[miyazakh]

Adds wolfBoot support for the NXP i.MX 8M Mini, tested on the TechNexion PICO-IMX8MM (PICO-PI baseboard).

Boot modes

• BL33 (default, IMX8MM_BL33=1): wolfBoot replaces U-Boot proper.
  BootROM -> U-Boot SPL -> ATF (BL31) -> wolfBoot -> Linux.
  wolfBoot reads a signed FIT (kernel + DTB) from eMMC p1 (FAT32, /fitImage_A.itb / /fitImage_B.itb), verifies it and boots Linux at EL2.
• RAM-boot (IMX8MM_BL33=0): started from U-Boot proper with go 0x40480000; the signed kernel is bundled after wolfBoot.

Changes

• src/sdhci.c: optional eMMC bus width and High Speed timing (SDHCI_EMMC_BUS_WIDTH, SDHCI_EMMC_HS). Defaults unchanged for other targets.
• hal/imx8mm.*: UART2 console, uSDHC3 eMMC through the SDHCI layer (register shim from hal/imx8qm.c), identity MMU + D-cache with SDMA cache maintenance in BL33 mode.
• config/examples/imx8mm-pico.config, test-app/app_imx8mm.c, Makefile (MAIN_TARGET), 3 CI build jobs.
• tools/scripts/imx8mm/: build flash.bin (BL33), the signed FIT, and the go image.
• docs/Targets.md: "NXP i.MX 8M Mini" section.

Testing

• Built with Ubuntu GCC 13.3 and Linaro GCC 6.4.1 (all CI variants).
• On hardware: eMMC standalone boot, A/B slot selection, signature verification and Linux boot (6.1.55 and 6.12.49 with the TechNexion Yocto rootfs). Load + verify of a 27 MB FIT takes about 1.7 s.
• Boot chain set up from a fresh clone with u-boot-tn-imx tn-imx_v2023.04_6.1.55_2.2.0-stable and its install_uboot_imx8.sh.

Notes

• HABv4 (authentication of wolfBoot itself) is not set up yet.
• DTBs from the Linux tree lack /memory and bootargs (U-Boot normally adds them); imx8mm-mkfit.sh adds them before signing.

[Copilot]

🟡 Changes recommended

The image-generation scripts can reject valid bootargs or produce images that overlap memory or exceed runtime limits.

3 open findings

• Validate ELF _end to prevent signed kernel overwrite · New
• Append root argument when DTB bootargs lacks root · New
• Enforce 42 MiB kernel size limit · New

What changed in this PR

Adds NXP i.MX 8M Mini support for BL33 and U-Boot go boot flows.

Changes:

• Adds i.MX8MM HAL, linker layout, configuration, test payload, and CI builds.
• Extends SDHCI with configurable eMMC width and High Speed timing.
• Adds scripts and documentation for producing signed FIT, go, and flash images.

File	Description
.github/​workflows/​test-configs.yml	Adds three i.MX8MM build variants.
.gitignore	Ignores generated i.MX8MM artifacts.
Makefile	Defines i.MX8MM build outputs.
config/​examples/​imx8mm-pico.config	Configures PICO-IMX8MM boot modes.
docs/​Targets.md	Documents setup, booting, and limitations.
hal/​imx8mm.c	Implements UART, MMU/cache, and uSDHC HAL support.
hal/​imx8mm.h	Defines i.MX8MM hardware constants.
hal/​imx8mm.ld	Defines the DRAM memory layout.
include/​sdhci.h	Adds eMMC High Speed constants.
src/​boot_aarch64.c	Includes the i.MX8MM platform header.
src/​boot_aarch64_start.S	Adds i.MX8MM EL2 startup handling.
src/​sdhci.c	Adds configurable eMMC width and timing.
test-app/​app_imx8mm.c	Adds a bare-metal boot payload.
tools/​scripts/​imx8mm/​imx8mm-mkfit.sh	Builds signed kernel/DTB FIT images.
tools/​scripts/​imx8mm/​imx8mm-mkflashbin.sh	Builds BL33 flash images.
tools/​scripts/​imx8mm/​imx8mm-mkgoimage.sh	Builds U-Boot go images.

🧠 Review effort: Balanced

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[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #931

Scan targets checked: wolfboot-src, wolfboot-bugs
Coverage: 2 of 5 in-scope changed file(s) opened by the reviewer; not opened: include/sdhci.h, src/boot_aarch64.c, test-app/app_imx8mm.c

Fenrir result: Approved ✅

No new issues found in the changed files.

Advisory only — this automated result does not count as a GitHub approval.

Review tier: Lite

[dgarske]

@miyazakh please resolve merge conflicts

[miyazakh]

@dgarske
Tested on PICO-IMX8MM (BL33 and RAM-boot). I have no QuadMax, so could you
regression-test b1c7e4f6 and 176f6c9c there?

[dgarske]

Regression-tested the shared uSDHC shim, the identity MMU and the SDMA cache maintenance on an i.MX 8QuadMax MEK, comparing master against this PR merged onto master. The MEK showed no regression:

• RAM-boot with the bundled test-app over SDP: same output as master.
• DISK_SDCARD=1 with SDMA, and with IMX8QM_SDHCI_PIO=1: GPT, A/B selection and verify all match master.
• DISK_SDCARD=1 IMX8QM_MMU=1 EL2_HYPERVISOR=1 BOOT_EL1=1 with a signed Linux FIT: verifies, boots to a login with all 6 cores up, and never prints the new unaligned-DMA warning.
• imx8qm, imx95-a55 (including stage1) and imx8mm all build, and unit-imx8qm-usdhc-shim passes.

Two optional notes on the new code:

1. invalidate_dcache_range discards whole lines, so a caller passing a range that is not line-aligned loses neighbouring data. The uSDHC path warns about this; other future callers will not. Consider a comment on the prototype in include/aarch64_arch.h.
2. el2_idmap_enable invalidates by set/way at EL2 while BL31 is resident below BL33. That is safe on A53/A72 because they perform a Non-secure DC ISW as clean and invalidate, but it is core-specific and worth one line of comment.

Two pre-existing issues hit while testing, not caused by this PR, for a follow-up:

• tools/scripts/imx8qm/imx8qm-flash.sh sdp runs uuu -b sdps, which uuu 1.5.243 rejects ("sdps is not built-in script"). uuu SDPS: boot -f flash.bin works.
• make clean leaves the wolfSSL objects under lib/wolfssl/wolfcrypt/src, including the ARMv8 asm ones. Switching between configs without deleting them can fail to link (Transform_Sha512_Len_neon undefined) or silently link objects built for the previous config.

[miyazakh]

Thanks for the regression test on the MEK.
Added both comments in 01c4cb1 (invalidate_dcache_range alignment note on the
prototype, and the BL31-resident set/way note in el2_idmap_enable).