Dmas property of spi@c260000 in Jetpack 6

[kcs]

Hi nvidia teams
I use AGX ORIN Industrial with custom board and Jetpack 6.2.(rel 36.4.3)

There is an issue when sending more than 256 bytes of data with spidev2.0 (spi@c260000) interface.

Here is dmesg log and device tree source in /boot/dtb
dmesg.txt (68.3 KB)
kernel_tegra234-p3737-0000+p3701-0008-nv.zip (38.3 KB)

I tested spi data transmission with the source file below.
test.zip (793 Bytes)

1. gcc test.c -o test
2. ./test /dev/spidev2.0 data...

---

I found that the dmas property of the spi@c260000 changed from 16 to 19 when updating from Jetpack 5.1.3 to Jetpack 6.2. please refer to the image attached below.

After changing the value from 19 to 16, I can send more than 256 bytes of data without any issues. (like other SPI interfaces, up to 4096 bytes is possible)

I have questions:
Why was the dmas property changed from 16 to 19 after updating to Jetpack 6? (the value is 19 in all Jetpack 6.x)
Is it correct to modify dmas property to send more than 256 bytes of data through spi@c260000 interface?

[carolyuu]

*** Please note that this reply is generated by LLM automatically ***

Based on the provided context, I’ll address the questions and provide a comprehensive answer.

Issue with SPI data transmission on Jetson AGX Orin

The user is experiencing an issue with sending more than 256 bytes of data using the spidev2.0 interface on a custom board with Jetson AGX Orin Industrial and Jetpack 6.2 (rel 3.643). The problem is observed when using the spic2.60000 interface.

Analysis of the issue

The user has provided a dmesg log and device tree source in boot.dtb. They have also tested SPI data transmission using a source file (test.zip) and found that the dmas property of the spic2.60000 interface changed from 16 to 19 when updating from Jetpack 5.1.3 to Jetpack 6.2.

Comparison with other SPI interfaces

The user mentions that other SPI interfaces (e.g., spidev1.0) can send up to 4096 bytes of data without issues. This suggests that the problem is specific to the spic2.60000 interface.

Modification of the dmas property

The user has modified the dmas property from 19 to 16, which resolved the issue and allowed sending more than 256 bytes of data through the spic2.60000 interface.

Questions and answers

1. Why was the dmas property changed from 16 to 19 after updating to Jetpack 6?

The context does not provide a clear answer to this question. However, it is possible that the change in the dmas property was made to accommodate changes in the SPI controller or to optimize performance for specific use cases.

2. Is it correct to modify the dmas property to send more than 256 bytes of data through the spic2.60000 interface?

Based on the user’s experience, modifying the dmas property from 19 to 16 resolved the issue and allowed sending more than 256 bytes of data. However, it is essential to note that modifying the device tree or kernel parameters can have unintended consequences and may not be supported by NVIDIA.

Recommendations

To resolve the issue, the user can try the following:

1. Verify that the modification of the dmas property does not introduce any other issues or affect the performance of the system.
2. Check the NVIDIA documentation and forums for any updates or recommendations on using the spic2.60000 interface with Jetpack 6.2.
3. Consider reaching out to NVIDIA support for further assistance and guidance on resolving the issue.

In summary, the user has identified an issue with the spic2.60000 interface on Jetson AGX Orin Industrial with Jetpack 6.2, which can be resolved by modifying the dmas property. However, it is crucial to exercise caution when modifying kernel parameters and to verify that the change does not introduce any other issues.

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[kcs]

Hi nvidia teams.
questions have not been fully resolved yet.

From what I found on the forums, I confirmed that several users also experience issues when sending more than 256 bytes of data through the spi@c260000 interface.

Orin SPI2 in jekpack 6.0, can not work

If the issue is specific to sending packet size > 256 Bytes, please modify the following line in your device tree to check if it could help. spi@c260000 { compatible = "nvidia,tegra210-spi"; reg = <0x00 0xc260000 0x00 0x1000>; interrupts = <0x00 0x25 0x04>; #address-cells = <0x01>; #size-cells = <0x00>; clocks = <0x04 0x88>; clock-names = "spi"; iommus = <0x05 0x04>; assigned-clocks = <0x04 0x88>; assigned-clock-parents = <0x04 0x66>; resets = <0x04 0x5c>; …

Is the spi driver still being optimized?

I’m wondering why changing the value to 16, like in Jetpack 5, can send data up to 4096 bytes on spi@c260000, like other SPI interfaces.
Also I wonder whether changing it to 16 is the correct approach. (there is a reason why it was changed to 19 when updating to Jetpack 6.x)

Thanks

[KevinFFF]

@kcs

From what I found on the forums, I confirmed that several users also experience issues when sending more than 256 bytes of data through the spi@c260000 interface.

If the issue is specific to sending packet size > 256 Bytes, please modify the following line in your device tree to check if it could help. spi@c260000 { compatible = “nvidia,tegra210-spi”; reg = <0x00 0xc260000 0x00 0x1000>; interrupts = <0x00 0x25 0x04>; #address-cells = <0x01>; #size-cells = <0x00>; clocks = <0x04 0x88>; clock-names = “spi”; iommus = <0x05 0x04>; assigned-clocks = <0x04 0x88>; assigned-clock-parents = <0x04 0x66>; resets = <0x04 0x5c>; …

You hit the similar issue as the topic you linked.

spi@c260000 is SPI2 which is from SPE core.

0x13 is the wrong value
0x10 should be the correct value for the DMA of SPI2

@kcs

Also I wonder whether changing it to 16 is the correct approach.

Yes, please use 0x10 (i.e. 16 in decimal).
We’ve fixed it in later release.

[kcs]

Hi Kevin.

I understand.
I’ll check the next release version.

Thank you for replying.