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Disable write buffer in debug builds (M3/M4) #8655

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Merged
merged 2 commits into from
Dec 17, 2018
Merged

Disable write buffer in debug builds (M3/M4) #8655

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f04904c
CM3: Make ACTLR bit definitions conditional
kjbracey Dec 13, 2018
bd413f1
Disable write buffer in debug builds (M3/M4)
kjbracey Nov 6, 2018
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3 changes: 2 additions & 1 deletion cmsis/TARGET_CORTEX_M/core_cm3.h
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Original file line number Diff line number Diff line change
Expand Up @@ -668,7 +668,7 @@ typedef struct
#define SCnSCB_ICTR_INTLINESNUM_Msk (0xFUL /*<< SCnSCB_ICTR_INTLINESNUM_Pos*/) /*!< ICTR: INTLINESNUM Mask */

/* Auxiliary Control Register Definitions */

#if defined (__CM3_REV) && (__CM3_REV >= 0x200U)
#define SCnSCB_ACTLR_DISFOLD_Pos 2U /*!< ACTLR: DISFOLD Position */
#define SCnSCB_ACTLR_DISFOLD_Msk (1UL << SCnSCB_ACTLR_DISFOLD_Pos) /*!< ACTLR: DISFOLD Mask */

Expand All @@ -677,6 +677,7 @@ typedef struct

#define SCnSCB_ACTLR_DISMCYCINT_Pos 0U /*!< ACTLR: DISMCYCINT Position */
#define SCnSCB_ACTLR_DISMCYCINT_Msk (1UL /*<< SCnSCB_ACTLR_DISMCYCINT_Pos*/) /*!< ACTLR: DISMCYCINT Mask */
#endif

/*@} end of group CMSIS_SCnotSCB */

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11 changes: 11 additions & 0 deletions platform/mbed_application.c
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Expand Up @@ -71,6 +71,17 @@ void mbed_start_application(uintptr_t address)
powerdown_scb(address);
mbed_mpu_free();

#ifdef MBED_DEBUG
// Configs to make debugging easier
#ifdef SCnSCB_ACTLR_DISDEFWBUF_Msk
// Disable write buffer to make BusFaults (eg write to ROM via NULL pointer) precise.
// Possible on Cortex-M3 and M4, not on M0, M7 or M33.
// Would be less necessary if ROM was write-protected in MPU to give a
// precise MemManage exception.
SCnSCB->ACTLR |= SCnSCB_ACTLR_DISDEFWBUF_Msk;
#endif
#endif

sp = *((void **)address + 0);
pc = *((void **)address + 1);
start_new_application(sp, pc);
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