The MPU region dedicated for SDRAM for STM32F4 SoCs family was set to 16MB, but STM32F429 Evaluation board have 32MB of SDRAM.

When kernel starts, only first 16MB of SDRAM are configured with XN (eXecute Never) bit disabled, whereas kernel is using 32MB. To avoid such situation in the future, extend this MPU region to 512MB as for STM32F7/H7.

It fixes the following user land exception on STM32F429 Evaluation board :

[ 1.713002] VFS: Mounted root (ext4 filesystem) readonly on device 179:2. [ 1.722605] devtmpfs: mounted [ 1.733057] Freeing unused kernel memory: 72K [ 1.737622] This architecture does not have kernel memory protection. [ 1.744070] Run /sbin/init as init process [ 1.906850] [ 1.906850] Unhandled exception: IPSR = 00000004 LR = fffffffd [ 1.914282] CPU: 0 PID: 1 Comm: init Not tainted 5.1.0-00002-gcf9ca5719954 #6 [ 1.921433] Hardware name: STM32 (Device Tree Support) [ 1.926601] PC is at 0x1a00b64 [ 1.929642] LR is at (null) [ 1.932669] pc : [<01a00b64>] lr : [<00000000>] psr: 01000000 [ 1.938993] sp : 01a5cfb0 ip : 00000000 fp : 00000000 [ 1.944269] r10: 01a43b00 r9 : 00000000 r8 : 00000000 [ 1.949564] r7 : 00000000 r6 : 00000000 r5 : 00000000 r4 : 00000000 [ 1.956168] r3 : 00000000 r2 : 00000000 r1 : 00000000 r0 : 00000000 [ 1.962701] xPSR: 01000000 [ 1.965506] CPU: 0 PID: 1 Comm: init Not tainted 5.1.0-00002-gcf9ca5719954 #6 [ 1.972658] Hardware name: STM32 (Device Tree Support) [ 1.978132] [<0000c009>] (unwind_backtrace) from [<0000b24f>] (show_stack+0xb/0xc) [ 1.986024] [<0000b24f>] (show_stack) from [<0000b947>] (__invalid_entry+0x4b/0x4c)

Signed-off-by: Patrice Chotard patrice.chotard@st.com

---

Changes in v2: - Increase SDRAM MPU region from 32 to 512MB

arch/arm/mach-stm32/soc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mach-stm32/soc.c b/arch/arm/mach-stm32/soc.c index 6ae31d3a1f..41338a1a33 100644 --- a/arch/arm/mach-stm32/soc.c +++ b/arch/arm/mach-stm32/soc.c @@ -18,7 +18,7 @@ int arch_cpu_init(void) */ #if defined(CONFIG_STM32F4) { 0x00000000, REGION_0, XN_DIS, PRIV_RW_USR_RW, - O_I_WB_RD_WR_ALLOC, REGION_16MB }, + O_I_WB_RD_WR_ALLOC, REGION_512MB }, #endif

{ 0x90000000, REGION_1, XN_DIS, PRIV_RW_USR_RW,