[dgarske]

Description

Adds TARGET=s32g2 for the NXP S32G274A on the S32G-VNP-GLDBOX (RDB2). wolfBoot is the Boot ROM's application image: it runs from SRAM at EL3 in place of U-Boot, brings the SoC up, verifies a signed FIT and enters Linux at EL2.

What it adds

• hal/s32g2.c, hal/s32g2.h, hal/s32g2.ld - HAL: LINFlexD console, VR5510 watchdog over I2C, clock tree, Ncore, EL3 identity MMU, GICv3, secondary cores on a spin table, QuadSPI NOR driver behind the ext_flash API, device tree fixups
• hal/s32g2_ddr.c - LPDDR4 controller and PHY bring-up. The board's register tables and the Synopsys PHY training firmware are not in the tree: tools/scripts/s32g2/s32g2-ddr-blob.py packs them from an NXP BSP U-Boot checkout into a blob the build links in
• config/examples/s32g2-goldbox.config - boot from SD or eMMC with two FIT file slots; s32g2-goldbox-qspi.config - boot from QuadSPI NOR with BOOT/UPDATE partitions in the NOR
• tools/scripts/s32g2/ - Boot ROM image writer (IVT, DCD, QuadSPI parameter block) and FIT build script
• docs/Targets.md, CI build jobs for each variant

Touches shared code

• src/boot_aarch64_start.S, src/boot_aarch64.c - S32G2 blocks only: SRAM ECC initialisation before the first store, EL3 fault vectors, secondary core entry, EL3 to EL2 handoff
• hal/imx_usdhc_sdhci.c - the shared uSDHC shim now also serves S32G2
• src/update_disk.c - ALLOW_DOWNGRADE=1 no longer fails to build on an unused variable

Testing

Validated on a GoldBox (S32G274A rev 2.1, RDB2 rev D): Boot ROM boot from SD and from QuadSPI NOR, the signed FIT read from SD (both file slots), eMMC and the NOR BOOT partition, Linux 5.4 (BSP29) to a login prompt with four cores. The ALLOW_DOWNGRADE=1 fix is build-tested only.