/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (C) 1996 Wolfgang Solfrank.
 * Copyright (C) 1996 TooLs GmbH.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by TooLs GmbH.
 * 4. The name of TooLs GmbH may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *      $NetBSD: fpu.c,v 1.5 2001/07/22 11:29:46 wiz Exp $
 */

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/limits.h>

#include <machine/fpu.h>
#include <machine/pcb.h>
#include <machine/psl.h>
#include <machine/altivec.h>

static void
save_fpu_int(struct thread *td)
{
        register_t msr;
        struct  pcb *pcb;

        pcb = td->td_pcb;

        /*
         * Temporarily re-enable floating-point during the save
         */
        msr = mfmsr();
        if (pcb->pcb_flags & PCB_VSX)
                mtmsr(msr | PSL_FP | PSL_VSX);
        else
                mtmsr(msr | PSL_FP);

        /*
         * Save the floating-point registers and FPSCR to the PCB
         */
        if (pcb->pcb_flags & PCB_VSX) {
#if _BYTE_ORDER == _BIG_ENDIAN
        #define SFP(n)   __asm("stxvw4x " #n ", 0,%0" \
                        :: "b"(&pcb->pcb_fpu.fpr[n]));
#else
        /*
         * stxvw2x will swap words within the FP double word on LE systems,
         * leading to corruption if VSX is used to store state and FP is
         * subsequently used to restore state.
         * Use stxvd2x instead.
         */
        #define SFP(n)   __asm("stxvd2x " #n ", 0,%0" \
                        :: "b"(&pcb->pcb_fpu.fpr[n]));
#endif
                SFP(0);         SFP(1);         SFP(2);         SFP(3);
                SFP(4);         SFP(5);         SFP(6);         SFP(7);
                SFP(8);         SFP(9);         SFP(10);        SFP(11);
                SFP(12);        SFP(13);        SFP(14);        SFP(15);
                SFP(16);        SFP(17);        SFP(18);        SFP(19);
                SFP(20);        SFP(21);        SFP(22);        SFP(23);
                SFP(24);        SFP(25);        SFP(26);        SFP(27);
                SFP(28);        SFP(29);        SFP(30);        SFP(31);
        #undef SFP
        } else {
        #define SFP(n)   __asm("stfd " #n ", 0(%0)" \
                        :: "b"(&pcb->pcb_fpu.fpr[n].fpr));
                SFP(0);         SFP(1);         SFP(2);         SFP(3);
                SFP(4);         SFP(5);         SFP(6);         SFP(7);
                SFP(8);         SFP(9);         SFP(10);        SFP(11);
                SFP(12);        SFP(13);        SFP(14);        SFP(15);
                SFP(16);        SFP(17);        SFP(18);        SFP(19);
                SFP(20);        SFP(21);        SFP(22);        SFP(23);
                SFP(24);        SFP(25);        SFP(26);        SFP(27);
                SFP(28);        SFP(29);        SFP(30);        SFP(31);
        #undef SFP
        }
        __asm __volatile ("mffs 0; stfd 0,0(%0)" :: "b"(&pcb->pcb_fpu.fpscr));

        /*
         * Disable floating-point again
         */
        isync();
        mtmsr(msr);
}

void
enable_fpu(struct thread *td)
{
        register_t msr;
        struct  pcb *pcb;
        struct  trapframe *tf;

        pcb = td->td_pcb;
        tf = trapframe(td);

        /*
         * Save the thread's FPU CPU number, and set the CPU's current
         * FPU thread
         */
        td->td_pcb->pcb_fpcpu = PCPU_GET(cpuid);
        PCPU_SET(fputhread, td);

        /*
         * Enable the FPU for when the thread returns from the exception.
         * If this is the first time the FPU has been used by the thread,
         * initialise the FPU registers and FPSCR to 0, and set the flag
         * to indicate that the FPU is in use.
         */
        pcb->pcb_flags |= PCB_FPU;
        if (pcb->pcb_flags & PCB_VSX)
                tf->srr1 |= PSL_FP | PSL_VSX;
        else
                tf->srr1 |= PSL_FP;
        if (!(pcb->pcb_flags & PCB_FPREGS)) {
                memset(&pcb->pcb_fpu, 0, sizeof pcb->pcb_fpu);
                pcb->pcb_flags |= PCB_FPREGS;
        }

