How to Enable DMA for USB for IMX8M Plus based on Linux kernel 6.6.54

[radhak4x]

Hi 

I am trying to enable DMA for USB based on linux kernel 6.6.54. what are the required changes that are needed as part of dtb's along with driver changes? 

also what is the maximum hardware buffer that is used in transfer by default for 2.0 and 3.0

appreciate your support here 

i am referring to ehci-hcd.c - drivers/usb/host/ehci-hcd.c - Linux source code v6.6.54 - Bootlin Elixir Cross Referenc... source code

DTB changes as per my understanding:

&usb1 {
status = "okay";
dr_mode = "host";
dma-coherent;
#address-cells = <1>;
#size-cells = <0>;
};

is this correct ? what are the driver changes needed  to enable DMA for USB 

[JosephAtNXP]

Hi,

Thank you for your interest in NXP Semiconductor products,

It has an embedded DMA controller in each core. DMA doesn't need to be enabled and you can reference your nodes in EVK nodes.

For TX, the USB DMA source is system memory and the destination is the USB module internal FIFO. For RX, the source is the USB controller FIFO and destination is system memory.

The DMA is used to transfer the data between Tx/RxBuffer and the controller in summary and there you can also find the DMA range.

Doc for DWC3.

Regards

[radhak4x]

Hi Joseph,

Could you please elaborate what is meant by EVK nodes?

In reference manual, could you please point - where that USB already has Embedded DMA in it.

as we don't see / not found that part in IMX8 Ref Manual?

[radhak4x]

Hi joseph,

Could you please elaborate the same ?

thanks
Radha

[JosephAtNXP]

Hi @radhak4x,

I'm still researching this issue, I will clarify it, thank you for your patience.

Regards,

[radhak4x]

What is the maximum hardware buffer defined for this ? i have referred to Reference manual - i.MX 8M Plus Applications Processor Reference Manual chapter 11 and i hardly found this data.