STM32 SPI using DMA

[darexa]

I've been struggling with SPI for a few days and thought I'd ask here.
I have a display connected through 1-line SPI so I naturally need to send things quickly on that line.
So far I've not been using DMA and I've noticed that it is rather slow.
Looking at the signals I can see a ~2us gap between every byte sent and it seems to be overhead of some form in the LL driver.
Before trying to figure out if I can decrease that time I thought I'd try DMA instead but I can't get it to run properly.

I've enabled DMA:

CONFIG_SPI_STM32_DMA=y

I'm using SPI3 on a STM32L452, it is connected to DMA2, channel 1 and 2.
I've configured it like this:

&spi3 {
pinctrl-0 = <&spi3_sck_pc10_custom &spi3_mosi_pc12_custom>;
status = "okay";
cs-gpios = <&gpioa 15 GPIO_ACTIVE_LOW>;
dmas = <&dma2 2 3 0x20440>,
<&dma2 1 3 0x20480>;
dma-names = "tx", "rx";

..........
};

I've also enabled DMA2.

&dma2{
status = "okay";
};

What's happening is a timeout from "wait_dma_rx_tx_done" and I can confirm that the dma_callback is never called.
Anyone have any ideas what I'm doing wrong?

Edit: Changed the DMA config and now there's at least something happening even though it isnät working fully. Will report back.

[darexa]

So my first issue was incorrect dmas-setting. I had not set the request ID correctly to 3 that is correct according to the ref manual.
Second issue was that in the low level spi driver, chip select was pulled before SPI was enabled when using DMA. This is not the case when not using DMA. I'm fairly sure this is incorrect behaviour in the driver, but if anyone knows it is not please let me know otherwise I'll report an issue here.

[luuke]

Hey, would you mind showing your final DMA configuration?

[darexa]

Hey, would you mind showing your final DMA configuration?

I don't have access to the source code for my project anymore I´m afraid.
What I do remember though:

I created this issue: #43411
Looks like it has been fixed and merged since then but please confirm.
My edited first post may be what got it working along with the fix to the issue above.
Don't remember more than that, sorry.