| /********************************************************************* |
| * (c) SEGGER Microcontroller GmbH * |
| * The Embedded Experts * |
| * www.segger.com * |
| ********************************************************************** |
| |
| -------------------------- END-OF-HEADER ----------------------------- |
| |
| File : SEGGER_RTT_ASM_ARMv7M.S |
| Purpose : Assembler implementation of RTT functions for ARMv7M |
| |
| Additional information: |
| This module is written to be assembler-independent and works with |
| GCC and clang (Embedded Studio) and IAR. |
| */ |
| |
| #define SEGGER_RTT_ASM // Used to control processed input from header file |
| #include "SEGGER_RTT.h" |
| |
| /********************************************************************* |
| * |
| * Defines, fixed |
| * |
| ********************************************************************** |
| */ |
| #define _CCIAR 0 |
| #define _CCCLANG 1 |
| |
| #if (defined __SES_ARM) || (defined __GNUC__) || (defined __clang__) |
| #define _CC_TYPE _CCCLANG |
| #define _PUB_SYM .global |
| #define _EXT_SYM .extern |
| #define _END .end |
| #define _WEAK .weak |
| #define _THUMB_FUNC .thumb_func |
| #define _THUMB_CODE .code 16 |
| #define _WORD .word |
| #define _SECTION(Sect, Type, AlignExp) .section Sect ##, "ax" |
| #define _ALIGN(Exp) .align Exp |
| #define _PLACE_LITS .ltorg |
| #define _DATA_SECT_START |
| #define _C_STARTUP _start |
| #define _STACK_END __stack_end__ |
| #define _RAMFUNC |
| // |
| // .text => Link to flash |
| // .fast => Link to RAM |
| // OtherSect => Usually link to RAM |
| // Alignment is 2^x |
| // |
| #elif defined (__IASMARM__) |
| #define _CC_TYPE _CCIAR |
| #define _PUB_SYM PUBLIC |
| #define _EXT_SYM EXTERN |
| #define _END END |
| #define _WEAK _WEAK |
| #define _THUMB_FUNC |
| #define _THUMB_CODE THUMB |
| #define _WORD DCD |
| #define _SECTION(Sect, Type, AlignExp) SECTION Sect ## : ## Type ## :REORDER:NOROOT ## (AlignExp) |
| #define _ALIGN(Exp) alignrom Exp |
| #define _PLACE_LITS |
| #define _DATA_SECT_START DATA |
| #define _C_STARTUP __iar_program_start |
| #define _STACK_END sfe(CSTACK) |
| #define _RAMFUNC SECTION_TYPE SHT_PROGBITS, SHF_WRITE | SHF_EXECINSTR |
| // |
| // .text => Link to flash |
| // .textrw => Link to RAM |
| // OtherSect => Usually link to RAM |
| // NOROOT => Allows linker to throw away the function, if not referenced |
| // Alignment is 2^x |
| // |
| #endif |
| |
| #if (_CC_TYPE == _CCIAR) |
| NAME SEGGER_RTT_ASM_ARMv7M |
| #else |
| .syntax unified |
| #endif |
| |
| #if defined (RTT_USE_ASM) && (RTT_USE_ASM == 1) |
| #define SHT_PROGBITS 0x1 |
| |
| /********************************************************************* |
| * |
| * Public / external symbols |
| * |
| ********************************************************************** |
| */ |
| |
| _EXT_SYM __aeabi_memcpy |
| _EXT_SYM __aeabi_memcpy4 |
| _EXT_SYM _SEGGER_RTT |
| |
| _PUB_SYM SEGGER_RTT_ASM_WriteSkipNoLock |
| |
| /********************************************************************* |
| * |
| * SEGGER_RTT_WriteSkipNoLock |
| * |
| * Function description |
| * Stores a specified number of characters in SEGGER RTT |
