S32G2 Linux LLCE debugfs interface

[m_bez]

I'm trying to set up LLCE filters to route some messages on can10 to can11, and route other messages to the host.

First, I would like to ask where the documentation for the debugfs interface is. There is an example in the S32G2_LinuxBSP_42.0_User_Manual.pdf, and modifying this allows the creation of filters between interfaces. However, I'm not sure how to create a filter that uses a mask or ID to send some traffic to the Linux host.

The file /sys/kernel/debug/llce_can_core/can_destinations/add/README refers to the LLCE Firmware User Guide. Where can I find this document, or perhaps some more examples of LLCE filter configurations?

[carlos_o · Accepted solution]

Apologies for the misunderstanding here are some comments to improve the script that you share and some explanations.

1.  "echo 0x7FF > /sys/kernel/debug/llce_can_core/can_filters/add/can_mask_id" means that only standard frames are received. The CAN ID of the standard frame is 11 bits, so the can_mask_id is 0x7FF, which means that only the lower 11 bits are concerned when the mask matches. If it is an extended frame ID (29-bit ID), change 0x7FF to 0x1FFFFFFF. If you want to ignore some bits, fill them with 0, for example, 0x7F0 means the last 4 bits are ignored.

2.  "echo mask > /sys/kernel/debug/llce_can_core/can_filters/add/entry" The mask here is not the incoming parameter mask_id, but the configuration filter mode is mask match or exact match, so you cannot mistakenly assign mask as an incoming parameter.

3.  "0xe > /sys/kernel/debug/llce_can_core/can_filters/add/tag" When configuring the basic filter, the tag value is strongly related to the channel. Here, 0xe corresponds to channel 14. You use channel 11, so it should be changed to "0xb > /sys/kernel/debug/llce_can_core/can_filters/add/tag"

[m_bez]

Hey Carlos, thanks for your reply. It took me some time to get back to you, because setting the tags correctly was the last big hurdle and I've made quite a bit of progress since. I've run into a new issue, but I'll open a new thread for that, since this one is getting quite long and contains too many topics already. Thanks for your help.

[m_bez]

Hey, @carlos_o 

Good news, we are making some progress. When I set up the tag to correspond to the interface number, the behavior changes.
The filter now _almost_ behaves as expected, I just get empty CAN frames when the mask matches. For clarity I've added a complete log with ###comments to explain the testing. 

1) At boot, the host receives data on both llcecan10 and llcecan11, regardless of canID

```

root@s32g274a-n4c0a53:~# candump any,0:0,#FFFFFFFF
llcecan11 1FFFFFFF [4] DE AD BE EF
llcecan10 00000000 [4] DE AD BE EF
```

2) Next, two filters are set up, to use 0x00000000 and 0x 1FFFFFFF as masks respectively.
```

11 enabled 0x00000000 0x00000000 0x000b 0x0010 524 4 mask short |

10 enabled 0x1fffffff 0x00000000 0x000a 0x0010 525 5 mask short |
```

3) the llcecan interfaces do report receiving _something_ when frames that match the masks are sent, but the contents are not received for some reason

```
root@s32g274a-n4c0a53:~# candump any,0:0,#FFFFFFFF
llcecan10 000 [0]
llcecan11 000 [0]
```

What could be the cause of these frames being displayed as empty? I've `cat`'ed anything that i thought might be relevant in the attached log.

To summarize, the filter now seems to be matching on the mask correctly, but the frames received by the host contain no data.

[carlos_o]

Hi @m_bez,

The llcecan10 and llcecan11 are initialized to not support the CANFD type, so the tags in the script need to be changed to 0x10a and 0x10b. If the channel supports CANFD type, the tag needs to be changed to 0xa and 0xb.

[carlos_o]

Hi @m_bez,

reviewing the script, you attached they are some values that I think you need to review, it is the can_dest, can_mask_id and msg_id. What are you objective to do with those values?

[m_bez]

Hey Carlos
> can_dest

This was taken from the provided example to create a filter that uses the host as destination. Usually this value refers to a destination created in `/sys/kernel/debug/llce_can_core/can_destinations/` , but in this case, no such destination exists. In the provided example, 0xFF was used when no destination existed, and I used the same.
> can_mask_id

This is the mask used to filter CAD emesages by ID, the default filters all used 0x00000000, so I used the same, to create a filter that passes all traffic to the host. I did also try using 0xFFFFFFFF, in case the mask works differently, but this dod not affect the behavior.
> msg_id

It is my understanding that this value is only used when creating an "exact" filter, and I expect this value to be ignored. I used 0x00000000, and did test to see it the filter behaves differently if ite receives a message with CAN identifier 0x00000000, but these messages are also not received by the host.

[carlos_o]

Hi @m_bez,

Your understanding of msg_id is correct.

can_mask_id as 0x00000000 is correct for the test you are doing to allow all id to pass.

How are you testing that the host is receiving or not the CAN msg?

[m_bez]

Hey @carlos_o

two ways. First, by monitoring the output of
`candump any,0:0,#FFFFFFFF`
Second, by monitoring the contents of
`/sys/class/net/llcecan11/statistics/`

With a can interface sending packets to llcecan11. I confirm that both methods of monitoring traffic indicate receiving traffic, and then I create the filter, and then it stops receiving traffic.

[carlos_o]

Hi @m_bez, 

thanks for sharing the details, I'm reviewing with the internal team the possibles root causes of this issue. We appreciate your patience. 

[carlos_o]

Hi @m_bez,

Let me review with the internal team what can be the root causes of this issue. This may take a longer response time. I'll come ASAP with further information. 

[carlos_o]

Hi @m_bez,

When you install the LLCE Driver + Firmware package, you can locate the LLCE Firmware User Guide at

C:\NXP\S32G_LLCE_1_0_9\firmware\llce_interface\doc

if you use the default install location. 

[m_bez]

Great, got it. Thanks! Will see if I can get the debugFS interface figured out from that.

[carlos_o]

Let me know if you have more questions.