1. Purpose of article[edit source]
This article describes how to update the STM32 MPU embedded Software distribution to a specific 256MB DDR mapping in a STM32MP13x lines 
based product.
Note that the 256MB software configuration can be performed on a STM32MP135F-DK Discovery kit 
(512MB of DDR), in order to prototype the new mapping memory, but for this exercise, further software updates are requested, there are highlight in the article with a information window and the label DDR512MB.
2. Pre-requesites[edit source]
You are already familiar with the Yocto build process and OpenSTLinux distribution.
3. Introduction[edit source]
This article is a guideline for the user to update the STM32 MPU embedded Software in a distribution package of the OpenSTLinux distribution, according to his 256MB hardware configuration.
The process is based on a OpenSTLinux configured for the STM32MP135F-DK Discovery kit board (512MB of DDR), with the following DDR mapping.
The default mapping defined for The OpenSTLinux on the STM32MP135F-DK for a st-image-weston image is :
| 0xe0000000 | End of DDR 512MB |
| 0xde200000 | DDR_SEC_BASE/CFG_TZDRAM_START size DDR_SEC_SIZE/STM32MP_DDR_S_SIZE/CFG_TZDRAM_SIZE (30MB) protected |
| 0xde000000 | DDR_SHARE_BASE/CFG_SHMEM_START} size DDR_SHARE_SIZE/STM32MP_DDR_SHMEM_SIZE/CFG_SHMEM_SIZE (2MB no secure), |
| 0xdd000000 | Begin of optee-framebuffer protected access by TZC 400 size 16MB |
| 0xdc800000 | End of Linux CMA reserved |
| 0xd4800000 | Begin of Linux CMA reserved size CONFIG_CMA_SIZE_MBYTES 128MB |
| 0xd0000000 | End of DDR cacheable in U-Boot |
| 0xc0000000 | STM32MP_DDR_BASE DDR_NS_BASE size 464MB |
The exercise described in this article is to target the following 256MB mapping:
| 0xd0000000 | End of DDR 256MB |
| 0xcfc00000 | DDR_SEC_BASE/CFG_TZDRAM_START size DDR_SEC_SIZE/STM32MP_DDR_S_SIZE/CFG_TZDRAM_SIZE (4MB) protected by TZC 400, |
| 0xcfb00000 | DDR_SHARE_BASE/CFG_SHMEM_START size DDR_SHARE_SIZE/STM32MP_DDR_SHMEM_SIZE/CFG_SHMEM_SIZE (1MB no secure), |
| 0xceb00000 | Begin of optee-framebuffer protected access by TZC 400 size 16MB |
| 0xcb000000 | End of Linux CMA reserved |
| 0xc8000000 | End of DDR cacheable in U-Boot |
| 0xc3000000 | Begin of Linux CMA reserved size CONFIG_CMA_SIZE_MBYTES 128MB |
| 0xc0000000 | STM32MP_DDR_BASE DDR_NS_BASE size 235MB |
The software modification requested in the STM32MP1 Distribution Package, have been performed with the "devtool" and "bitbake" tools. The following components need to be modified (TF-A, U-Boot, OP-TEE, Linux Kernel).
4. DDR configuration[edit source]
The DDR is configured with the STM32CubeMX DDR tool, the tool creates the device tree source include file.
5. TF-A updates[edit source]
To update the TF-A firmware in the STM32MP1 Distribution Package, use the devtool tool:
devtool modify tf-a-stm32mp
The updates requested according to new mapping:
- Modify the DDR_SIZE (512MB->256MB) defined in file fdts/stm32mp135f-dk-fw-config.dts
#define DDR_SIZE 0x10000000
- Modify the DDR_SEC_SIZE (30 MB ->4MB) and DDR_SHARE_SIZE (2MB->1MB) defined in file fdts/stm32mp13-fw-config.dtsi
#define DDR_SEC_SIZE 0x400000 #define DDR_SHARE_SIZE 0x100000
- Modify the STM32MP_DDR_S_SIZE (30 MB ->4MB) and STM32MP_DDR_SHMEM_SIZE (2MB->1MB) defined in file plat/st/stm32mp1/stm32mp1_fip_def.h
#define STM32MP_DDR_S_SIZE 0x400000 #define STM32MP_DDR_SHMEM_SIZE 0x100000
5.1. Description of the TF-A updates[edit source]
For some further description please read the How to configure TF-A FW CONFIG.
- Firewall configuration
The DDR firewall is configured to restrict access to specific areas.The TZC is configured at boot time to setup DDR accesses by the TF-A, completed by OP-TEE.
