[U-Boot] [PATCH] mach-stm32: Use default memory map as background region

[Vikas Manocha]

Hi Patrice,

On 02/28/2018 08:15 AM, patrice.chotard at st.com wrote:
> From: Patrice Chotard <patrice.chotard at st.com>
> 
> On linux kernel side, on STM32F7 and STM32H7 SoCs, DMA requires
> uncachable regions. These regions are defined in DT.
> Since kernel linux v4.15, on ARMv7-M Cortex, kernel is able
> to configure MPU regions depending on DT settings.
> 
> As kernel is able to configure MPU, this allows to remove
> MPU region settings in bootloader.

I am not sure default configuration is same of all cortex-M variants which might lead to referring to different docs.
Regardless, It is good idea to configure MPU here instead of depending on default config, here code is making the picture clear.

Cheers,
Vikas

> 
> On Cortex M processors, MPU allows to use a default memory map.
> (see B3.5.4 MPU Control Register, MPU_CTRL in
> https://developer.arm.com/products/architecture/m-profile/docs/ddi0403/latest/armv7-m-architecture-reference-manual)
> Use the default memory map as background region for all STM32 SoCs
> family with an additional MPU region corresponding to the SDRAM area.
> 
> Signed-off-by: Patrice Chotard <patrice.chotard at st.com>
> ---
>  arch/arm/cpu/armv7m/mpu.c | 11 ++++++-----
>  arch/arm/mach-stm32/soc.c | 36 +++++++++++-------------------------
>  2 files changed, 17 insertions(+), 30 deletions(-)
> 
> diff --git a/arch/arm/cpu/armv7m/mpu.c b/arch/arm/cpu/armv7m/mpu.c
> index 8e92a33fd4dd..e4d090e5de48 100644
> --- a/arch/arm/cpu/armv7m/mpu.c
> +++ b/arch/arm/cpu/armv7m/mpu.c
> @@ -10,12 +10,13 @@
>  #include <asm/armv7m_mpu.h>
>  #include <asm/io.h>
>  
> -#define V7M_MPU_CTRL_ENABLE		(1 << 0)
> +#define V7M_MPU_CTRL_ENABLE		BIT(0)
>  #define V7M_MPU_CTRL_DISABLE		(0 << 0)
> -#define V7M_MPU_CTRL_HFNMIENA		(1 << 1)
> -#define VALID_REGION			(1 << 4)
> +#define V7M_MPU_CTRL_HFNMIENA		BIT(1)
> +#define V7M_MPU_CTRL_PRIVDEFENA		BIT(2)
> +#define VALID_REGION			BIT(4)
>  
> -#define ENABLE_REGION			(1 << 0)
> +#define ENABLE_REGION			BIT(0)
>  
>  #define AP_SHIFT			24
>  #define XN_SHIFT			28
> @@ -36,7 +37,7 @@ void disable_mpu(void)
>  
>  void enable_mpu(void)
>  {
> -	writel(V7M_MPU_CTRL_ENABLE | V7M_MPU_CTRL_HFNMIENA, &V7M_MPU->ctrl);
> +	writel(V7M_MPU_CTRL_ENABLE | V7M_MPU_CTRL_PRIVDEFENA, &V7M_MPU->ctrl);
>  
>  	/* Make sure new mpu config is effective for next memory access */
>  	dsb();
> diff --git a/arch/arm/mach-stm32/soc.c b/arch/arm/mach-stm32/soc.c
> index df20d547c500..f6fd0b2e23c6 100644
> --- a/arch/arm/mach-stm32/soc.c
> +++ b/arch/arm/mach-stm32/soc.c
> @@ -15,35 +15,21 @@ int arch_cpu_init(void)
>  
>  	struct mpu_region_config stm32_region_config[] = {
>  		/*
> -		 * Make all 4GB cacheable & executable. We are overriding it
> -		 * with next region for any requirement. e.g. below region1,
> -		 * 2 etc.
> -		 * In other words, the area not coming in following
> -		 * regions configuration is the one configured here in region_0
> -		 * (cacheable & executable).
> +		 * Make SDRAM area cacheable & executable.
>  		 */
> +#if defined(CONFIG_STM32F4)
>  		{ 0x00000000, REGION_0, XN_DIS, PRIV_RW_USR_RW,
> -		O_I_WB_RD_WR_ALLOC, REGION_4GB },
> -
> -		/* armv7m code area */
> -		{ 0x00000000, REGION_1, XN_DIS, PRIV_RW_USR_RW,
> -		STRONG_ORDER, REGION_512MB },
> -
> -		/* Device area : Not executable */
> -		{ 0x40000000, REGION_2, XN_EN, PRIV_RW_USR_RW,
> -		DEVICE_NON_SHARED, REGION_512MB },
> +		O_I_WB_RD_WR_ALLOC, REGION_16MB },
> +#endif
>  
> -		/*
> -		 * Armv7m fixed configuration: strongly ordered & not
> -		 * executable, not cacheable
> -		 */
> -		{ 0xE0000000, REGION_3, XN_EN, PRIV_RW_USR_RW,
> -		STRONG_ORDER, REGION_512MB },
> +#if defined(CONFIG_STM32F7)
> +		{ 0xC0000000, REGION_0, XN_DIS, PRIV_RW_USR_RW,
> +		O_I_WB_RD_WR_ALLOC, REGION_16MB },
> +#endif
>  
> -#if !defined(CONFIG_STM32H7)
> -		/* Device area : Not executable */
> -		{ 0xA0000000, REGION_4, XN_EN, PRIV_RW_USR_RW,
> -		DEVICE_NON_SHARED, REGION_512MB },
> +#if defined(CONFIG_STM32H7)
> +		{ 0xD0000000, REGION_0, XN_DIS, PRIV_RW_USR_RW,
> +		O_I_WB_RD_WR_ALLOC, REGION_32MB },
>  #endif
>  	};
>  
>