/*************************************************************************** * Copyright (c) 2024 Microsoft Corporation * Copyright (c) 2026-present Eclipse ThreadX contributors * * This program and the accompanying materials are made available under the * terms of the MIT License which is available at * https://opensource.org/licenses/MIT. * * SPDX-License-Identifier: MIT **************************************************************************/ /**************************************************************************/ /**************************************************************************/ /** */ /** ThreadX Component */ /** */ /** Thread */ /** */ /**************************************************************************/ /**************************************************************************/ #ifdef TX_INCLUDE_USER_DEFINE_FILE #include "tx_user.h" #endif /**************************************************************************/ /* */ /* FUNCTION RELEASE */ /* */ /* _tx_thread_schedule Cortex-M23/GNU */ /* 6.2.1 */ /* AUTHOR */ /* */ /* Scott Larson, Microsoft Corporation */ /* */ /* DESCRIPTION */ /* */ /* This function waits for a thread control block pointer to appear in */ /* the _tx_thread_execute_ptr variable. Once a thread pointer appears */ /* in the variable, the corresponding thread is resumed. */ /* */ /* INPUT */ /* */ /* None */ /* */ /* OUTPUT */ /* */ /* None */ /* */ /* CALLS */ /* */ /* None */ /* */ /* CALLED BY */ /* */ /* _tx_initialize_kernel_enter ThreadX entry function */ /* _tx_thread_system_return Return to system from thread */ /* */ /**************************************************************************/ // VOID _tx_thread_schedule(VOID) // { .section .text .balign 4 .syntax unified .eabi_attribute Tag_ABI_align_preserved, 1 .global _tx_thread_schedule .thumb_func .type _tx_thread_schedule, function _tx_thread_schedule: /* This function should only ever be called on Cortex-M from the first schedule request. Subsequent scheduling occurs from the PendSV handling routine below. */ /* Clear the preempt-disable flag to enable rescheduling after initialization on Cortex-M targets. */ MOVW r0, #0 // Build value for TX_FALSE LDR r2, =_tx_thread_preempt_disable // Build address of preempt disable flag STR r0, [r2, #0] // Clear preempt disable flag /* Enable interrupts */ CPSIE i /* Enter the scheduler for the first time. */ LDR r0, =0x10000000 // Load PENDSVSET bit LDR r1, =0xE000ED04 // Load ICSR address STR r0, [r1] // Set PENDSVBIT in ICSR DSB // Complete all memory accesses ISB // Flush pipeline /* Wait here for the PendSV to take place. */ __tx_wait_here: B __tx_wait_here // Wait for the PendSV to happen // } /* Generic context switching PendSV handler. */ .section .text .balign 4 .syntax unified .eabi_attribute Tag_ABI_align_preserved, 1 .global PendSV_Handler .thumb_func .type PendSV_Handler, function /* Get current thread value and new thread pointer. */ PendSV_Handler: __tx_ts_handler: #if (defined(TX_ENABLE_EXECUTION_CHANGE_NOTIFY) || defined(TX_EXECUTION_PROFILE_ENABLE)) /* Call the thread exit function to indicate the thread is no longer executing. */ CPSID i // Disable interrupts PUSH {r0, lr} // Save LR (and r0 just for alignment) BL _tx_execution_thread_exit // Call the thread exit function POP {r0, r1} // Recover LR MOV lr, r1 // CPSIE i // Enable interrupts #endif LDR r0, =_tx_thread_current_ptr // Build current thread pointer address LDR r2, =_tx_thread_execute_ptr // Build execute thread pointer