| * control block which is then read by the host. |
| * SEGGER_RTT_WriteSkipNoLock does not lock the application and |
| * skips all data, if the data does not fit into the buffer. |
| * |
| * Parameters |
| * BufferIndex Index of "Up"-buffer to be used (e.g. 0 for "Terminal"). |
| * pBuffer Pointer to character array. Does not need to point to a \0 terminated string. |
| * NumBytes Number of bytes to be stored in the SEGGER RTT control block. |
| * MUST be > 0!!! |
| * This is done for performance reasons, so no initial check has do be done. |
| * |
| * Return value |
| * 1: Data has been copied |
| * 0: No space, data has not been copied |
| * |
| * Notes |
| * (1) If there is not enough space in the "Up"-buffer, all data is dropped. |
| * (2) For performance reasons this function does not call Init() |
| * and may only be called after RTT has been initialized. |
| * Either by calling SEGGER_RTT_Init() or calling another RTT API function first. |
| */ |
| _SECTION(.text, CODE, 2) |
| _ALIGN(2) |
| _THUMB_FUNC |
| SEGGER_RTT_ASM_WriteSkipNoLock: // unsigned SEGGER_RTT_WriteSkipNoLock(unsigned BufferIndex, const void* pData, unsigned NumBytes) { |
| // |
| // Cases: |
| // 1) RdOff <= WrOff => Space until wrap-around is sufficient |
| // 2) RdOff <= WrOff => Space after wrap-around needed (copy in 2 chunks) |
| // 3) RdOff < WrOff => No space in buf |
| // 4) RdOff > WrOff => Space is sufficient |
| // 5) RdOff > WrOff => No space in buf |
| // |
| // 1) is the most common case for large buffers and assuming that J-Link reads the data fast enough |
| // |
| // Register usage: |
| // R0 Temporary needed as RdOff, <Tmp> register later on |
| // R1 pData |
| // R2 <NumBytes> |
| // R3 <Tmp> register. Hold free for subroutine calls |
| // R4 <Rem> |
| // R5 pRing->pBuffer |
| // R6 pRing (Points to active struct SEGGER_RTT_BUFFER_DOWN) |
| // R7 WrOff |
| // |
| PUSH {R4-R7} |
| ADD R3,R0,R0, LSL #+1 |
| LDR.W R0,=_SEGGER_RTT // pRing = &_SEGGER_RTT.aUp[BufferIndex]; |
| ADD R0,R0,R3, LSL #+3 |
| ADD R6,R0,#+24 |
| LDR R0,[R6, #+16] // RdOff = pRing->RdOff; |
| LDR R7,[R6, #+12] // WrOff = pRing->WrOff; |
| LDR R5,[R6, #+4] // pRing->pBuffer |
| CMP R7,R0 |
| BCC.N _CheckCase4 // if (RdOff <= WrOff) { => Case 1), 2) or 3) |
| // |
| // Handling for case 1, later on identical to case 4 |
| // |
| LDR R3,[R6, #+8] // Avail = pRing->SizeOfBuffer - WrOff - 1u; => Space until wrap-around (assume 1 byte not usable for case that RdOff == 0) |
| SUBS R4,R3,R7 // <Rem> (Used in case we jump into case 2 afterwards) |
| SUBS R3,R4,#+1 // <Avail> |
| CMP R3,R2 |
| BCC.N _CheckCase2 // if (Avail >= NumBytes) { => Case 1)? |
| _Case4: |
| ADDS R5,R7,R5 // pBuffer += WrOff |
| ADDS R0,R2,R7 // v = WrOff + NumBytes |
| // |
| // 2x unrolling for the copy loop that is used most of the time |
| // This is a special optimization for small SystemView packets and makes them even faster |
| // |
| _ALIGN(2) |
| _LoopCopyStraight: // memcpy(pRing->pBuffer + WrOff, pData, NumBytes); |
| LDRB R3,[R1], #+1 |
| STRB R3,[R5], #+1 // *pDest++ = *pSrc++ |
| SUBS R2,R2,#+1 |
| BEQ _CSDone |