Three regions are defined: Start address = 0xC000 0000: 251-Mbyte region where secure accesses are forbidden and to which all non- secure peripherals can access Start address = 0xCFB0 0000: 1-Mbyte (SHM) region where secure accesses are forbidden and non-secure accesses are possible only from an A7 CPU Start address = 0xCFC0 0000: 4-Mbyte (OP-TEE) region where only secure accesses are allowed
OP-TEE is the secure OS executed in DDR protected by TZC, the size allocated to OP-TEE depend on how the OP-TEE is configured and used, it includes the firmware Optee-os size, the stack and heap size, stack and heap are almost dedicated to Trusted Applications. SHM is the SHare Memory between non secure and secure OS (?? usage buffer for TA access ??;..)
The configuration of the mem firewall is defined in the file fdts/stm32mp13-fw-config.dtsi
DDR_NS_BASE = STM32MP_DDR_BASE = 0xc0000000 (default OpenSTLinux RAM mapping)) DDR_SEC_SIZE = 0x00400000 (4 MB allocated to OP-TEE). DDR_SEC_BASE = {{HighlightParam|STM32MP_DDR_BASE + DDR_SIZE - DDR_SEC_SIZE = 0xc0000000 + 0x10000000 - 0x00400000 = 0xcfc00000 DDR_SHARE_SIZE = 0x00100000 (1 MB allocated for Share memory) DDR_SHARE_BASE = DDR_SEC_BASE - DDR_SHARE_SIZE = 0xcfc00000 - 0x00100000 = 0xcfb00000 DDR_NS_SIZE = DDR_SHARE_BASE - DDR_NS_BASE = 0xcfb00000 - 0xc0000000 = 0x0fb00000 (251MB dedicated to no secure world, Linux kernel and user space)
- DDR Encryption area
The memory region encrypted is defined in fdts/stm32mp13-fw-config-mem-encrypt.dtsi . The memory region defined by default in OpenSTLinux configuration is the region allocated to OP-TEE, so set with parameters DDR_SEC_BASE and DDR_SEC_SIZE.
- Firmware configuration file
The FW_CONFIG define all binaries to be loading in internal RAM or DDR, with for each image the load address, the maximum binary size to be loaded, and the ID of the image. The FW_CONFIG and all binaries are embedded in a TF-A FIP binary. (Firmware Image Package). The TF-A FIP contains all boot binaries and optionally their certificates, installed by the TF-A. (U-Boot, U-Boot dtb, OP-TEE, FW_CONFIG)
The configuration is defined in the file fdts/stm32mp13-fw-config.dtsi The structure of the tos-fw (secure os) depend on the parameters DDR_SEC_BASE and DDR_SEC_SIZE.
6. OP-TEE updates[edit source]
To update the OP-TEE firmware in the STM32MP1 Distribution Package, use the devtool tool:
devtool modify optee-os-stm32mp
The updates requested according to new mapping:
- Modify the CFG_DRAM_SIZE (512MB->256MB), CFG_TZDRAM_SIZE (30MB->4MB) and CFG_SHMEM_SIZE (2MB->1MB) in the file Unsupported domain!.
CFG_DRAM_SIZE ?= 0x10000000 CFG_TZDRAM_SIZE ?= 0x00400000 CFG_SHMEM_SIZE ?= 0x00100000
- Modify the RAM memory size (512MB->256MB), the location of the secure framebuffer memory (0xdd000000->0xceb00000), in the file Unsupported domain!
memory@c0000000 {
device_type = "memory";
reg = <0xc0000000 0x10000000>;
};
reserved-memory {
#address-cells = <1>;
#size-cells = <1>;
ranges;
optee_framebuffer: optee-framebuffer@ceb00000 {
/* Secure framebuffer memory */
reg = <0xceb00000 0x1000000>;
st,protreg = <TZC_REGION_S_RDWR 0>;
};
6.1. Description of the updates[edit source]
- memory secure and share memory
The OP-TEE memory configuration is defined in the file Unsupported domain!
CFG_TZDRAM_START ?= ($(CFG_DRAM_BASE) + $(CFG_DRAM_SIZE) - $(CFG_TZDRAM_SIZE)) = 0xc0000000 + 0x10000000 - 0x400000 = 0xcfc00000 CFG_SHMEM_START ?= ($(CFG_TZDRAM_START) - $(CFG_SHMEM_SIZE)) = 0xcfc00000 - 0x100000 = 0xcfb00000
The memory size CFG_TZDRAM_SIZE and mapping reserved for OP-TEE depend on the task allocated to the secure OS.
The memory allocated include the size of the Optee-os firmware, the stack and heap size, almost of stack and heap are reserved to the Trusted Applications.
See the FAQ in OP-TEE documentation.[1]
- OP-TEE frame buffer
The OP-TEE frame buffer is a secure memory region dedicated to the display, used by Trusted UI in OP-TEE, protected by TZC. This region named optee-framebuffer is configured in OP-TEE device tree source Unsupported domain!.