        /*
         * Temporarily enable floating-point so the registers
         * can be restored.
         */
        msr = mfmsr();
        if (pcb->pcb_flags & PCB_VSX)
                mtmsr(msr | PSL_FP | PSL_VSX);
        else
                mtmsr(msr | PSL_FP);

        /*
         * Load the floating point registers and FPSCR from the PCB.
         * (A value of 0xff for mtfsf specifies that all 8 4-bit fields
         * of the saved FPSCR are to be loaded from the FPU reg).
         */
        __asm __volatile ("lfd 0,0(%0); mtfsf 0xff,0"
                          :: "b"(&pcb->pcb_fpu.fpscr));

        if (pcb->pcb_flags & PCB_VSX) {
#if _BYTE_ORDER == _BIG_ENDIAN
        #define LFP(n)   __asm("lxvw4x " #n ", 0,%0" \
                        :: "b"(&pcb->pcb_fpu.fpr[n]));
#else
        /*
         * lxvw4x will swap words within the FP double word on LE systems,
         * leading to corruption if FP is used to store state and VSX is
         * subsequently used to restore state.
         * Use lxvd2x instead.
         */
        #define LFP(n)   __asm("lxvd2x " #n ", 0,%0" \
                        :: "b"(&pcb->pcb_fpu.fpr[n]));
#endif
                LFP(0);         LFP(1);         LFP(2);         LFP(3);
                LFP(4);         LFP(5);         LFP(6);         LFP(7);
                LFP(8);         LFP(9);         LFP(10);        LFP(11);
                LFP(12);        LFP(13);        LFP(14);        LFP(15);
                LFP(16);        LFP(17);        LFP(18);        LFP(19);
                LFP(20);        LFP(21);        LFP(22);        LFP(23);
                LFP(24);        LFP(25);        LFP(26);        LFP(27);
                LFP(28);        LFP(29);        LFP(30);        LFP(31);
        #undef LFP
        } else {
        #define LFP(n)   __asm("lfd " #n ", 0(%0)" \
                        :: "b"(&pcb->pcb_fpu.fpr[n].fpr));
                LFP(0);         LFP(1);         LFP(2);         LFP(3);
                LFP(4);         LFP(5);         LFP(6);         LFP(7);
                LFP(8);         LFP(9);         LFP(10);        LFP(11);
                LFP(12);        LFP(13);        LFP(14);        LFP(15);
                LFP(16);        LFP(17);        LFP(18);        LFP(19);
                LFP(20);        LFP(21);        LFP(22);        LFP(23);
                LFP(24);        LFP(25);        LFP(26);        LFP(27);
                LFP(28);        LFP(29);        LFP(30);        LFP(31);
        #undef LFP
        }

        isync();
        mtmsr(msr);
}

void
save_fpu(struct thread *td)
{
        struct  pcb *pcb;

        pcb = td->td_pcb;

        save_fpu_int(td);

        /*
         * Clear the current fp thread and pcb's CPU id
         * XXX should this be left clear to allow lazy save/restore ?
         */
        pcb->pcb_fpcpu = INT_MAX;
        PCPU_SET(fputhread, NULL);
}

/*
 * Save fpu state without dropping ownership.  This will only save state if
 * the current fpu thread is `td'.
 */
void
save_fpu_nodrop(struct thread *td)
{

        if (td == PCPU_GET(fputhread))
                save_fpu_int(td);
}

/*
 * Clear Floating-Point Status and Control Register
 */
void
cleanup_fpscr(void)
{
        register_t msr;

        msr = mfmsr();
        mtmsr(msr | PSL_FP);
        mtfsf(0);

        isync();
        mtmsr(msr);
}

/*
 * Get the current fp exception
 */
u_int
get_fpu_exception(struct thread *td)
{
        register_t msr;
        u_int ucode;
        register_t reg;

        critical_enter();

        msr = mfmsr();
        mtmsr(msr | PSL_FP);

        reg = mffs();

        isync();
        mtmsr(msr);

        critical_exit();

