AM62A3-Q1: How to enable main spi0 DMA mode on AM62Ax?

tao lu

Part Number: AM62A3-Q1
Other Parts Discussed in Thread: AM62A3, AM625

Tool/software:

Hi TI,

Refer to below page:

I see the need to add some configs in dts.

On my AM62A3 board, I have already enabled main_spi0, and it works fine. But the cpuload is very high(100%/400% for 4 cpu core).

So, I want to enable DMA mode of main_spi0 to check the cpuload can reduced or not.

Is it the same configs as AM625(k3-am625-sk.dts)?

+	dmas = <&main_pktdma 0xc300 0>, <&main_pktdma 0x4300 0>;
+	dma-names = "tx0", "rx0";

And, if enabled DMA, do this help reduce CPU load?

Thanks.

Tao

+1 Andreas Dannenberg 8 months ago

Hi Tao,

tao lu said:
Is it the same configs as AM625(k3-am625-sk.dts)?

To figure this out we need to compare and/or make sure the correct PSI-L Source and Destination Thread IDs are used for the SPI0 peripheral. For AM62A, those are documented in the TI SCI User's Guide here: https://software-dl.ti.com/tisci/esd/09_02_07/5_soc_doc/am62ax/psil_cfg.html#psi-l-source-and-destination-thread-ids

pdma_main0_mcspi0_rx

0x4300 to 0x4303

pdma_main0_mcspi0_tx

0xc300 to 0xc303

So yes, since the IDs are the same, the same device tree diff you have in your original post can also be used to enable DMA for SPI0 on AM62A.

tao lu said:
And, if enabled DMA, do this help reduce CPU load?

Yes. It will help reduce CPU load, and will also reduce the inter-byte gap.

Another thing you should consider is updating DMA_MIN_BYTES to your needs, to make sure the DMA is always used even for smaller transfers. You can find more info on that here: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1356551/faq-am6x-optimizing-spi-transfer-inter-byte-gaps-using-the-dma-in-linux

Regards, Andreas

0 tao lu 8 months ago in reply to Andreas Dannenberg

Hi Andreas,

I appreciate your questions and attention regarding the configuration of DMA_MIN_BYTES.

Thanks.

Tao

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