/* * Copyright (c) 2016 Cadence Design Systems, Inc. * SPDX-License-Identifier: Apache-2.0 */ /* * XTENSA CONTEXT FRAMES AND MACROS FOR RTOS ASSEMBLER SOURCES * * This header contains definitions and macros for use primarily by Xtensa RTOS * assembly coded source files. It includes and uses the Xtensa hardware * abstraction layer (HAL) to deal with config specifics. It may also be * included in C source files. * * Supports only Xtensa Exception Architecture 2 (XEA2). XEA1 not supported. * * NOTE: The Xtensa architecture requires stack pointer alignment to 16 bytes. */ #ifndef XTENSA_CONTEXT_H #define XTENSA_CONTEXT_H #ifdef __ASSEMBLER__ #include #endif #include #include #include #include /* Align a value up to nearest n-byte boundary, where n is a power of 2. */ #define ALIGNUP(n, val) (((val) + (n)-1) & -(n)) /* * INTERRUPT/EXCEPTION STACK FRAME FOR A THREAD OR NESTED INTERRUPT * * A stack frame of this structure is allocated for any interrupt or exception. * It goes on the current stack. If the RTOS has a system stack for handling * interrupts, every thread stack must allow space for just one interrupt stack * frame, then nested interrupt stack frames go on the system stack. * * The frame includes basic registers (explicit) and "extra" registers * introduced by user TIE or the use of the MAC16 option in the user's Xtensa * config. The frame size is minimized by omitting regs not applicable to * user's config. * * For Windowed ABI, this stack frame includes the interruptee's base save * area, another base save area to manage gcc nested functions, and a little * temporary space to help manage the spilling of the register windows. */ STRUCT_BEGIN STRUCT_FIELD(long, 4, XT_STK_, exit) /* exit point for dispatch */ STRUCT_FIELD(long, 4, XT_STK_, pc) /* return PC */ STRUCT_FIELD(long, 4, XT_STK_, ps) /* return PS */ STRUCT_FIELD(long, 4, XT_STK_, a0) STRUCT_FIELD(long, 4, XT_STK_, a1) /* stack pointer before irq */ STRUCT_FIELD(long, 4, XT_STK_, a2) STRUCT_FIELD(long, 4, XT_STK_, a3) STRUCT_FIELD(long, 4, XT_STK_, a4) STRUCT_FIELD(long, 4, XT_STK_, a5) STRUCT_FIELD(long, 4, XT_STK_, a6) STRUCT_FIELD(long, 4, XT_STK_, a7) STRUCT_FIELD(long, 4, XT_STK_, a8) STRUCT_FIELD(long, 4, XT_STK_, a9) STRUCT_FIELD(long, 4, XT_STK_, a10) STRUCT_FIELD(long, 4, XT_STK_, a11) STRUCT_FIELD(long, 4, XT_STK_, a12) STRUCT_FIELD(long, 4, XT_STK_, a13) STRUCT_FIELD(long, 4, XT_STK_, a14) STRUCT_FIELD(long, 4, XT_STK_, a15) STRUCT_FIELD(long, 4, XT_STK_, sar) STRUCT_FIELD(long, 4, XT_STK_, exccause) STRUCT_FIELD(long, 4, XT_STK_, excvaddr) #if XCHAL_HAVE_LOOPS STRUCT_FIELD(long, 4, XT_STK_, lbeg) STRUCT_FIELD(long, 4, XT_STK_, lend) STRUCT_FIELD(long, 4, XT_STK_, lcount) #endif #ifndef __XTENSA_CALL0_ABI__ /* Temporary space for saving stuff during window spill */ STRUCT_FIELD(long, 4, XT_STK_, tmp0) STRUCT_FIELD(long, 4, XT_STK_, tmp1) STRUCT_FIELD(long, 4, XT_STK_, tmp2) #endif #ifdef XT_USE_SWPRI /* Storage for virtual priority mask */ STRUCT_FIELD(long, 4, XT_STK_, vpri) #endif #ifdef XT_USE_OVLY /* Storage for overlay state */ STRUCT_FIELD(long, 4, XT_STK_, ovly) #endif STRUCT_END(XtExcFrame) #if defined(_ASMLANGUAGE) || defined(__ASSEMBLER__) #define XT_STK_NEXT1 XtExcFrameSize #else #define XT_STK_NEXT1 sizeof(XtExcFrame) #endif /* Allocate extra storage if needed */ #if XCHAL_EXTRA_SA_SIZE != 0 #if XCHAL_EXTRA_SA_ALIGN <= 16 #define XT_STK_EXTRA ALIGNUP(XCHAL_EXTRA_SA_ALIGN, XT_STK_NEXT1) #else /* If need more alignment than stack, add space for dynamic alignment */ #define XT_STK_EXTRA (ALIGNUP(XCHAL_EXTRA_SA_ALIGN, XT_STK_NEXT1) \ + XCHAL_EXTRA_SA_ALIGN) #endif #define XT_STK_NEXT2 (XT_STK_EXTRA + XCHAL_EXTRA_SA_SIZE) #else #define XT_STK_NEXT2 XT_STK_NEXT1 #endif /* * This is the frame size. Add space for 4 