        if (reg & FPSCR_ZX)
                ucode = FPE_FLTDIV;
        else if (reg & FPSCR_OX)
                ucode = FPE_FLTOVF;
        else if (reg & FPSCR_UX)
                ucode = FPE_FLTUND;
        else if (reg & FPSCR_XX)
                ucode = FPE_FLTRES;
        else
                ucode = FPE_FLTINV;

        return ucode;
}

void
enable_fpu_kern(void)
{
        register_t msr;

        msr = mfmsr() | PSL_FP;

        if (cpu_features & PPC_FEATURE_HAS_VSX)
                msr |= PSL_VSX;

        mtmsr(msr);
}

void
disable_fpu(struct thread *td)
{
        register_t msr;
        struct pcb *pcb;
        struct trapframe *tf;

        pcb = td->td_pcb;
        tf = trapframe(td);

        /* Disable FPU in kernel (if enabled) */
        msr = mfmsr() & ~(PSL_FP | PSL_VSX);
        isync();
        mtmsr(msr);

        /*
         * Disable FPU in userspace. It will be re-enabled when
         * an FP or VSX instruction is executed.
         */
        tf->srr1 &= ~(PSL_FP | PSL_VSX);
        pcb->pcb_flags &= ~(PCB_FPU | PCB_VSX);
}

/*
 * XXX: Implement fpu_kern_alloc_ctx/fpu_kern_free_ctx once fpu_kern_enter and
 * fpu_kern_leave can handle !FPU_KERN_NOCTX.
 */
struct fpu_kern_ctx {
#define FPU_KERN_CTX_DUMMY      0x01    /* avoided save for the kern thread */
#define FPU_KERN_CTX_INUSE      0x02
        uint32_t         flags;
};

void
fpu_kern_enter(struct thread *td, struct fpu_kern_ctx *ctx, u_int flags)
{
        struct pcb *pcb;

        pcb = td->td_pcb;

        KASSERT((flags & FPU_KERN_NOCTX) != 0 || ctx != NULL,
            ("ctx is required when !FPU_KERN_NOCTX"));
        KASSERT(ctx == NULL || (ctx->flags & FPU_KERN_CTX_INUSE) == 0,
            ("using inuse ctx"));
        KASSERT((pcb->pcb_flags & PCB_KERN_FPU_NOSAVE) == 0,
            ("recursive fpu_kern_enter while in PCB_KERN_FPU_NOSAVE state"));

        if ((flags & FPU_KERN_NOCTX) != 0) {
                critical_enter();

                if (pcb->pcb_flags & PCB_FPU) {
                        save_fpu(td);
                        pcb->pcb_flags |= PCB_FPREGS;
                }
                enable_fpu_kern();

                if (pcb->pcb_flags & PCB_VEC) {
                        save_vec(td);
                        pcb->pcb_flags |= PCB_VECREGS;
                }
                enable_vec_kern();

                pcb->pcb_flags |= PCB_KERN_FPU | PCB_KERN_FPU_NOSAVE;
                return;
        }

        KASSERT(0, ("fpu_kern_enter with !FPU_KERN_NOCTX not implemented!"));
}

int
fpu_kern_leave(struct thread *td, struct fpu_kern_ctx *ctx)
{
        struct pcb *pcb;

        pcb = td->td_pcb;

        if ((pcb->pcb_flags & PCB_KERN_FPU_NOSAVE) != 0) {
                KASSERT(ctx == NULL, ("non-null ctx after FPU_KERN_NOCTX"));
                KASSERT(PCPU_GET(fpcurthread) == NULL,
                    ("non-NULL fpcurthread for PCB_FP_NOSAVE"));
                CRITICAL_ASSERT(td);

                /* Disable FPU, VMX, and VSX */
                disable_fpu(td);
                disable_vec(td);

                pcb->pcb_flags &= ~PCB_KERN_FPU_NOSAVE;

                critical_exit();
        } else {
                KASSERT(0, ("fpu_kern_leave with !FPU_KERN_NOCTX not implemented!"));
        }

        pcb->pcb_flags &= ~PCB_KERN_FPU;

        return 0;
}

int
is_fpu_kern_thread(u_int flags __unused)
{
        struct pcb *curpcb;

        if ((curthread->td_pflags & TDP_KTHREAD) == 0)
                return (0);
        curpcb = curthread->td_pcb;
        return ((curpcb->pcb_flags & PCB_KERN_FPU) != 0);
}