Add new assembly function 'arch_very_early_init' This functions setups the power supply for STM32H7 SoC's to direct SMPS mode, which is required for some boards like the STM32H747I-DISCO in the default configuration.
If this isn't done in an early stage it cause a deadlock and also the SoC is running in a limited mode according to the TRM from the SoC. Signed-off-by: Johannes Krottmayer <johan...@krotti42.com> Cc: Patrick Delaunay <patrick.delau...@foss.st.com> Cc: Patrice Chotard <patrice.chot...@foss.st.com> --- arch/arm/mach-stm32/stm32h7/lowlevel.S | 45 ++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 arch/arm/mach-stm32/stm32h7/lowlevel.S diff --git a/arch/arm/mach-stm32/stm32h7/lowlevel.S b/arch/arm/mach-stm32/stm32h7/lowlevel.S new file mode 100644 index 00000000000..97f4e383e3b --- /dev/null +++ b/arch/arm/mach-stm32/stm32h7/lowlevel.S @@ -0,0 +1,45 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Copyright (C) 2025, Johannes Krottmayer <johan...@krotti42.com> + */ + +#include <linux/linkage.h> + +/* + * STM32H7 PWR registers + */ +#define PWR_CR3 0x5802480C +#define PWR_CR3_LDOEN 1 + +#define PWR_CSR1 0x58024804 +#define PWR_CSR1_ACTVOSRDY 13 + +ENTRY(arch_very_early_init) + /* + * Setup power supply for STM32H7 to direct SMPS mode. + * This is the default configuration from some boards + * like the SMT32H747i-DISCO. + * + * If these steps will not be done, this cause a deadlock. + */ + ldr r6, =PWR_CR3 + /* Disable LDO */ + movs r0, #1 + lsl r1, r0, #PWR_CR3_LDOEN + mvn r2, r1 + ldr r3, [r6] + and r3, r2 + str r3, [r6] + lsl r1, r0, #PWR_CSR1_ACTVOSRDY + + /* Loop until ACTVOSRDY is valid */ +1: + ldr r6, =PWR_CSR1 + ldr r3, [r6] + and r3, r1 + cmp r3, r1 + bne 1b + + /* Jump back to C runtime setup */ + bx lr +ENDPROC(arch_very_early_init) -- 2.39.5
