// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * spu_restore.c
 *
 * (C) Copyright IBM Corp. 2005
 *
 * SPU-side context restore sequence outlined in
 * Synergistic Processor Element Book IV
 *
 * Author: Mark Nutter <mnutter@us.ibm.com>
 */


#ifndef LS_SIZE
#define LS_SIZE                 0x40000 /* 256K (in bytes) */
#endif

typedef unsigned int u32;
typedef unsigned long long u64;

#include <spu_intrinsics.h>
#include <asm/spu_csa.h>
#include "spu_utils.h"

#define BR_INSTR                0x327fff80      /* br -4         */
#define NOP_INSTR               0x40200000      /* nop           */
#define HEQ_INSTR               0x7b000000      /* heq $0, $0    */
#define STOP_INSTR              0x00000000      /* stop 0x0      */
#define ILLEGAL_INSTR           0x00800000      /* illegal instr */
#define RESTORE_COMPLETE        0x00003ffc      /* stop 0x3ffc   */

static inline void fetch_regs_from_mem(addr64 lscsa_ea)
{
        unsigned int ls = (unsigned int)&regs_spill[0];
        unsigned int size = sizeof(regs_spill);
        unsigned int tag_id = 0;
        unsigned int cmd = 0x40;        /* GET */

        spu_writech(MFC_LSA, ls);
        spu_writech(MFC_EAH, lscsa_ea.ui[0]);
        spu_writech(MFC_EAL, lscsa_ea.ui[1]);
        spu_writech(MFC_Size, size);
        spu_writech(MFC_TagID, tag_id);
        spu_writech(MFC_Cmd, cmd);
}

static inline void restore_upper_240kb(addr64 lscsa_ea)
{
        unsigned int ls = 16384;
        unsigned int list = (unsigned int)&dma_list[0];
        unsigned int size = sizeof(dma_list);
        unsigned int tag_id = 0;
        unsigned int cmd = 0x44;        /* GETL */

        /* Restore, Step 4:
         *    Enqueue the GETL command (tag 0) to the MFC SPU command
         *    queue to transfer the upper 240 kb of LS from CSA.
         */
        spu_writech(MFC_LSA, ls);
        spu_writech(MFC_EAH, lscsa_ea.ui[0]);
        spu_writech(MFC_EAL, list);
        spu_writech(MFC_Size, size);
        spu_writech(MFC_TagID, tag_id);
        spu_writech(MFC_Cmd, cmd);
}

static inline void restore_decr(void)
{
        unsigned int offset;
        unsigned int decr_running;
        unsigned int decr;

        /* Restore, Step 6(moved):
         *    If the LSCSA "decrementer running" flag is set
         *    then write the SPU_WrDec channel with the
         *    decrementer value from LSCSA.
         */
        offset = LSCSA_QW_OFFSET(decr_status);
        decr_running = regs_spill[offset].slot[0] & SPU_DECR_STATUS_RUNNING;
        if (decr_running) {
                offset = LSCSA_QW_OFFSET(decr);
                decr = regs_spill[offset].slot[0];
                spu_writech(SPU_WrDec, decr);
        }
}

static inline void write_ppu_mb(void)
{
        unsigned int offset;
        unsigned int data;

        /* Restore, Step 11:
         *    Write the MFC_WrOut_MB channel with the PPU_MB
         *    data from LSCSA.
         */
        offset = LSCSA_QW_OFFSET(ppu_mb);
        data = regs_spill[offset].slot[0];
        spu_writech(SPU_WrOutMbox, data);
}

static inline void write_ppuint_mb(void)
{
        unsigned int offset;
        unsigned int data;

        /* Restore, Step 12:
         *    Write the MFC_WrInt_MB channel with the PPUINT_MB
         *    data from LSCSA.
         */
        offset = LSCSA_QW_OFFSET(ppuint_mb);
        data = regs_spill[offset].slot[0];
        spu_writech(SPU_WrOutIntrMbox, data);
}

static inline void restore_fpcr(void)
{
        unsigned int offset;
        vector unsigned int fpcr;

        /* Restore, Step 13:
         *    Restore the floating-point status and control
         *    register from the LSCSA.
         */
        offset = LSCSA_QW_OFFSET(fpcr);
        fpcr = regs_spill[offset].v;
        spu_mtfpscr(fpcr);
}

static inline void restore_srr0(void)
{
        unsigned int offset;
        unsigned int srr0;

        /* Restore, Step 14:
         *    Restore the SPU SRR0 data from the LSCSA.
         */
        offset = LSCSA_QW_OFFSET(srr0);
        srr0 = regs_spill[offset].slot[0];
        spu_writech(SPU_WrSRR0, srr0);
}

static inline void restore_event_mask(void)
{
        unsigned int offset;
        unsigned int event_mask;

        /* Restore, Step 15:
         *    Restore the SPU_RdEventMsk data from the LSCSA.
         */
        offset = LSCSA_QW_OFFSET(event_mask);
        event_mask = regs_spill[offset].slot[0];
        spu_writech(SPU_WrEventMask, event_mask);
}

static inline void restore_tag_mask(void)
{
        unsigned int offset;
        unsigned int tag_mask;

        /* Restore, Step 16:
         *    Restore the SPU_RdTagMsk data from the LSCSA.
         */
        offset = LSCSA_QW_OFFSET(tag_mask);
        tag_mask = regs_spill[offset].slot[0];
        spu_writech(MFC_WrTagMask, tag_mask);
}

static inline void restore_complete(void)
{
        extern void exit_fini(void);
        unsigned int *exit_instrs = (unsigned int *)exit_fini;
        unsigned int offset;
        unsigned int stopped_status;
        unsigned int stopped_code;