registers (interruptee's base save * area) and some space for gcc nested functions if any. */ #define XT_STK_FRMSZ (ALIGNUP(0x10, XT_STK_NEXT2) + 0x20) /* * SOLICITED STACK FRAME FOR A THREAD * * A stack frame of this structure is allocated whenever a thread enters the * RTOS kernel intentionally (and synchronously) to submit to thread * scheduling. It goes on the current thread's stack. * * The solicited frame only includes registers that are required to be * preserved by the callee according to the compiler's ABI conventions, some * space to save the return address for returning to the caller, and the * caller's PS register. For Windowed ABI, this stack frame includes the * caller's base save area. * * Note on XT_SOL_EXIT field: * * It is necessary to distinguish a solicited from an interrupt stack frame. * This field corresponds to XT_STK_EXIT in the interrupt stack frame and is * always at the same offset (0). It can be written with a code (usually 0) to * distinguish a solicted frame from an interrupt frame. An RTOS port may opt * to ignore this field if it has another way of distinguishing frames. */ STRUCT_BEGIN STRUCT_FIELD(long, 4, XT_SOL_, exit) STRUCT_FIELD(long, 4, XT_SOL_, pc) STRUCT_FIELD(long, 4, XT_SOL_, ps) STRUCT_FIELD(long, 4, XT_SOL_, next) #ifdef __XTENSA_CALL0_ABI__ STRUCT_FIELD(long, 4, XT_SOL_, a12) /* should be on 16-byte alignment */ STRUCT_FIELD(long, 4, XT_SOL_, a13) STRUCT_FIELD(long, 4, XT_SOL_, a14) STRUCT_FIELD(long, 4, XT_SOL_, a15) #else STRUCT_FIELD(long, 4, XT_SOL_, a0) /* should be on 16-byte alignment */ STRUCT_FIELD(long, 4, XT_SOL_, a1) STRUCT_FIELD(long, 4, XT_SOL_, a2) STRUCT_FIELD(long, 4, XT_SOL_, a3) #endif STRUCT_END(XtSolFrame) /* Size of solicited stack frame */ #define XT_SOL_FRMSZ ALIGNUP(0x10, XtSolFrameSize) /* * CO-PROCESSOR STATE SAVE AREA FOR A THREAD * * The RTOS must provide an area per thread to save the state of co-processors * when that thread does not have control. Co-processors are context-switched * lazily (on demand) only when a new thread uses a co-processor instruction, * otherwise a thread retains ownership of the co-processor even when it loses * control of the processor. An Xtensa co-processor exception is triggered when * any co-processor instruction is executed by a thread that is not the owner, * and the context switch of that co-processor is then peformed by the handler. * Ownership represents which thread's state is currently in the co-processor. * * Co-processors may not be used by interrupt or exception handlers. If a * co-processor instruction is executed by an interrupt or exception handler, * the co-processor exception handler will trigger a kernel panic and freeze. * This restriction is introduced to reduce the overhead of saving and * restoring co-processor state (which can be quite large) and in particular * remove that overhead from interrupt handlers. * * The co-processor state save area may be in any convenient per-thread * location such as in the thread control block or above the thread stack area. * It need not be in the interrupt stack frame since interrupts don't use * co-processors. * * Along with the save area for each co-processor, two bitmasks with flags per * co-processor (laid out as in the CPENABLE reg) help manage context-switching * co-processors as efficiently as possible: * * XT_CPENABLE * * The contents of a non-running thread's CPENABLE register. It represents the * co-processors owned (and whose state is still needed) by the thread. When a * thread is preempted, its CPENABLE is saved here. When a thread solicits a * context-swtich, its CPENABLE is cleared - the compiler has saved the * (caller-saved) co-proc state if it needs to. When a non-running thread * loses ownership of a CP, its bit is