Adding support for stm32 sdhc Zephyr driver

[ivanwagner]

Is there any plan on adding support for sdhc on the stm32 platform?

[ndrs-pst]

@ivanwagner l think it's already here
,🤔 https://github.com/zephyrproject-rtos/zephyr/blob/main/drivers%2Fdisk%2Fsdmmc_stm32.c

[ivanwagner]

I was thinking about his specifically: https://github.com/zephyrproject-rtos/zephyr/tree/main/drivers/sdhc

What's the difference?

[ndrs-pst]

That’s due to the difference between the MMC and SD specifications.

In short, here’s the wording from stm32h7xx_hal_mmc.c and stm32h7xx_hal_sd.c:

• SDMMC driver functions to interface with MMC and eMMC card devices.
• SDMMC driver functions to interface with SD and uSD card devices.

So, if you're using uSD card devices, then just leave the following CONFIG_SDMMC_STM32_EMMC

---

zephyr/drivers/disk/Kconfig.sdmmc

Lines 65 to 69 in ad0a1c7

	config SDMMC_STM32_EMMC
	bool "STM32 SDMMC eMMC mode"
	depends on SDMMC_STM32
	help
	Use eMMC instead of SDIO (SD card) protocol. These are similar, but not entirely the same.

[ivanwagner]

So to my understanding if the case would be a generic SDIO to communicate with a device, would SD be it?

[ndrs-pst]

In the context of using an SDIO interface with an external chip, such as a Wi-Fi chipset, I observed that Zephyr's codebase includes a driver for Infineon's AIROC Wi-Fi

zephyr/drivers/wifi/infineon/airoc_wifi.h

Lines 15 to 19 in ad3e941

	struct airoc_wifi_data {
	struct sd_card card;
	struct sdio_func sdio_func1;
	struct sdio_func sdio_func2;
	struct net_if *iface;

, which seems to be used in combination with, for example, this SDIO driver

zephyr/drivers/sdhc/ifx_cat1_sdio.c

Lines 306 to 315 in ad3e941

	static const struct sdhc_driver_api ifx_cat1_sdio_api = {
	.reset = ifx_cat1_sdio_reset,
	.request = ifx_cat1_sdio_request,
	.set_io = ifx_cat1_sdio_set_io,
	.get_card_present = ifx_cat1_sdio_get_card_present,
	.card_busy = ifx_cat1_sdio_card_busy,
	.get_host_props = ifx_cat1_sdio_get_host_props,
	.enable_interrupt = ifx_cat1_sdio_enable_interrupt,
	.disable_interrupt = ifx_cat1_sdio_disable_interrupt,
	};

This appears to be the closest match to what you are asking for.

In conclusion, aside from using an SD card, I'm afraid that STM32 is not yet supported.

FWIW, https://github.com/Infineon/AIROC-Wi-Fi-Bluetooth-STM32/blob/master/Middlewares/Third_Party/pal/targets/TARGET_STM32/Src/stm32_cyhal_sdio.c

[ivanwagner]

Hi @ndrs-pst thank you for your answer the situation is now clear to me.

[ndrs-pst]

It's my pleasure to help the community! I'm glad I could assist.

Through this investigation, I realized that the correct place for the STM32 SDMMC should be in
the SDHC subsystem and that it should implement the sdhc_driver_api instead of disk_operations.

Ping @erwango if you have any plan for this 👀

[erwango]

Yes, there are plans, but we're waiting a new HAL SDIO API which wouldn't include SDHC operations as it does today.
This should be completed before eoy.

[facchinm]

@erwango as you know we are mildly interested in the topic 😇 any updated estimation?