address MOVW r3, #0 // Build NULL value LDR r1, [r0] // Pickup current thread pointer /* Determine if there is a current thread to finish preserving. */ CBZ r1, __tx_ts_new // If NULL, skip preservation /* Recover PSP and preserve current thread context. */ STR r3, [r0] // Set _tx_thread_current_ptr to NULL MRS r3, PSP // Pickup PSP pointer (thread's stack pointer) SUBS r3, r3, #16 // Allocate stack space STM r3!, {r4-r7} // Save r4-r7 (M4 Instruction: STMDB r12!, {r4-r11}) MOV r4, r8 // Copy r8-r11 to multisave registers MOV r5, r9 MOV r6, r10 MOV r7, r11 SUBS r3, r3, #32 // Allocate stack space STM r3!, {r4-r7} // Save r8-r11 SUBS r3, r3, #20 // Allocate stack space MOV r5, lr // Copy lr to saveable register STR r5, [r3] // Save lr on the stack STR r3, [r1, #8] // Save the thread stack pointer #if (!defined(TX_SINGLE_MODE_SECURE) && !defined(TX_SINGLE_MODE_NON_SECURE)) // Save secure context LDR r5, =0x90 // Secure stack index offset LDR r5, [r1, r5] // Load secure stack index CBZ r5, _skip_secure_save // Skip save if there is no secure context PUSH {r0-r3} // Save scratch registers MOV r0, r1 // Move thread ptr to r0 BL _tx_thread_secure_stack_context_save // Save secure stack POP {r0-r3} // Restore secure registers _skip_secure_save: #endif /* Determine if time-slice is active. If it isn't, skip time handling processing. */ LDR r4, =_tx_timer_time_slice // Build address of time-slice variable LDR r5, [r4] // Pickup current time-slice CBZ r5, __tx_ts_new // If not active, skip processing /* Time-slice is active, save the current thread's time-slice and clear the global time-slice variable. */ STR r5, [r1, #24] // Save current time-slice /* Clear the global time-slice. */ MOVW r5, #0 // Build clear value STR r5, [r4] // Clear time-slice /* Executing thread is now completely preserved!!! */ __tx_ts_new: /* Now we are looking for a new thread to execute! */ CPSID i // Disable interrupts LDR r1, [r2] // Is there another thread ready to execute? CBZ r1, __tx_ts_wait // No, skip to the wait processing /* Yes, another thread is ready for else, make the current thread the new thread. */ STR r1, [r0] // Setup the current thread pointer to the new thread CPSIE i // Enable interrupts /* Increment the thread run count. */ __tx_ts_restore: LDR r7, [r1, #4] // Pickup the current thread run count LDR r4, =_tx_timer_time_slice // Build address of time-slice variable LDR r5, [r1, #24] // Pickup thread's current time-slice ADDS r7, r7, #1 // Increment the thread run count STR r7, [r1, #4] // Store the new run count /* Setup global time-slice with thread's current time-slice. */ STR r5, [r4] // Setup global time-slice #if (defined(TX_ENABLE_EXECUTION_CHANGE_NOTIFY) || defined(TX_EXECUTION_PROFILE_ENABLE)) /* Call the thread entry function to indicate the thread is executing. */ PUSH {r0, r1} // Save r0 and r1 BL _tx_execution_thread_enter // Call the thread execution enter function POP {r0, r1} // Recover r0 and r1 #endif #if (!defined(TX_SINGLE_MODE_SECURE) && !defined(TX_SINGLE_MODE_NON_SECURE)) // Restore secure context LDR r5, =0x90 // Secure stack index offset LDR r0, [r1, r5] // Load secure stack index CBZ r0, _skip_secure_restore // Skip restore if there is no secure context PUSH {r0, r1} // Save r1 (and dummy r0) MOV r0, r1 // Move thread ptr to r0 BL _tx_thread_secure_stack_context_restore // Restore secure stack POP {r0, r1} // Restore r1 (and dummy r0) _skip_secure_restore: #endif /* Restore the thread context and PSP. */ #ifdef TX_SINGLE_MODE_SECURE // There are only stack limit registers in secure mode on the M23 LDR r3, [r1, #12] // Get stack start MSR PSPLIM, r3 // Set stack limit #endif LDR r3, [r1, #8] // Pickup thread's stack pointer LDR r5, [r3] // Recover saved LR ADDS r3, r3, #4 // Position past LR MOV lr, r5 // Restore LR LDM r3!, {r4-r7} // Recover thread's registers (r8-r11) MOV r11, r7 MOV r10, r6 MOV r9, r5 MOV r8, r4 LDM r3!, {r4-r7} // Recover thread's registers (r4-r7) MSR PSP, r3 // Setup the thread's stack pointer BX lr // Return to thread! /* The following is the idle wait processing... in this case, no threads are ready for execution and the system will simply be idle until an interrupt occurs that makes a thread ready. Note that interrupts are disabled to allow use of WFI for waiting for a thread to arrive. */ __tx_ts_wait: CPSID i // Disable interrupts LDR r1, [r2] // Pickup the next thread to execute pointer STR r1, [r0] // Store it in the current pointer CBNZ r1, __tx_ts_ready // If non-NULL, a new thread is ready! #ifdef TX_LOW_POWER PUSH {r0-r3} BL tx_low_power_enter // Possibly enter low power mode POP {r0-r3} #endif #ifdef TX_ENABLE_WFI DSB // Ensure no outstanding memory transactions WFI // Wait for interrupt ISB // Ensure pipeline is flushed #endif #ifdef TX_LOW_POWER PUSH {r0-r3} BL tx_low_power_exit // Exit low power mode POP {r0-r3} #endif CPSIE i // Enable interrupts B __tx_ts_wait // Loop to continue waiting /* At this point, we have a new thread ready to go. Clear any newly pended PendSV - since we are already in the handler! */ __tx_ts_ready: LDR r7, =0x08000000 // Build clear PendSV value LDR r5, =0xE000ED04 // Build ICSR address STR r7, [r5] // Clear any PendSV /* Re-enable interrupts and restore new thread. */ CPSIE i // Enable interrupts B __tx_ts_restore // Restore the thread // } #if (!defined(TX_SINGLE_MODE_SECURE) && !defined(TX_SINGLE_MODE_NON_SECURE)) // SVC_Handler is not needed when ThreadX is running in single mode. .section .text .balign 4 .syntax unified .eabi_attribute Tag_ABI_align_preserved, 1 .global SVC_Handler .thumb_func .type SVC_Handler, function SVC_Handler: MOV r0, lr MOVS r1, #0x04 TST r1, r0 // Determine return stack from EXC_RETURN bit 2 BEQ _tx_load_msp MRS r0, PSP // Get PSP if return stack is PSP B _tx_get_svc _tx_load_msp: MRS r0, MSP // Get MSP if return stack is MSP _tx_get_svc: LDR r1, [r0,#24] // Load saved PC from stack LDR r3, =-2 LDRB r1, [r1,r3] // Load SVC number CMP r1, #1 // Is it a secure stack allocate request? BEQ _tx_svc_secure_alloc // Yes, go there CMP r1, #2 // Is it a secure stack free request? BEQ _tx_svc_secure_free // Yes, go there CMP r1, #3 // Is it a secure stack init request? BEQ _tx_svc_secure_init // Yes, go there // Unknown SVC argument - just return BX lr _tx_svc_secure_alloc: PUSH {r0, lr} // Save SP and EXC_RETURN LDM r0, {r0-r3} // Load function parameters from stack BL _tx_thread_secure_mode_stack_allocate POP {r1, r2} // Restore SP and EXC_RETURN STR r0, [r1] // Store function return value MOV lr, r2 BX lr _tx_svc_secure_free: PUSH {r0, lr} // Save SP and EXC_RETURN LDM r0, {r0-r3} // Load function parameters from stack BL _tx_thread_secure_mode_stack_free POP {r1, r2} // Restore SP and EXC_RETURN STR r0, [r1] // Store function return value MOV lr, r2 BX lr _tx_svc_secure_init: PUSH {r0,lr} // Save SP and EXC_RETURN BL _tx_thread_secure_mode_stack_initialize POP {r1, r2} // Restore SP and EXC_RETURN MOV lr, r2 BX lr #endif // End of ifndef TX_SINGLE_MODE_SECURE, TX_SINGLE_MODE_NON_SECURE .end