How to configure flash memory for TF-A BL2

Applicable for

STM32MP13x lines, STM32MP15x lines

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1. Article purpose

This article explains how to configure the TF-A MTD frameworks:

• SPI NOR
• SPI NAND
• SPI MEM
• FMC NAND

These frameworks represent the memory-access organisation.

They use two different configurations:

• Device tree configuration
• Boot device configuration

If the peripheral is assigned to another execution context, refer to How to assign an internal peripheral to a runtime context article for guidelines on peripheral assignment and configuration.

2. Framework overview

2.1. Components description

• IO_Storage. The IO storage provides an abstraction layer to access storage devices.

• Boot device configuration. The Boot device configuration is a platform specific add-on to manage Flash memory settings.

• MTD core. The MTD core provides an abstraction layer for raw Flash memories.

• Raw NAND subsystem. The Raw NAND protocol is used in the MTD subsystem for interfacing NAND Flash memories.

• SPI-MEM subsystem. The SPI-MEM protocol is used in the MTD subsystem for interfacing all kinds of SPI memories (NORs, NANDs).

• SPI-NAND subsystem. The SPI-NAND protocol is used in the MTD subsystem for interfacing SPI NAND Flash memories.

• SPI-NOR subsystem. The SPI-NOR protocol is used in the MTD subsystem for interfacing SPI NOR Flash memories.

• FMC driver / FMC (Hardware) . Please refer to the FMC internal peripheral.

• QUADSPI driver / QUADSPI (Hardware). Please refer to the QUADSPI internal peripheral.

3. DT configuration

This hardware description is a combination of the STM32 microprocessor device tree files (.dtsi extension) and board device tree files (.dts extension). See the Device tree for an explanation of the device tree file split.

STM32CubeMX can be used to generate the board device tree. Refer to How to configure the DT using STM32CubeMX for more details.

4. Raw NAND Flash memory

4.1. Raw NAND DT configuration

For the DT bindings, refer to FMC_device_tree_configuration.

Warning

Only the device required to load images must be declared as a child node.

4.2. Raw NAND device configuration

Raw NAND access uses the raw NAND framework. Some additional parameters are required by the raw NAND framework to address the memory:

• the page size
• the block size
• the number of blocks per device
• the bus width (8 or 16 bits)
• the ECC algorithm (HW BCH8/BCH4/Hamming algorithms are available). The default ECC used is ECC NONE (no error correction).

Some memories are ONFI compliant. In that case, the required parameters can be directly read from the parameter description table.

For the others, the user must correctly fill-out the OTP fuses dedicated for NAND. For STM32MP15x lines  OTP9 should be filled, see STM32MP15 OTP mapping. For STM32MP13x lines  OTP9 and/or OTP10 should be filled, see STM32MP13 OTP mapping.

4.2.1. Raw NAND examples

• ONFI raw NAND with ECC override (default from parameter table is BCH4, force to BCH8).

OTP Word 9 : 0x18000

Use OTP	Page size		Block size		Block numbers (N * 256)								Width	ECC
0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

• 8-bit raw NAND (page size: 4 Kbytes, block size: 256 Kbytes, device size: 1024 Mbytes, ECC requirement: BCH4)

OTP Word 9 : 0xA0810000

Use OTP	Page size		Block size		Block numbers (N * 256)								Width	ECC
1	0	1	0	0	0	0	0	1	0	0	0	0	0	0	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

• 16-bit raw NAND (page size: 8 Kbytes, block size: 512 Kbytes, device size: 2048 Mbytes, ECC requirement: ON-DIE)

OTP Word 9 : 0xc0860000

Use OTP	Page size		Block size		Block numbers (N * 256)								Width	ECC
1	1	0	0	0	0	0	0	1	0	0	0	0	1	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

5. SPI NAND flash memory

5.1. SPI NAND DT configuration

For the DT bindings, refers to the QUADSPI_device_tree_configuration.

Warning

Only the device required to load images must be declared as a child node

5.2. SPI NAND device configuration

SPI NAND and SPI MEM frameworks are used to address such memories.

5.2.1. SPI NAND framework

SPI NAND framework requires additional parameters:

• the page size
• the block size
• the number of blocks per device
• the number of planes per device.

These parameters must be correctly filled out by the user in OTP fuses. For STM32MP15x lines  OTP9 should be filled, see STM32MP15 OTP mapping. For STM32MP13x lines  OTP9 and/or OTP10 should be filled, see STM32MP13 OTP mapping.

By default, the READ FROM CACHE x1 command is used (opcode: 0x03). It is possible to override this command in the platform configuration to improve memory-access performance .

5.2.2. SPI NAND example

• SPI NAND (page size: 2 Kbytes, block size: 128 Kbytes, device size: 256 Mbytes, 2 planes)

OTP Word 9 : 0x80404000

Use OTP	Page size		Block size		Block numbers (N * 256)								Not Used	Not Used			2 Planes
1	0	0	0	0	0	0	0	0	1	0	0	0	0	0	0	0	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0

• Update the READ FROM CACHE x1 command to use the READ FROM CACHE x4 command (opcode: 0x6B) defined in platform file

device->spi_read_cache_op.cmd.opcode = SPI_NAND_OP_READ_FROM_CACHE_4X;
device->spi_read_cache_op.cmd.buswidth = SPI_MEM_BUSWIDTH_1_LINE;
device->spi_read_cache_op.addr.nbytes = 2U;
device->spi_read_cache_op.addr.buswidth = SPI_MEM_BUSWIDTH_1_LINE;
device->spi_read_cache_op.dummy.nbytes = 1U;
device->spi_read_cache_op.dummy.buswidth = SPI_MEM_BUSWIDTH_1_LINE;
device->spi_read_cache_op.data.buswidth = SPI_MEM_BUSWIDTH_4_LINE;
device->spi_read_cache_op.data.dir = SPI_MEM_DATA_IN;

6. MTD Framework - NAND specific

6.1. NAND error management

The TF-A BL2 MTD framework implements a retry mechanism link to NAND specification. It allows to skip some bad blocks when loading binaries or switching to a backup partition if uncorrectable error is detected. A PLATFORM_MTD_MAX_PART_SIZE defines the partition size to find a binary and its backups in the plat/st/stm32mp1/stm32mp1_def.h . It can be increased or decreased depending the binary size (i.e FIP size and its backups).