7. U-Boot updates[edit source]
For some further description please read the U-Boot memory mapping.
To update the U-Boot firmware in the STM32MP1 Distribution Package, use the devtool tool:
devtool modify u-boot-stm32mp
The updates requested according to new mapping:
- Modify the RAM memory size (512MB->256MB), the location of the secure framebuffer memory (0xdd000000->0xceb00000), and the location (0xde000000->0xcfb00000) and size (30MB->5MB) of secure memory allocated to OP-TEE and SHM in the file arch/arm/dts/stm32mp135f-dk.dts
memory@c0000000 {
device_type = "memory";
reg = <0xc0000000 0x10000000>;
};
reserved-memory {
#address-cells = <1>;
#size-cells = <1>;
ranges;
optee_framebuffer@ceb00000 {
reg = <0xceb00000 0x1000000>;
no-map;
};
optee@cfb00000 {
reg = <0xcfb00000 0x00500000>;
no-map;
};
};
- Check the size of the DDR marked as-cacheable in U-Boot the in you defconfig file or for STM32MP135F-DK in configs/stm32mp15_defconfig , to avoid averlap with OP-TEE region:
CONFIG_DDR_CACHEABLE_SIZE 0x8000000
7.1. Description of the updates[edit source]
- Secure memory reserved
It is the memory reserved for secure OS OP-TEE and share memory and the OP-TEE framebuffer dedicated to the display, used by Trusted UI in OP-TEE. The size of the memory reserved for secure OS OP-TEE is calculated as the way CFG_TZDRAM_SIZE + CFG_SHMEM_SIZE = 5MB.
- Size of the DDR marked cacheable before relocation
CONFIG_DDR_CACHEABLE_SIZE define the size of the DDR marked as-cacheable before relocation in your U-Boot defconfig file to avoid overlap with secured regions.
This value need to be set at 128MB (0x8000000) because OP-TEE is located in the last 128MB of the 256MB DDR; it is done by default only after ecosystem release v4.1.0 for STMicroelectronics boards (configs/stm32mp13_defconfig and configs/stm32mp15_defconfig ) and 128MB is enough to executed the relocation; see U-Boot memory mapping for DDR usage before relocation.
In case of overlap between the cacheable area before U-Boot relocation and the reserved and secured by OP-TEE region, the U-Boot code execution on Arm® Cortex®-A7 normal world can generate a speculative access to this secured area which cause a firewall error.
8. Kernel Linux updates[edit source]
To update the Kernel Linux in the STM32MP1 Distribution Package, use the devtool tool :
$PC > devtool modify linux-stm32mp
The updates requested according to new mapping:
- Modify the RAM memory size (512MB->256MB), the location of the secure framebuffer memory (0xdd000000->0xceb00000), and the location (0xde000000->0xcfb00000) and size (30MB->5MB) of secure memory allocated to OP-TEE and SHM in the file arch/arm/dts/stm32mp135f-dk.dts
memory@c0000000 {
device_type = "memory";
reg = <0xc0000000 0x10000000>;
};
reserved-memory {
#address-cells = <1>;
#size-cells = <1>;
ranges;
optee_framebuffer@ceb00000 {
reg = <0xceb00000 0x1000000>;
no-map;
};
optee@cfb00000 {
reg = <0xcfb00000 0x00500000>;
no-map;
};
};
8.1. Description of the updates[edit source]
- secure memory reserved
see U-Boot updates description.
8.2. Linux kernel memory usage[edit source]
The resulting DDR Non Secure memory allocated to the Linux Kernel and userspace according to the mapping chosen for this exercise is: 0xceb00000 - 0xc0000000 = 0xeb00000 (235 MB).
Purpose of this paragraph is to highlight you about some components size you can modify to share the Non secure RAM according to your need, the Linux kernel, the RAM File system, the Contiguous Memory Area (CMA).
We can estimate minimal amount of required RAM at system startup of the kernel image, we talk here about the static RAM used par Kernel image and the RAM file system. The kernel image execute the command :
$PC > size vmlinux
Example of result with OpenSTLinux default image : 16,5MB
The initramfs/initrd is the temporary Root File system installed in RAM and used at the kernel init step, before mounting the final root file system.
The contain of the RAM FS can be adjust according to the new mapping, you need space for copy the .cpio compressed file and the space for the file system unpacked.
The default OpenSTLinux st-image-resize-initrd-openstlinux-weston-stm32mp13-disco.cpio.gz file is about 29.3MB. The decompressed File system size is 50.4 MB .
For this example the RAM FS has been decrease to about 30MB, the /boot/image has been deleted.
