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