From a24daa78d0fecce4c74c43789ea6c7b99c4d9ccf Mon Sep 17 00:00:00 2001
From: Andrey Mironov <diehertz@gmail.com>
Date: Sun, 4 Mar 2018 12:45:40 +0300
Subject: [PATCH] Fixed possibility of getting stuck in F7 bootloader mode
 (#5370)

---
 src/main/drivers/system_stm32f7xx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/main/drivers/system_stm32f7xx.c b/src/main/drivers/system_stm32f7xx.c
index bfe8039dde..8bbbe3af98 100644
--- a/src/main/drivers/system_stm32f7xx.c
+++ b/src/main/drivers/system_stm32f7xx.c
@@ -197,6 +197,9 @@ void checkForBootLoaderRequest(void)
     bt = (*(__IO uint32_t *) (BKPSRAM_BASE + 4)) ;
     if ( bt == 0xDEADBEEF ) {
         (*(__IO uint32_t *) (BKPSRAM_BASE + 4)) =  0xCAFEFEED; // Reset our trigger
+        // Backup SRAM is write-back by default, ensure value actually reaches memory
+        // Another solution would be marking BKPSRAM as write-through in Memory Protection Unit settings
+        SCB_CleanDCache_by_Addr((uint32_t *) (BKPSRAM_BASE + 4), sizeof(uint32_t));
 
         void (*SysMemBootJump)(void);
         __SYSCFG_CLK_ENABLE();