Add STM32C5 target (NUCLEO-C5A3ZG)

Author: dgarske

.github/workflows/test-configs.yml

@@ -542,6 +542,12 @@ jobs:
       arch: arm
       config-file: ./config/examples/stm32u3.config
 
+  stm32c5_test:
+    uses: ./.github/workflows/test-build.yml
+    with:
+      arch: arm
+      config-file: ./config/examples/stm32c5.config
+
   stm32u5_nonsecure_dualbank_test:
     uses: ./.github/workflows/test-build.yml
     with:

arch.mk

@@ -264,6 +264,15 @@ ifeq ($(ARCH),ARM)
     SPI_TARGET=stm32
   endif
 
+  ifeq ($(TARGET),stm32c5)
+    CORTEX_M33=1
+    CFLAGS+=-Ihal
+    ARCH_FLASH_OFFSET=0x08000000
+    WOLFBOOT_ORIGIN=0x08000000
+    LSCRIPT_IN=hal/$(TARGET).ld
+    SPI_TARGET=stm32
+  endif
+
   ifeq ($(TARGET),stm32h5)
     CORTEX_M33=1
     CFLAGS+=-Ihal

config/examples/stm32c5.config

@@ -0,0 +1,31 @@
+ARCH?=ARM
+TZEN?=0
+TARGET?=stm32c5
+SIGN?=ECC256
+HASH?=SHA256
+DEBUG?=0
+VTOR?=1
+CORTEX_M0?=0
+CORTEX_M33?=1
+NO_ASM?=0
+NO_MPU=1
+EXT_FLASH?=0
+SPI_FLASH?=0
+ALLOW_DOWNGRADE?=0
+NVM_FLASH_WRITEONCE?=1
+WOLFBOOT_VERSION?=1
+V?=0
+SPMATH?=1
+RAM_CODE?=1
+DUALBANK_SWAP?=0
+# Flash layout for dual-bank (2x512KB, 8KB pages, 1MB total):
+#   Bank 1 (0x08000000): wolfBoot (64KB) + BOOT partition (448KB)
+#   Bank 2 (0x08080000): UPDATE partition (448KB) + SWAP (8KB)
+WOLFBOOT_SECTOR_SIZE?=0x2000
+WOLFBOOT_PARTITION_SIZE?=0x70000
+WOLFBOOT_PARTITION_BOOT_ADDRESS?=0x08010000
+WOLFBOOT_PARTITION_UPDATE_ADDRESS?=0x08080000
+WOLFBOOT_PARTITION_SWAP_ADDRESS?=0x080F0000
+FLAGS_HOME=0
+DISABLE_BACKUP=0
+DEBUG_UART=1

docs/Targets.md

@@ -39,6 +39,7 @@ This README describes configuration of supported targets.
 * [Renesas RZN2L](#renesas-rzn2l)
 * [SiFive HiFive1 RISC-V](#sifive-hifive1-risc-v)
 * [STM32C0](#stm32c0)
+* [STM32C5](#stm32c5)
 * [STM32F1](#stm32f1)
 * [STM32F4](#stm32f4)
 * [STM32F7](#stm32f7)
@@ -1779,6 +1780,117 @@ the new image. LD2 transitions from the slow (v1) blink to the fast
 transition.
 
