DDRCTRL and DDRPHYC internal peripherals

Applicable for

STM32MP13x lines, STM32MP15x lines

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1. Article purpose

The purpose of this article is to:

• briefly introduce the DDRCTRL and DDRPHYC peripherals and their 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 peripherals,
• explain how to configure the peripherals.

2. Peripheral overview

The DDRCTRL and DDRPHYC peripherals are used to configure the physical interface to the external DDR memory. Access to the DDR memory can be filtered via the TZC controller.

Notice that it is possible to perform DDR bandwidth measurement thanks to the DDRPERFM internal peripheral.

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

The DDRCTRL and DDRPHYC peripherals are kept secure and used by the FSBL to initialize the access to the DDR where it loads the SSBL (U-Boot) for execution.
STMicroelectronics wishes to make the DDR memory configuration as easy as possible, for this reason a dedicated application note has been published and a DDR tuning function is available in STM32CubeMX tool in order to generate the device tree configuration that is given to the FSBL to perform this initialization.

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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 is assigned by default to the given boot time context and that the peripheral is mandatory for the STM32 MPU Embedded Software distribution.
• ⬚ 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 hardware 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)
Core/RAM	DDR via DDRCTRL	DDR		☑	⬚

3.2. Runtime assignment

The DDRCTRL and DDRPHYC peripherals are accessed at runtime by the secure monitor (from the FSBL or OP-TEE) to put the DDR in self-refresh state before going into Stop or Standby low power mode:

• On STM32MP13x lines , OP-TEE is default located in DDR and it jumps into TF-A BL2 FSBL resident code in SYSRAM to configure the DDRCTRL and DDRPHYC
• On STM32MP15x lines , OP-TEE is default located in SYSRAM so it embeds the services to configure the DDRCTRL and DDRPHYC

On Standby exit, the ROM code loads the FSBL that again configures the DDRCTRL and DDRPHYC before proceeding with the wake-up procedure.

The TZC controller configures DDR memory access.

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 is assigned by default to the given runtime context and that the peripheral is mandatory for the STM32 MPU Embedded Software distribution.
• ⬚ 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 hardware 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)
Core/RAM	DDR via DDRCTRL	DDR	☑	⬚

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 is assigned by default to the given runtime context and that the peripheral is mandatory for the STM32 MPU Embedded Software distribution.
• ⬚ 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 hardware 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)
Core/RAM	DDR via DDRCTRL	DDR	☑	⬚

4. Software frameworks and drivers

Below are listed the software frameworks and drivers managing the DDRCTRL and DDRPHYC peripherals for the embedded software components listed in the above tables.

• OP-TEE: DDR OP-TEE driver (On STM32MP15x lines )
• TF-A BL2: TF-A BL2 DDR resident driver in SYSRAM (On STM32MP13x lines )

5. How to assign and configure the peripheral

The DDRCTRL and DDRPHYC device tree configuration is generated via STM32CubeMX tool, according to the DDR characteristics (type, size, frequency, speed grade). This configuration is applied during boot time by the FSBL (see boot chain overview).

Doubledata rate (memory domain)

Board support package

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

Cortex^®

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)

Random access memory (Early computer memories generally hadserial access. Memories where any given address can be accessed when desired were then called "random access" to distinguish them from the memories where contents can only be accessed in a fixed order. The term is used today for volatile random-acces ssemiconductor memories.)

First stage boot loader

Open portable trusted execution environment

Linux^® is a registered trademark of Linus Torvalds.

Doubledata rate (memory domain)

Board support package

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

Cortex^®

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)

Random access memory (Early computer memories generally hadserial access. Memories where any given address can be accessed when desired were then called "random access" to distinguish them from the memories where contents can only be accessed in a fixed order. The term is used today for volatile random-acces ssemiconductor memories.)

First stage boot loader

Open portable trusted execution environment

Linux^® is a registered trademark of Linus Torvalds.