DDRPERFM internal peripheral

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1. Article purpose[edit source]

The purpose of this article is to:

briefly introduce the DDRPERFM peripheral and its main features
indicate the level of security supported by this hardware block
explain how it can be allocated to the three runtime contexts and linked to the corresponding software components
explain, when necessary, how to configure the DDRPERFM peripheral.

2. Peripheral overview[edit source]

The DDRPERFM peripheral is used to count various DDRCTRL events, for performance analysis.

2.1. Features[edit source]

The read, write and time counters are certainly the ones that are the most useful from user point of view, since they allow computing the DDR read and write throughputs.

Other counters are available in order to monitor the DDR controller arbitration dynamic, refresh commands and low-power management.

Refer to the STM32MP15 reference manuals for the complete list of features, and to the software components, introduced below, to see which features are implemented.

2.2. Security support[edit source]

The DDRPERFM is a non-secure peripheral.

3. Peripheral usage and associated software[edit source]

3.1. Boot time[edit source]

The DDRPERFM is not used at boot time.

3.2. Runtime[edit source]

3.2.1. Overview[edit source]

The DDRPERFM is allocated to the Arm^® Cortex^®-A7 non-secure core to be controlled in Linux^® by the perf framework.

Chapter Peripheral assignment describes which peripheral instance can be assigned to which context.

3.2.2. Software frameworks[edit source]

Domain	Peripheral	Software components			Comment
Domain	Peripheral	OP-TEE	Linux	STM32Cube	Comment
Trace & Debug	DDRPERFM		Linux perf^[1] framework

3.2.3. Peripheral configuration[edit source]

The configuration is applied by the firmware running in the context to which the peripheral is assigned. The configuration can be done alone via the STM32CubeMX tool for all internal peripherals, and then manually completed (particularly for external peripherals), according to the information given in the corresponding software framework article.

3.2.4. Peripheral assignment[edit source]

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.
✓ 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 a runtime 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
Domain	Peripheral	Instance	Cortex-A7 secure (OP-TEE)	Cortex-A7 non-secure (Linux)	Cortex-M4 (STM32Cube)	Comment
Trace & Debug	DDRPERFM	DDRPERFM		✓

4. How to go further[edit source]

Refer to How to measure the DDR throughput to learn how to use the DDRPERFM internal peripheral via the perf tool.

5. References[edit source]

↑ drivers/perf/stm32_ddr_pmu.c

[1] rivers/perf/stm32_ddr_pmu.c

[1]