/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Context switch support for Hexagon
 *
 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
 */

#include <asm/asm-offsets.h>

.text

/*
 * The register used as a fast-path thread information pointer
 * is determined as a kernel configuration option.  If it happens
 * to be a callee-save register, we're going to be saving and
 * restoring it twice here.
 *
 * This code anticipates a revised ABI where R20-23 are added
 * to the set of callee-save registers, but this should be
 * backward compatible to legacy tools.
 */


/*
 *      void switch_to(struct task_struct *prev,
 *              struct task_struct *next, struct task_struct *last);
 */
        .p2align 2
        .globl __switch_to
        .type   __switch_to, @function

/*
 * When we exit the wormhole, we need to store the previous task
 * in the new R0's pointer.  Technically it should be R2, but they should
 * be the same; seems like a legacy thing.  In short, don't butcher
 * R0, let it go back out unmolested.
 */

__switch_to:
        /*
         * Push callee-saves onto "prev" stack.
         * Here, we're sneaky because the LR and FP
         * storage of the thread_stack structure
         * is automagically allocated by allocframe,
         * so we pass struct size less 8.
         */
        allocframe(#(_SWITCH_STACK_SIZE - 8));
        memd(R29+#(_SWITCH_R2726))=R27:26;
        memd(R29+#(_SWITCH_R2524))=R25:24;
        memd(R29+#(_SWITCH_R2322))=R23:22;
        memd(R29+#(_SWITCH_R2120))=R21:20;
        memd(R29+#(_SWITCH_R1918))=R19:18;
        memd(R29+#(_SWITCH_R1716))=R17:16;
        /* Stash thread_info pointer in task_struct */
        memw(R0+#_TASK_THREAD_INFO) = THREADINFO_REG;
        memw(R0 +#(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)) = R29;
        /* Switch to "next" stack and restore callee saves from there */
        R29 = memw(R1 + #(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP));
        {
            R27:26 = memd(R29+#(_SWITCH_R2726));
            R25:24 = memd(R29+#(_SWITCH_R2524));
        }
        {
            R23:22 = memd(R29+#(_SWITCH_R2322));
            R21:20 = memd(R29+#(_SWITCH_R2120));
        }
        {
            R19:18 = memd(R29+#(_SWITCH_R1918));
            R17:16 = memd(R29+#(_SWITCH_R1716));
        }
        {
            /* THREADINFO_REG is currently one of the callee-saved regs
             * above, and so be sure to re-load it last.
             */
            THREADINFO_REG = memw(R1 + #_TASK_THREAD_INFO);
            R31:30 = memd(R29+#_SWITCH_FP);
        }
        {
            R29 = add(R29,#_SWITCH_STACK_SIZE);
            jumpr R31;
        }
        .size   __switch_to, .-__switch_to