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Reduce SVCall priority on ARMv7-M with MPU (#1470)

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Restore the original SVCall priority for the ARMv7-M MPU ports from
before #832.  This change reduces the SVCall preemption priority from
zero (the highest) to a priority just higher than
configMAX_SYSCALL_INTERRUPT_PRIORITY (numerically lower).

---------

Co-authored-by: Gaurav-Aggarwal-AWS <33462878+aggarg@users.noreply.github.com>
This commit is contained in:
Jeff Tenney 2026-08-26 09:38:52 -07:00 • committed by GitHub
parent 92bfb86ce3
commit 7625c72410
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GPG key ID: B5690EEEBB952194
4 changed files with 23 additions and 17 deletions
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11
portable/RVDS/ARM_CM4_MPU/port.c
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@ -95,13 +95,15 @@ typedef void ( * portISR_t )( void );
#define portPERIPHERALS_START_ADDRESS 0x40000000UL
#define portPERIPHERALS_END_ADDRESS 0x5FFFFFFFUL
/* Constants required to access and manipulate the SysTick. */
/* Constants required to access and manipulate the SysTick and other FreeRTOS
* interrupts. */
#define portNVIC_SYSTICK_CLK ( 0x00000004UL )
#define portNVIC_SYSTICK_INT ( 0x00000002UL )
#define portNVIC_SYSTICK_ENABLE ( 0x00000001UL )
#define portMIN_INTERRUPT_PRIORITY ( 255UL )
#define portNVIC_PENDSV_PRI ( ( ( uint32_t ) portMIN_INTERRUPT_PRIORITY ) << 16UL )
#define portNVIC_SYSTICK_PRI ( ( ( uint32_t ) portMIN_INTERRUPT_PRIORITY ) << 24UL )
#define portNVIC_SVC_PRI ( ( ( uint32_t ) configMAX_SYSCALL_INTERRUPT_PRIORITY - 1UL ) << 24UL )
/* Constants required to manipulate the VFP. */
#define portFPCCR ( ( volatile uint32_t * ) 0xe000ef34UL ) /* Floating point context control register. */
@ -966,12 +968,11 @@ BaseType_t xPortStartScheduler( void )
}
#endif /* configASSERT_DEFINED */
/* Make PendSV and SysTick the same priority as the kernel, and the SVC
* handler highest priority so it can be used to exit a critical section
* (where lower priorities are masked). */
/* Make PendSV and SysTick the lowest priority interrupts, and configure
* SVCall for sufficient preemption priority. */
portNVIC_SHPR3_REG |= portNVIC_PENDSV_PRI;
portNVIC_SHPR3_REG |= portNVIC_SYSTICK_PRI;
portNVIC_SHPR2_REG = 0;
portNVIC_SHPR2_REG = portNVIC_SVC_PRI;
/* Configure the regions in the MPU that are common to all tasks. */
prvSetupMPU();