SDMMC internal peripheral

Applicable for

STM32MP13x lines, STM32MP15x lines

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1. Article purpose

The purpose of this article is to:

• briefly introduce the SDMMC peripheral and its main features,
• indicate the peripheral instances assignment at boot time and their assignment at runtime (including whether instances can be allocated to secure contexts),
• list the software frameworks and drivers managing the peripheral,
• explain how to configure the peripheral.

2. Peripheral overview

The SDMMC peripheral is used to interconnect STM32 MPU to SD memory cards, SDIO and MMC devices.

Refer to the STM32 MPU reference manuals for the complete list of features, and to the software frameworks and drivers, introduced below, to see which features are implemented.

3. Peripheral usage

This chapter is applicable in the scope of the OpenSTLinux BSP running on the Arm^® Cortex^®-A processor(s), and the STM32CubeMPU Package running on the Arm^® Cortex^®-M processor.

3.1. Boot time assignment

3.1.1. On STM32MP1 Series

SDMMC1/2 instances can be used to support memory boot on SD or MMC Flash devices.

The SDMMC3 (only present on STM32MP15x lines ) is not used at boot time.

Information

The SDMMC instances are ordered by address in the device tree arch/arm/boot/dts/stm32mp151.dtsi file for STM32MP15x lines : sdmmc3: sdmmc@48004000 { ... sdmmc1: sdmmc@58005000 { ... sdmmc2: sdmmc@58007000 { By default, in OpenSTLinux distribution, sdmmc3 is disabled so the sdmmc1 (SD card on Evaluation boards and Discovery kits) and sdmmc2 (eMMC on Evaluation boards and Wifi on Discovery kits) are respectively aliased to mmc0 and mmc1. If you enable sdmmc3, it will take the mmc0 alias and the aliases above will shift, so don't forget to update the Linux kernel boot command accordingly! For instance, 'root=/dev/mmcblk0p6' will become 'root=/dev/mmcblk1p6' to mount the rootfs from the sdmmc1 (SD card) when sdmmc3 is enabled.

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Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:

• ☐ means that the peripheral can be assigned (☑) to the given boot time context.
• ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
• ✓ is used for system peripherals that cannot be unchecked because they are statically connected in the device.

The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32 MPU reference manuals.

Domain	Peripheral	Boot time allocation				Comment
		Instance	Cortex-A7 secure (ROM code)	Cortex-A7 secure (TF-A BL2)	Cortex-A7 non-secure (U-Boot)
Mass storage	SDMMC	SDMMC1	✓	☐	☐
		SDMMC2	✓	☐	☐

3.2. Runtime assignment

3.2.1. On STM32MP13x lines 

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STM32MP13 internal peripherals

Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:

• ☐ means that the peripheral can be assigned (☑) to the given runtime context.
• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
• ✓ is used for system peripherals that cannot be unchecked because they are statically connected in the device.

Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP13 reference manuals.

Domain	Peripheral	Runtime allocation			Comment
		Instance	Cortex-A7 secure (OP-TEE)	Cortex-A7 non-secure (Linux)
Mass storage	SDMMC	SDMMC1	⬚	☐	Assignment (single choice)
		SDMMC2	⬚	☐	Assignment (single choice)

3.2.2. On STM32MP15x lines 

Expand

Click on the right to expand the legend...

STM32MP15 internal peripherals

Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:

• ☐ means that the peripheral can be assigned (☑) to the given runtime context.
• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
• ✓ is used for system peripherals that cannot be unchecked because they are statically connected in the device.

Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possiblities might be described in STM32MP15 reference manuals.

Domain	Peripheral	Runtime allocation				Comment
		Instance	Cortex-A7 secure (OP-TEE)	Cortex-A7 non-secure (Linux)	Cortex-M4 (STM32Cube)
Mass storage	SDMMC	SDMMC1		☐
		SDMMC2		☐
		SDMMC3		☐	☐	Assignment (single choice)

4. Software frameworks and drivers

Below are listed the software frameworks and drivers managing the SDMMC peripheral for the embedded software components listed in the above tables.

• Linux^®: Linux MMC framework
• STM32Cube: SDMMC HAL driver and header file of SD HAL module
• TF-A BL2: MMC framework (drivers/mmc/mmc.c ) and driver (drivers/st/mmc/stm32_sdmmc2.c )
• U-Boot: MMC framework (drivers/mmc/mmc.c ) and driver (drivers/mmc/stm32_sdmmc2.c )

5. How to assign and configure the peripheral

The peripheral assignment can be done via the STM32CubeMX graphical tool (and manually completed if needed).
This tool also helps to configure the peripheral:

• partial device trees (pin control and clock tree) generation for the OpenSTLinux software components,
• HAL initialization code generation for the STM32CubeMPU Package.

The configuration is applied by the firmware running in the context in which the peripheral is assigned.

For Linux^® kernel configuration, please refer to SDMMC device tree configuration.

Microprocessor unit

Secure digital

Secure digital input/output

Multimedia card

Board support package

Arm^® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

Cortex^®

Flash memory shortened to gain space in titles, tables and block diagrams

SD memory card (https://www.sdcard.org)

Former spelling for e•MMC ('e' in italic)

Linux^® is a registered trademark of Linus Torvalds.

Read only memory

Trusted firmware for Arm^® Cortex^®-A (see TF-A)

Boot loader stage 2

Das U-Boot -- the universal boot loader (see U-Boot)

Open portable trusted execution environment

Hardware abstraction layer

Microprocessor unit

Secure digital

Secure digital input/output

Multimedia card

Board support package

Arm^® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

Cortex^®

Flash memory shortened to gain space in titles, tables and block diagrams

SD memory card (https://www.sdcard.org)

Former spelling for e•MMC ('e' in italic)

Linux^® is a registered trademark of Linus Torvalds.

Read only memory

Trusted firmware for Arm^® Cortex^®-A (see TF-A)

Boot loader stage 2

Das U-Boot -- the universal boot loader (see U-Boot)

Open portable trusted execution environment

Hardware abstraction layer

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