 
+## STM32C5
+
+The STM32C5 family (for example the STM32C5A3ZGT6 on NUCLEO-C5A3ZG) is
+a mainstream Cortex-M33 part **without TrustZone**, so the port is
+single-image only (no `-tz` or `-ns` variants). On the -ZG variant:
+1 MB internal flash, 256 KB SRAM, 8 KB pages, **128-bit (quad-word)
+flash write quantum** with per-quad-word ECC.
+
+The HAL writes flash in 16-byte aligned quad-words. When wolfBoot
+asks for a smaller or unaligned write, the HAL reads the surrounding
+flash and merges so each programmed quad-word is a complete ECC
+block - sub-quad-word writes leave ECC undefined and reads come back
+with bit-flipped "corrected" data.
+
+### Flash layout (stm32c5.config)
+
+Dual-bank flash (2 x 512 KB, 8 KB pages). Bank 1 holds wolfBoot +
+BOOT, bank 2 holds UPDATE + SWAP:
+
+```
+Bank 1:
+  0x08000000 - 0x0800FFFF  wolfBoot bootloader   (64 KB)
+  0x08010000 - 0x0807FFFF  BOOT partition        (0x70000, 448 KB)
+Bank 2:
+  0x08080000 - 0x080EFFFF  UPDATE partition      (0x70000, 448 KB)
+  0x080F0000 - 0x080F1FFF  SWAP sector           (8 KB)
+```
+
+### Clock and UART
+
+The reset SYSCLK is **HSIDIV3 = HSIS / 3 = 16 MHz** (RCC_CFGR1.SW=0
+selects HSIDIV3, RCC_CR1 reset value 0x22 = HSIDIV3ON | HSIDIV3RDY).
+wolfBoot brings SYSCLK to **144 MHz HCLK** in `clock_init()` via the
+PSIS clock chain (HSE 48 MHz reference -> PSI ref=48 MHz / out=144 MHz
+-> PSIS), with all bus prescalers /1 (PCLK1 = PCLK2 = PCLK3 = 144 MHz),
+flash 4 wait states and WRHIGHFREQ programming delay = 2.
+
+By default (`WOLFBOOT_RESTORE_CLOCK` set in `options.mk`),
+`hal_prepare_boot()` switches SYSCLK back to HSIDIV3 before handoff
+but **leaves PSIS, PSI and HSE running**. The loaded firmware's own
+`clock_psi_on()` then just pushes SYSCLK back from HSIDIV3 to PSIS -
+the HSE/PSI configuration it would have written is already in place,
+so it skips the HSE startup wait and the PSI reconfiguration entirely.
+This mirrors ST's `HAL_RCC_ResetSystemClock()` (the lightweight
+restore) rather than the full `HAL_RCC_Reset()`. Disabling HSE in
+`hal_prepare_boot()` and forcing the loaded firmware to re-enable it
+on a back-to-back cycle is not reliable on this part; the lightweight
+restore avoids that path entirely. Pass `WOLFBOOT_RESTORE_CLOCK=0`
+to skip the SYSCLK switch entirely and inherit PSIS @ 144 MHz directly.
+
+UART is always available in the test-app and enabled in wolfBoot via
+`DEBUG_UART=1` (on by default in the example config). USART2_BRR is
+computed for PCLK1 = 144 MHz. The NUCLEO-C5A3ZG ST-LINK virtual COM
+port is wired to MCU pins 36/37 (PA2/PA3) - **USART2** on AF7, 115200
+8N1, **not USART1 on PA9/PA10** (PA9/PA10 only reach the Arduino
+headers).
+
+### Building
+
+```sh
+cp config/examples/stm32c5.config .config
+make clean
+make
+```
+
+Default signing scheme is ECC256 + SHA256. Produces `wolfboot.bin`
+(~25 KB), `test-app/image_v1_signed.bin`, and `factory.bin` (BL +
+signed v1).
+
+### Flashing
+
+Use `STM32_Programmer_CLI` (from STM32CubeIDE or STM32CubeProgrammer
+v2.22+). pyocd has no STM32C5 target as of this writing. The C5
+debug access port is AP2; `mode=UR` (under-reset) is the most
+reliable connect mode while a previous image is running.
+
+```sh
+STM32_Programmer_CLI -c port=swd mode=UR -e all \
+    -d factory.bin 0x08000000 -v -rst
+```
+
+The test app blinks LD2 (PG1, **active low**): five slow blinks on
+v1 then it triggers an update and resets; v2 blinks fast forever
+once `wolfBoot_success()` is acknowledged.
+
+### Testing an Update
+
+Sign the test application as version 2 and flash it directly to the
+update partition:
+
+```sh
+./tools/keytools/sign --ecc256 --sha256 \
+    test-app/image.bin wolfboot_signing_private_key.der 2
+STM32_Programmer_CLI -c port=swd mode=UR \
+    -d test-app/image_v2_signed.bin 0x08080000 -v -rst
+```
+
+On reset wolfBoot detects the staged v2, the v1 test-app calls
+`wolfBoot_update_trigger()` after its blink sequence and resets,
+wolfBoot performs the bank-to-bank swap, and v2 boots. With
+`DEBUG_UART=1` the UART log shows:
+
+```
+Booting version: 0x1
+TEST APP / App version: 1 / triggering update -> reset
+... swap output ...
+Booting version: 0x2
+TEST APP / App version: 2 / update OK -- success confirmed
+```
+
+
 ## STM32H5
 
 Like [STM32L5](#stm32l5) and [STM32U5](#stm32u5), STM32H5 support is also demonstrated