        /* Restore, Step 18:
         *    Issue a stop-and-signal instruction with
         *    "good context restore" signal value.
         *
         * Restore, Step 19:
         *    There may be additional instructions placed
         *    here by the PPE Sequence for SPU Context
         *    Restore in order to restore the correct
         *    "stopped state".
         *
         *    This step is handled here by analyzing the
         *    LSCSA.stopped_status and then modifying the
         *    exit() function to behave appropriately.
         */

        offset = LSCSA_QW_OFFSET(stopped_status);
        stopped_status = regs_spill[offset].slot[0];
        stopped_code = regs_spill[offset].slot[1];

        switch (stopped_status) {
        case SPU_STOPPED_STATUS_P_I:
                /* SPU_Status[P,I]=1.  Add illegal instruction
                 * followed by stop-and-signal instruction after
                 * end of restore code.
                 */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = ILLEGAL_INSTR;
                exit_instrs[2] = STOP_INSTR | stopped_code;
                break;
        case SPU_STOPPED_STATUS_P_H:
                /* SPU_Status[P,H]=1.  Add 'heq $0, $0' followed
                 * by stop-and-signal instruction after end of
                 * restore code.
                 */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = HEQ_INSTR;
                exit_instrs[2] = STOP_INSTR | stopped_code;
                break;
        case SPU_STOPPED_STATUS_S_P:
                /* SPU_Status[S,P]=1.  Add nop instruction
                 * followed by 'br -4' after end of restore
                 * code.
                 */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = STOP_INSTR | stopped_code;
                exit_instrs[2] = NOP_INSTR;
                exit_instrs[3] = BR_INSTR;
                break;
        case SPU_STOPPED_STATUS_S_I:
                /* SPU_Status[S,I]=1.  Add  illegal instruction
                 * followed by 'br -4' after end of restore code.
                 */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = ILLEGAL_INSTR;
                exit_instrs[2] = NOP_INSTR;
                exit_instrs[3] = BR_INSTR;
                break;
        case SPU_STOPPED_STATUS_I:
                /* SPU_Status[I]=1. Add illegal instruction followed
                 * by infinite loop after end of restore sequence.
                 */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = ILLEGAL_INSTR;
                exit_instrs[2] = NOP_INSTR;
                exit_instrs[3] = BR_INSTR;
                break;
        case SPU_STOPPED_STATUS_S:
                /* SPU_Status[S]=1. Add two 'nop' instructions. */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = NOP_INSTR;
                exit_instrs[2] = NOP_INSTR;
                exit_instrs[3] = BR_INSTR;
                break;
        case SPU_STOPPED_STATUS_H:
                /* SPU_Status[H]=1. Add 'heq $0, $0' instruction
                 * after end of restore code.
                 */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = HEQ_INSTR;
                exit_instrs[2] = NOP_INSTR;
                exit_instrs[3] = BR_INSTR;
                break;
        case SPU_STOPPED_STATUS_P:
                /* SPU_Status[P]=1. Add stop-and-signal instruction
                 * after end of restore code.
                 */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = STOP_INSTR | stopped_code;
                break;
        case SPU_STOPPED_STATUS_R:
                /* SPU_Status[I,S,H,P,R]=0. Add infinite loop. */
                exit_instrs[0] = RESTORE_COMPLETE;
                exit_instrs[1] = NOP_INSTR;
                exit_instrs[2] = NOP_INSTR;
                exit_instrs[3] = BR_INSTR;
                break;
        default:
                /* SPU_Status[R]=1. No additional instructions. */
                break;
        }
        spu_sync();
}

/**
 * main - entry point for SPU-side context restore.
 *
 * This code deviates from the documented sequence in the
 * following aspects:
 *
 *      1. The EA for LSCSA is passed from PPE in the
 *         signal notification channels.
 *      2. The register spill area is pulled by SPU
 *         into LS, rather than pushed by PPE.
 *      3. All 128 registers are restored by exit().
 *      4. The exit() function is modified at run
 *         time in order to properly restore the
 *         SPU_Status register.
 */
int main()
{
        addr64 lscsa_ea;

        lscsa_ea.ui[0] = spu_readch(SPU_RdSigNotify1);
        lscsa_ea.ui[1] = spu_readch(SPU_RdSigNotify2);
        fetch_regs_from_mem(lscsa_ea);

        set_event_mask();               /* Step 1.  */
        set_tag_mask();                 /* Step 2.  */
        build_dma_list(lscsa_ea);       /* Step 3.  */
        restore_upper_240kb(lscsa_ea);  /* Step 4.  */
                                        /* Step 5: done by 'exit'. */
        enqueue_putllc(lscsa_ea);       /* Step 7. */
        set_tag_update();               /* Step 8. */
        read_tag_status();              /* Step 9. */
        restore_decr();                 /* moved Step 6. */
        read_llar_status();             /* Step 10. */
        write_ppu_mb();                 /* Step 11. */
        write_ppuint_mb();              /* Step 12. */
        restore_fpcr();                 /* Step 13. */
        restore_srr0();                 /* Step 14. */
        restore_event_mask();           /* Step 15. */
        restore_tag_mask();             /* Step 16. */
                                        /* Step 17. done by 'exit'. */
        restore_complete();             /* Step 18. */

        return 0;
}