cleared. When a thread runs, it's * XT_CPENABLE is loaded into the CPENABLE reg. Avoids co-processor exceptions * when no change of ownership is needed. * * XT_CPSTORED * * A bitmask with the same layout as CPENABLE, a bit per co-processor. * Indicates whether the state of each co-processor is saved in the state save * area. When a thread enters the kernel, only the state of co-procs still * enabled in CPENABLE is saved. When the co-processor exception handler * assigns ownership of a co-processor to a thread, it restores the saved state * only if this bit is set, and clears this bit. * * XT_CP_CS_ST * * A bitmask with the same layout as CPENABLE, a bit per co-processor. * Indicates whether callee-saved state is saved in the state save area. * Callee-saved state is saved by itself on a solicited context switch, and * restored when needed by the coprocessor exception handler. Unsolicited * switches will cause the entire coprocessor to be saved when necessary. * * XT_CP_ASA * * Pointer to the aligned save area. Allows it to be aligned more than the * overall save area (which might only be stack-aligned or TCB-aligned). * Especially relevant for Xtensa cores configured with a very large data path * that requires alignment greater than 16 bytes (ABI stack alignment). */ #define XT_CP_DESCR_SIZE 12 #if XCHAL_CP_NUM > 0 /* Offsets of each coprocessor save area within the 'aligned save area': */ #define XT_CP0_SA 0 #define XT_CP1_SA ALIGNUP(XCHAL_CP1_SA_ALIGN, XT_CP0_SA + XCHAL_CP0_SA_SIZE) #define XT_CP2_SA ALIGNUP(XCHAL_CP2_SA_ALIGN, XT_CP1_SA + XCHAL_CP1_SA_SIZE) #define XT_CP3_SA ALIGNUP(XCHAL_CP3_SA_ALIGN, XT_CP2_SA + XCHAL_CP2_SA_SIZE) #define XT_CP4_SA ALIGNUP(XCHAL_CP4_SA_ALIGN, XT_CP3_SA + XCHAL_CP3_SA_SIZE) #define XT_CP5_SA ALIGNUP(XCHAL_CP5_SA_ALIGN, XT_CP4_SA + XCHAL_CP4_SA_SIZE) #define XT_CP6_SA ALIGNUP(XCHAL_CP6_SA_ALIGN, XT_CP5_SA + XCHAL_CP5_SA_SIZE) #define XT_CP7_SA ALIGNUP(XCHAL_CP7_SA_ALIGN, XT_CP6_SA + XCHAL_CP6_SA_SIZE) #define XT_CP_SA_SIZE ALIGNUP(16, XT_CP7_SA + XCHAL_CP7_SA_SIZE) /* Offsets within the overall save area: */ /* (2 bytes) coprocessors active for this thread */ #define XT_CPENABLE 0 /* (2 bytes) coprocessors saved for this thread */ #define XT_CPSTORED 2 /* (2 bytes) coprocessor callee-saved regs stored for this thread */ #define XT_CP_CS_ST 4 /* (4 bytes) ptr to aligned save area */ #define XT_CP_ASA 8 /* Overall size allows for dynamic alignment: */ #define XT_CP_SIZE ALIGNUP(XCHAL_TOTAL_SA_ALIGN, \ XT_CP_DESCR_SIZE + XT_CP_SA_SIZE) #else #define XT_CP_SIZE 0 #endif /* * MACROS TO HANDLE ABI SPECIFICS OF FUNCTION ENTRY AND RETURN * * Convenient where the frame size requirements are the same for both ABIs. * ENTRY(sz), RET(sz) are for framed functions (have locals or make calls). * ENTRY0, RET0 are for frameless functions (no locals, no calls). * * where size = size of stack frame in bytes (must be >0 and aligned to 16). * For framed functions the frame is created and the return address saved at * base of frame (Call0 ABI) or as determined by hardware (Windowed ABI). For * frameless functions, there is no frame and return address remains in * a0. * * Note: Because CPP macros expand to a single line, macros requiring * multi-line expansions are implemented as assembler macros. */ #ifdef __ASSEMBLER__ #ifdef __XTENSA_CALL0_ABI__ /* Call0 */ #define ENTRY(sz) entry1 sz .macro entry1 size=0x10 addi sp, sp, -\size s32i a0, sp, 0 .endm #define ENTRY0 #define RET(sz) ret1 sz .macro ret1 size=0x10 l32i a0, sp, 0 addi sp, sp, \size ret .endm #define RET0 ret #else /* Windowed */ #define ENTRY(sz) entry sp, sz #define ENTRY0 entry sp, 0x10 #define RET(sz) retw #define RET0 retw #endif /* __XTENSA_CALL0_ABI__ */ #endif /* __ASSEMBLER__ */ #endif /* XTENSA_CONTEXT_H */