On some specific NAND devices with ON-DIE ECC, an uncorrectable error is not checked and may result on a incomplete binary loaded with a boot failure.

Information

It is strongly recommended to use the Trusted Board Boot when using NAND memories to control the binary integrity loaded and avoid issues.

6.2. Firmware Update

In case of Firmware update feature enabled, specific FIP offset for A (STM32MP_NAND_FIP_A_OFFSET) and B partition (STM32MP_NAND_FIP_B_OFFSET) are fixed in the plat/st/stm32mp1/stm32mp1_fip_def.h . They must be adapted depending on the FIP size loaded. They must be aligned with the PLATFORM_MTD_MAX_PART_SIZE previously explained.

7. SPI NOR Flash memory

7.1. SPI NOR DT configuration

For the DT bindings, refer to the QUADSPI_device_tree_configuration.

Warning

Only the device required to load images must be declared as a child node.

7.2. SPI NOR device configuration

SPI NOR and SPI MEM frameworks are used to address such memories.

7.2.1. SPI NOR framework

SPI NOR framework requires additional parameter:

• Device size

This parameter needs to be defined in the platform configuration file.

By default, the READ command is used (opcode: 0x03). It is possible to override this command in the platform configuration to improve memory-access performance .

7.2.2. SPI NOR example

• SPI NOR (device size: 64 Mbytes)

	device->size = SZ_64M;                                --> Device size

• Update the READ command to use QREAD command (opcode: 0x6B) defined in platform file

	device->read_op.cmd.opcode = SPI_NOR_OP_READ_1_1_4;
	device->read_op.cmd.buswidth = SPI_MEM_BUSWIDTH_1_LINE;
	device->read_op.addr.nbytes = 3U;
	device->read_op.addr.buswidth = SPI_MEM_BUSWIDTH_1_LINE;
	device->read_op.dummy.nbytes = 1U;
	device->read_op.dummy.buswidth = SPI_MEM_BUSWIDTH_1_LINE;
	device->read_op.data.buswidth = SPI_MEM_BUSWIDTH_4_LINE;
	device->read_op.data.dir = SPI_MEM_DATA_IN;

8. How to configure the DT using STM32CubeMX

The STM32CubeMX tool can be used to configure the STM32MPU device and get the corresponding platform configuration device tree files.
The STM32CubeMX might not support all the properties described in your device DT bindings (see the above Raw NAND, SPI NAND or SPI NOR dedicated DT configuration paragraphs). If so, the tool inserts user sections in the generated device tree. These sections can then be edited to add some properties, and they are preserved from one generation to another. Refer to the STM32CubeMX user manual for further information.

9. References

Please refer to the following links for additional information:

Trusted firmware for Arm^® Cortex^®-A

Memory technology device

Serial peripheral interface

input/output

Flash memories combine high density and cost effectiveness of EPROMs with the electrical erasability of EEPROMs. For this reason, the Flash memory market is one of the most exciting areas of the semiconductor industry today and new applications requiring in system reprogramming, such as cellular telephones, automotive engine management systems, hard disk drives, PC BIOS software for Plug & Play, digital TV, set top boxes, fax and other modems, PC cards and multimedia CD-ROMs, offer the prospect of very high volume demand.

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

Device tree

Elliptic curve cryptography

Error correction capability

Open NAND flash interface (The ONFI working group, acronym for Open NAND flash interface, was founded in 2005. The group’s mission consists in creating a common industry standard for NAND Flash interfaces, to simplify integration of NAND Flash memory into consumer electronics (CE) devices and computing platforms. ST is one of the co-founder companies together with Hynix, Intel, Micron, Phison and Sony.)

One time programmed

Firmware image package is a packaging format used by TF-A

Trusted firmware for Arm^® Cortex^®-A

Memory technology device

Serial peripheral interface

input/output

Flash memories combine high density and cost effectiveness of EPROMs with the electrical erasability of EEPROMs. For this reason, the Flash memory market is one of the most exciting areas of the semiconductor industry today and new applications requiring in system reprogramming, such as cellular telephones, automotive engine management systems, hard disk drives, PC BIOS software for Plug & Play, digital TV, set top boxes, fax and other modems, PC cards and multimedia CD-ROMs, offer the prospect of very high volume demand.

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

Device tree

Elliptic curve cryptography

Error correction capability

Open NAND flash interface (The ONFI working group, acronym for Open NAND flash interface, was founded in 2005. The group’s mission consists in creating a common industry standard for NAND Flash interfaces, to simplify integration of NAND Flash memory into consumer electronics (CE) devices and computing platforms. ST is one of the co-founder companies together with Hynix, Intel, Micron, Phison and Sony.)

One time programmed

Firmware image package is a packaging format used by TF-A

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

Cortex^®