| LDRB R3,[R1], #+1 |
| STRB R3,[R5], #+1 // *pDest++ = *pSrc++ |
| SUBS R2,R2,#+1 |
| BNE _LoopCopyStraight |
| _CSDone: |
| #if _CORE_NEEDS_DMB // Do not slow down cores that do not need a DMB instruction here |
| DMB // Cortex-M7 may delay memory writes and also change the order in which the writes happen. Therefore, make sure that all buffer writes are finished, before updating the <WrOff> in the struct |
| #endif |
| STR R0,[R6, #+12] // pRing->WrOff = WrOff + NumBytes; |
| MOVS R0,#+1 |
| POP {R4-R7} |
| BX LR // Return 1 |
| _CheckCase2: |
| ADDS R0,R0,R3 // Avail += RdOff; => Space incl. wrap-around |
| CMP R0,R2 |
| BCC.N _Case3 // if (Avail >= NumBytes) { => Case 2? => If not, we have case 3) (does not fit) |
| // |
| // Handling for case 2 |
| // |
| ADDS R0,R7,R5 // v = pRing->pBuffer + WrOff => Do not change pRing->pBuffer here because 2nd chunk needs org. value |
| SUBS R2,R2,R4 // NumBytes -= Rem; (Rem = pRing->SizeOfBuffer - WrOff; => Space until end of buffer) |
| _LoopCopyBeforeWrapAround: // memcpy(pRing->pBuffer + WrOff, pData, Rem); => Copy 1st chunk |
| LDRB R3,[R1], #+1 |
| STRB R3,[R0], #+1 // *pDest++ = *pSrc++ |
| SUBS R4,R4,#+1 |
| BNE _LoopCopyBeforeWrapAround |
| // |
| // Special case: First check that assumed RdOff == 0 calculated that last element before wrap-around could not be used |
| // But 2nd check (considering space until wrap-around and until RdOff) revealed that RdOff is not 0, so we can use the last element |
| // In this case, we may use a copy straight until buffer end anyway without needing to copy 2 chunks |
| // Therefore, check if 2nd memcpy is necessary at all |
| // |
| ADDS R4,R2,#+0 // Save <NumBytes> (needed as counter in loop but must be written to <WrOff> after the loop). Also use this inst to update the flags to skip 2nd loop if possible |
| BEQ.N _No2ChunkNeeded // if (NumBytes) { |
| _LoopCopyAfterWrapAround: // memcpy(pRing->pBuffer, pData + Rem, NumBytes); |
| LDRB R3,[R1], #+1 // pData already points to the next src byte due to copy loop increment before this loop |
| STRB R3,[R5], #+1 // *pDest++ = *pSrc++ |
| SUBS R2,R2,#+1 |
| BNE _LoopCopyAfterWrapAround |
| _No2ChunkNeeded: |
| #if _CORE_NEEDS_DMB // Do not slow down cores that do not need a DMB instruction here |
| DMB // Cortex-M7 may delay memory writes and also change the order in which the writes happen. Therefore, make sure that all buffer writes are finished, before updating the <WrOff> in the struct |
| #endif |
| STR R4,[R6, #+12] // pRing->WrOff = NumBytes; => Must be written after copying data because J-Link may read control block asynchronously while writing into buffer |
| MOVS R0,#+1 |
| POP {R4-R7} |
| BX LR // Return 1 |
| _CheckCase4: |
| SUBS R0,R0,R7 |
| SUBS R0,R0,#+1 // Avail = RdOff - WrOff - 1u; |
| CMP R0,R2 |
| BCS.N _Case4 // if (Avail >= NumBytes) { => Case 4) == 1) ? => If not, we have case 5) == 3) (does not fit) |
| _Case3: |
| MOVS R0,#+0 |
| POP {R4-R7} |
| BX LR // Return 0 |
| _PLACE_LITS |
| |
| #endif // defined (RTT_USE_ASM) && (RTT_USE_ASM == 1) |
| _END |
| |
| /*************************** End of file ****************************/ |