dsi: add support for DSI host peripheral

[tegimeki]

Adapted from the stm32h7xx-hal implementation, changed to use register accessor functions and use the RCC enable/reset mechanisms which are different in the stm32f4xx-hal.

Changes the LtdcPins argument to the DisplayController to be an Option, as they aren't used (and aren't needed for DSI interfaces).

Tested on STM32F469I-DISC board, in this project (pending various crate updates before that BSP is directly usable)

[burrbull]

Changes the LtdcPins argument to the DisplayController to be an Option, as they aren't used (and aren't needed for DSI interfaces).

Not sure what is better. Option or additional constructor.

[tegimeki]

Changes the LtdcPins argument to the DisplayController to be an Option, as they aren't used (and aren't needed for DSI interfaces).

Not sure what is better. Option or additional constructor.

I wasn't sure either, so will follow any recommendations. Since the parameter isn't used it could be removed altogether; the purpose of the pin declarations appears to be for setting the ALT mode, which gets done by the calling code anyway. But if there are other intentions for this parameter we could make a separate constructor for the pin-less DSI case.

[burrbull]

LGTM. Do you have an example to add?

[tegimeki]

LGTM. Do you have an example to add?

I have an example in my BSP project but since that board requires SDRAM for framebuffer, it depends on stm32-rs/stm32-fmc#14 and #759 in order to work.

I could add an example which configures the DSI peripheral on the STM32F469I-DISCO board and puts it in pattern test mode, as this does not require SDRAM and I might even be able to pare-down or eliminate the LTDC in this case. I will try this out and if that would be interesting I can add it to this pull request.

[burrbull]

I could add an example which configures the DSI peripheral on the STM32F469I-DISCO board and puts it in pattern test mode, as this does not require SDRAM and I might even be able to pare-down or eliminate the LTDC in this case. I will try this out and if that would be interesting I can add it to this pull request.

Ok. Let's merge this PR and you open a new one with example when it will be ready.

[joelsa]

I have an example in my BSP project but since that board requires SDRAM for framebuffer, it depends on stm32-rs/stm32-fmc#14 and #759 in order to work.

I could add an example which configures the DSI peripheral on the STM32F469I-DISCO board and puts it in pattern test mode, as this does not require SDRAM and I might even be able to pare-down or eliminate the LTDC in this case. I will try this out and if that would be interesting I can add it to this pull request.

You can put an image in the internal flash, that way you also don't need the SDRAM.

It's what i did in this PR with an Example: embassy-rs/embassy#2976

[tegimeki]

You can put an image in the internal flash, that way you also don't need the SDRAM.

It's what i did in this PR with an Example: embassy-rs/embassy#2976

Good point and nice example @joelsa!

Though ultimately SDRAM is needed for rendering dynamically, I did make a simple HAL test which uses the built-in pattern generator in #789. Hopefully your stm32-fmc change will get in soon 😄