[PATCH] ARM: stm32: Initialize TAMP_SMCR BKP..PROT fields on STM32MP15xx

[Patrice CHOTARD]

On 4/14/24 20:39, Marek Vasut wrote:
> In case of an OTP-CLOSED STM32MP15xx system, the CPU core 1 cannot be
> released from endless loop in BootROM only by populating TAMP BKPxR 4
> and 5 with magic and branch address and sending SGI0 interrupt from
> core 0 to core 1 twice. TAMP_SMCR BKP..PROT fields must be initialized
> as well to release the core 1 from endless loop during the second SGI0
> handling on core 1. Initialize TAMP_SMCR to protect the first 16 backup
> registers, the ones which contain the core 1 magic, branch address and
> boot information.
> 
> This requirement seems to be undocumented, therefore it was necessary
> to trace and analyze the STM32MP15xx BootROM using OpenOCD and objdump.
> Ultimately, it turns out that a certain BootROM function reads out the
> TAMP_SMCR register and tests whether the BKP..PROT fields are non-zero.
> If they are zero, the BootROM code again waits for SGI0 using WFI, else
> the execution moves forward until it reaches handoff to the TAMP BKPxR 5
> branch address.
> 
> This fixes CPU core 1 release using U-Boot PSCI implementation on an
> OTP-CLOSED system, i.e. system with fuse 0 bit 6 set.
> 
> Signed-off-by: Marek Vasut <marex at denx.de>
> ---
> Cc: Igor Opaniuk <igor.opaniuk at foundries.io>
> Cc: Patrice Chotard <patrice.chotard at foss.st.com>
> Cc: Patrick Delaunay <patrick.delaunay at foss.st.com>
> Cc: Simon Glass <sjg at chromium.org
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: u-boot at dh-electronics.com
> Cc: uboot-stm32 at st-md-mailman.stormreply.com
> ---
>  arch/arm/mach-stm32mp/stm32mp1/stm32mp15x.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/arch/arm/mach-stm32mp/stm32mp1/stm32mp15x.c b/arch/arm/mach-stm32mp/stm32mp1/stm32mp15x.c
> index dd99150fbc2..138a6d6b614 100644
> --- a/arch/arm/mach-stm32mp/stm32mp1/stm32mp15x.c
> +++ b/arch/arm/mach-stm32mp/stm32mp1/stm32mp15x.c
> @@ -14,6 +14,7 @@
>  #include <asm/arch/sys_proto.h>
>  #include <dm/device.h>
>  #include <dm/uclass.h>
> +#include <linux/bitfield.h>
>  
>  /* RCC register */
>  #define RCC_TZCR		(STM32_RCC_BASE + 0x00)
> @@ -41,6 +42,9 @@
>  #define TZC_REGION_ID_ACCESS0	(STM32_TZC_BASE + 0x114)
>  
>  #define TAMP_CR1		(STM32_TAMP_BASE + 0x00)
> +#define TAMP_SMCR		(STM32_TAMP_BASE + 0x20)
> +#define TAMP_SMCR_BKPRWDPROT	GENMASK(7, 0)
> +#define TAMP_SMCR_BKPWDPROT	GENMASK(23, 16)
>  
>  #define PWR_CR1			(STM32_PWR_BASE + 0x00)
>  #define PWR_MCUCR		(STM32_PWR_BASE + 0x14)
> @@ -136,6 +140,18 @@ static void security_init(void)
>  	 */
>  	writel(0x0, TAMP_CR1);
>  
> +	/*
> +	 * TAMP: Configure non-zero secure protection settings. This is
> +	 * checked by BootROM function 35ac on OTP-CLOSED device during
> +	 * CPU core 1 release from endless loop. If secure protection
> +	 * fields are zero, the core 1 is not released from endless
> +	 * loop on second SGI0.
> +	 */
> +	clrsetbits_le32(TAMP_SMCR,
> +			TAMP_SMCR_BKPRWDPROT | TAMP_SMCR_BKPRWDPROT,

Hi Marek

there is a typo, you used twice TAMP_SMCR_BKPRWDPROT :

TAMP_SMCR_BKPRWDPROT | TAMP_SMCR_BKPRWDPROT  => TAMP_SMCR_BKPRWDPROT | TAMP_SMCR_BKPWDPROT 
                                    ^~~~~                 

Patrice

> +			FIELD_PREP(TAMP_SMCR_BKPRWDPROT, 0x10) |
> +			FIELD_PREP(TAMP_SMCR_BKPWDPROT, 0x10));
> +
>  	/* GPIOZ: deactivate the security */
>  	writel(BIT(0), RCC_MP_AHB5ENSETR);
>  	writel(0x0, GPIOZ_SECCFGR);