to-enable-it. Workaround would be to use an older release, or define the CAN interface in device tree, assuming this is causing you issues where you are not able to interact with the CAN driver.

Regards,

Takuma

0 Alark Mishra over 2 years ago in reply to Takuma Fujiwara

Prodigy 90 points

Hi Takuma,

No its not about using can0, can5 and can9 interface. I want to use mcan and for that TI has provided with m_can and m_can_platform drivers, how a userspace application can communicate with these kernel modules I want to know.

If you remember on another thread I was talking about streaming bytes over can interface, it can be done using m_can I believe, for this purpose I am asking how can I use these kernel modules (m_can and m_can_platform) ?

Cordially,
Alark Mishra

0 Takuma Fujiwara over 2 years ago in reply to Alark Mishra

TI__Guru 58693 points

Hi Alark,

Alark Mishra said:
I want to use mcan and for that TI has provided with m_can and m_can_platform drivers, how a userspace application can communicate with these kernel modules I want to know.

For this purpose, I would recommend the FAQ in my previous post. The kernel module is bound to the MCAN interface as shown in the "compatible" field in the device tree: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti/k3-j721e-main.dtsi?h=ti-linux-5.10.y#n2414. The compatible field translates to this line in the kernel driver: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/drivers/net/can/m_can/m_can_platform.c?h=ti-linux-6.1.y#n226. So, using the CAN interface on SK-TDA4VM should use the kernel driver underneath.

If the FAQ is followed there are instructions to run the userspace application, cansend and candump, for sending and receiving CAN messages. I assumed this was what was being asked for, but let me know if that was not the purpose of your question and please help clear up my misunderstandings.

Regards,

Takumja

0 Alark Mishra over 2 years ago in reply to Takuma Fujiwara

Prodigy 90 points

Hello Takumja,

Thanks for the information but yeah I understand the compatible field and that is clear to me.

See when we run candump and cansend it do not insert the m_can and m_can_platform kernel modules, neither these modules are automatically installed in the kernel on booting up.

And also candump and cansend userspace application utilize can and can_raw kernel modules. I request you to correct if I am wrong anywhere but I have got this observation after playing with all the provided kernel modules in TI Build.

That is why I have this question that when cansend, candump and socket CAN APIs do not use m_can and m_can_platform kernel modules, then how a userspace application can use these ?

Whole purpose is to stream bytes without CAN protocol on CAN interface and for this I am wishing to use m_can and m_can_platform kernel modules because rest all the methods imply CAN protocol rules to transfer bytes over CAN interface, for example:

cansend and candump uses socket CAN to transfer/read bytes over can0, can5 and can9 interface,
socketCAN APIs are there which when used in our source code will facilitate CAN protocol in our application,
But what to do when m_can and m_can_platform kernel modules are inserted in kernel, how my C code can talk to these drivers ?

I hope my explanation makes my requirement clear ?

Cordially,
Alark Mishra

+1 Takuma Fujiwara over 2 years ago in reply to Alark Mishra

TI__Guru 58693 points

Hi Alark,

I am not quite sure if I understand the question still... but here are some experiments I have tried, which you can also reproduce:

Does "lsmod | grep -i can" show m_can and m_can_platform?
Does "dmesg | grep -i can" show that m_can device is registered?
If you do something like this patch, do you see the kernel print things out? Note: this messes up some timing so most likely CAN interface may not be able to actually send/receive, but it should print some debug messages out when you send with cansendhttps://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/791/0001_2D00_DEBUG_2D00_ONLY_2D00_add_2D00_printk_2D00_statements_2D00_to_2D00_m_5F00_can_5F00_platform.patch
For example, I get the following logs from m_can_platform driver:
```
root@tda4vm-sk:/opt/edgeai-gst-apps# cansend can1 123#1122334455667788
[  152.459988] debug: reading reg
[  152.998237] debug: reading reg
[  153.001296] debug: reading reg
[  153.004338] debug: writing fifo
[  153.007390] debug: writing fifo
[  153.010524] debug: writing fifo
[  153.013664] debug: writing fifo
[  153.016805] debug: writing reg
root@tda4vm-sk:/opt/edgeai-gst-apps# 
```

From above experiments, it looks like m_can_platform driver is probed at boot and are in use at runtime when using the can-utils tools like cansend, or at least, they are used in the lower levels of the driver.

Regards,

Takuma

0 Alark Mishra over 2 years ago in reply to Takuma Fujiwara

Prodigy 90 points

Ok Takuma,

I think I understood your point, you are saying that m_can and m_can_platform are being used by cansend and candump userspace applications.

I'll reconfirm this thing and then can let you know.

I'll reply once I have tried few things, please expect a bit of delay.

Cordially,
Alark Mishra

0 Takuma Fujiwara over 2 years ago in reply to Alark Mishra

TI__Guru 58693 points

Hi Alark,

Ok, understood. Please keep us informed at your convenience.

Regards,

Takuma

+1 Alark Mishra over 2 years ago in reply to Takuma Fujiwara

Prodigy 90 points

Hi Takuma,

I have made use of TJA1050 CAN controller module for my purpose. That is also a voltage level shifter between UART and CAN so that should solve my requirement.

Changing kernel module will not help me as I have to use Standard CAN Interface as well alongside UART to CAN level shifter.

Thanks for your support !

Cordially,
Alark Mishra

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SK-TDA4VM: How to interface m_can_platform kernel module with userspace application ?