Contiguous Memory Area (CMA), The size is defined in the kernel configuration file CONFIG_CMA_SIZE_MBYTES. CONFIG_CMA_SIZE_MBYTES is set to 128 in the OpenSTLinux distribution package.
9. Traces/Debug[edit source]
To verify your 256MB config, some traces can be checked. The following traces have been obtained with a ST_OPTEE_DEBUG_LOG_LEVEL = "3" for the OP-TEE and a ST_TF_A_LOG_LEVEL_RELEASE = "40" for the TF-A.
Loading and boot of BL32 OP-TEE image.
INFO: Loading image id=4 at address 0xcfc00000 INFO: Image id=4 loaded: 0xcfc00000 - 0xcfc0001c INFO: OPTEE ep=0xcfc00000 INFO: OPTEE header info: INFO: magic=0x4554504f INFO: version=0x2 INFO: arch=0x0 INFO: flags=0x0 INFO: nb_images=0x1 INFO: BL2: Loading image id 21 INFO: Loading image id=21 at address 0xcfc00000 NOTICE: BL2: Booting BL32 INFO: Entry point address = 0xcfc00000
OP-TEE traces
TZC DDR access configuration by OP-TEE: D/TC:0 0 tzc_dump_state:473 region 0 D/TC:0 0 tzc_dump_state:476 region_base: 0x0000000000000000 D/TC:0 0 tzc_dump_state:479 region_top: 0x00000000ffffffff D/TC:0 0 tzc_dump_state:481 secure rw: TZC_REGION_S_NONE D/TC:0 0 tzc_dump_state:486 filter 0 enable Secure region (4MB) : OP-TEE D/TC:0 0 tzc_dump_state:473 region 1 D/TC:0 0 tzc_dump_state:476 region_base: 0x00000000cfc00000 D/TC:0 0 tzc_dump_state:479 region_top: 0x00000000cfffffff D/TC:0 0 tzc_dump_state:481 secure rw: TZC_REGION_S_RDWR D/TC:0 0 tzc_dump_state:486 filter 0 enable Non secure region(1MB) : Share memory D/TC:0 0 tzc_dump_state:473 region 2 D/TC:0 0 tzc_dump_state:476 region_base: 0x00000000cfb00000 D/TC:0 0 tzc_dump_state:479 region_top: 0x00000000cfbfffff D/TC:0 0 tzc_dump_state:481 secure rw: TZC_REGION_S_NONE D/TC:0 0 tzc_dump_state:486 filter 0 enable Secure region (16MB) : OP-TEE frame buffer D/TC:0 0 tzc_dump_state:473 region 3 D/TC:0 0 tzc_dump_state:476 region_base: 0x00000000ceb00000 D/TC:0 0 tzc_dump_state:479 region_top: 0x00000000cfafffff D/TC:0 0 tzc_dump_state:481 secure rw: TZC_REGION_S_RDWR D/TC:0 0 tzc_dump_state:486 filter 0 enable Non secure region (235 MB) : linux D/TC:0 0 tzc_dump_state:473 region 4 D/TC:0 0 tzc_dump_state:476 region_base: 0x00000000c0000000 D/TC:0 0 tzc_dump_state:479 region_top: 0x00000000ceafffff D/TC:0 0 tzc_dump_state:481 secure rw: TZC_REGION_S_NONE
U-Boot traces
U-Boot U-Boot 2021.10-stm32mp-r1 (Jan 27 2023 - 09:03:57 +0000) CPU: STM32MP135F Rev.Z Model: STMicroelectronics STM32MP135F-DK Discovery Board Board: stm32mp1 in trusted mode (st,stm32mp135f-dk) Board: MB1635 Var1.0 Rev.C-01 DRAM: 256 MiB
Select the boot mode 1: OpenSTLinux 2: stm32mp135f-dk-a7-examples Enter choice: 1: OpenSTLinux
Temporary file system and linux kernel compressed file loaded in RAM Retrieving file: /st-image-resize-initrd 21498257 bytes read in 909 ms (22.6 MiB/s) Retrieving file: /uImage 7701112 bytes read in 335 ms (21.9 MiB/s) append: root=PARTUUID=e91c4e10-16e6-4c0e-bd0e-77becf4a3582 rootwait rw console=ttySTM0,115200 Retrieving file: /stm32mp135f-dk.dtb 59732 bytes read in 16 ms (3.6 MiB/s)
Linux kernel boot traces
The memory trace show the kernel part (16MB) and the cma reserved (128MB) CONFIG_CMA_SIZE_MBYTE
[ 0.000000] Memory: 65704K/262144K available (12288K kernel code, 1242K rwdata, 3436K rodata, 1024K init, 186K bss, 65368K reserved, 131072K cma-reserved, 0K highmem)
10. References[edit source]
Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere. 