Enabling DMA on STM32H7

[pstadelmann]

Hi,

I have a project that uses a STM32H747 and output video using UVC in bulk mode. Since 0.18.0 enables support for DMA with dwc2, I tried it by simply adding :

#define CFG_TUD_DWC2_DMA_ENABLE 1

in my tusb_config.h file.

But now the computer doesn't even see the device as a camera, in fact lsusb does not list it with my custom descriptors.

Is there something else I need to do in order to use DMA ?

Thanks,

Patrick

[HiFiPhile]

But now the computer doesn't even see the device as a camera, in fact lsusb does not list it with my custom descriptors.
Is there something else I need to do in order to use DMA ?

What does it mean, USB no longer enumerate ?

[pstadelmann]

Yes I guess so.

With CFG_TUD_DWC2_DMA_ENABLE not defined, when I start my program that sets up TinyUSB, I see a new USB device (the list goes from 16 to 17), listed as "cafe:4020".

With #CFG_TUD_DWC2_DMA_ENABLE 1 I don't see the TinyUSB device.

I didn't do any investigation at first, thinking maybe I needed to do something else. I've now rerun both scenarios with #define CFG_TUSB_DEBUG 3. The logs are attached to this message.

Thanks!

tusb_log_wihtout_dma.txt
tusb_log_with_dma.txt

[HiFiPhile]

Please try to disabled DCache, cache clean/invalidate of STM32 hasn't been added yet. Although it's not hard referencing https://github.com/hathach/tinyusb/blob/master/src/portable/chipidea/ci_hs/ci_hs_imxrt.h

Also for H7 (not F7) USB packet buffer can't be placed in DTCM if DMA is enabled.

[pstadelmann]

I tried adding #define CFG_TUD_MEM_DCACHE_ENABLE 0 but without success.

Also for H7 (not F7) USB packet buffer can't be placed in DTCM if DMA is enabled.

I'm using a SMT32H747, but I'm not sure how to ensure that DTCM is not used not USB packets...

[HiFiPhile]

I tried adding #define CFG_TUD_MEM_DCACHE_ENABLE 0 but without success.

To disable DCache, you need to ensure SCB_EnableDCache() is not called by any Cube HAL initialization code.

It will have a performance impact until STM32 cache clean/invalidate is implemented.

I'm using a SMT32H747, but I'm not sure how to ensure that DTCM is not used not USB packets...

You need to define packet buffer section in

tinyusb/examples/device/cdc_uac2/src/tusb_config.h

Line 80 in 597446f

#ifndef CFG_TUSB_MEM_SECTION

Then ensure in linker script this section is placed in SRAM.

[HiFiPhile]

@Lurcy38 I'm going to add cache maintenance functions, now I've a NUCLEO-H7S3L8 to play with.

[Lurcy38]

hello HiFiPhile,

I tried to disable cache completly and enable the DMA , but the class video is not mounted on Windows
I have a device composite with HID + Video UAC on STM32N6, the HID works perfectly but not the video UAC
I can test pacthes if you want or more if you need ...

[HiFiPhile]

It could be a buffer alignment issue, try to change CFG_TUSB_MEM_ALIGN to 32.

PR is ON #2963

[Lurcy38]

Hello,

it is ok now, using an STM32 H7/N6

From the release TinyUSB 0.18.0

Add the following defines (probably some are useless):

#define CFG_TUD_DWC2_DMA_ENABLE 1
#define CFG_TUSB_MEM_ALIGN TU_ATTR_ALIGNED(4)
#define CFG_TUSB_MEM_SECTION attribute (( section(".usb_ram") ))

In the ICF IAR or linker script, in an uncached block add:
define block RW_NOCACHERAM with fixed order
{
section .usb_ram
};

Everything is OK, for CDC and UVC, perfect streaming H264 720@30.

Many thanks, HiFiPhile :)