/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright (C) 2001,2002,2003 Broadcom Corporation
 */

#include <asm/asm.h>
#include <asm/regdef.h>
#include <asm/mipsregs.h>
#include <asm/stackframe.h>
#include <asm/cacheops.h>
#include <asm/sibyte/board.h>

#define C0_ERRCTL     $26             /* CP0: Error info */
#define C0_CERR_I     $27             /* CP0: Icache error */
#define C0_CERR_D     $27,1           /* CP0: Dcache error */

        /*
         * Based on SiByte sample software cache-err/cerr.S
         * CVS revision 1.8.  Only the 'unrecoverable' case
         * is changed.
         */

        .set    mips64
        .set    noreorder
        .set    noat

        /*
         * sb1_cerr_vec: code to be copied to the Cache Error
         * Exception vector.  The code must be pushed out to memory
         * (either by copying to Kseg0 and Kseg1 both, or by flushing
         * the L1 and L2) since it is fetched as 0xa0000100.
         *
         * NOTE: Be sure this handler is at most 28 instructions long
         * since the final 16 bytes of the exception vector memory
         * (0x170-0x17f) are used to preserve k0, k1, and ra.
         */

LEAF(except_vec2_sb1)
        /*
         * If this error is recoverable, we need to exit the handler
         * without having dirtied any registers.  To do this,
         * save/restore k0 and k1 from low memory (Useg is direct
         * mapped while ERL=1). Note that we can't save to a
         * CPU-specific location without ruining a register in the
         * process.  This means we are vulnerable to data corruption
         * whenever the handler is reentered by a second CPU.
         */
        sd      k0,0x170($0)
        sd      k1,0x178($0)

#ifdef CONFIG_SB1_CEX_ALWAYS_FATAL
        j       handle_vec2_sb1
         nop
#else
        /*
         * M_ERRCTL_RECOVERABLE is bit 31, which makes it easy to tell
         * if we can fast-path out of here for a h/w-recovered error.
         */
        mfc0    k1,C0_ERRCTL
        bgtz    k1,attempt_recovery
         sll    k0,k1,1

recovered_dcache:
        /*
         * Unlock CacheErr-D (which in turn unlocks CacheErr-DPA).
         * Ought to log the occurrence of this recovered dcache error.
         */
        b       recovered
         mtc0   $0,C0_CERR_D

attempt_recovery:
        /*
         * k0 has C0_ERRCTL << 1, which puts 'DC' at bit 31.  Any
         * Dcache errors we can recover from will take more extensive
         * processing.  For now, they are considered "unrecoverable".
         * Note that 'DC' becoming set (outside of ERL mode) will
         * cause 'IC' to clear; so if there's an Icache error, we'll
         * only find out about it if we recover from this error and
         * continue executing.
         */
        bltz    k0,unrecoverable
         sll    k0,1

        /*
         * k0 has C0_ERRCTL << 2, which puts 'IC' at bit 31.  If an
         * Icache error isn't indicated, I'm not sure why we got here.
         * Consider that case "unrecoverable" for now.
         */
        bgez    k0,unrecoverable

attempt_icache_recovery:
        /*
         * External icache errors are due to uncorrectable ECC errors
         * in the L2 cache or Memory Controller and cannot be
         * recovered here.
         */
         mfc0   k0,C0_CERR_I            /* delay slot */
        li      k1,1 << 26              /* ICACHE_EXTERNAL */
        and     k1,k0
        bnez    k1,unrecoverable
         andi   k0,0x1fe0

        /*
         * Since the error is internal, the 'IDX' field from
         * CacheErr-I is valid and we can just invalidate all blocks
         * in that set.
         */
        cache   Index_Invalidate_I,(0<<13)(k0)
        cache   Index_Invalidate_I,(1<<13)(k0)
        cache   Index_Invalidate_I,(2<<13)(k0)
        cache   Index_Invalidate_I,(3<<13)(k0)

        /* Ought to log this recovered icache error */

recovered:
        /* Restore the saved registers */
        ld      k0,0x170($0)
        ld      k1,0x178($0)
        eret

unrecoverable:
        /* Unrecoverable Icache or Dcache error; log it and/or fail */
        j       handle_vec2_sb1
         nop
#endif

END(except_vec2_sb1)

        LEAF(handle_vec2_sb1)
        mfc0    k0,CP0_CONFIG
        li      k1,~CONF_CM_CMASK
        and     k0,k0,k1
        ori     k0,k0,CONF_CM_UNCACHED
        mtc0    k0,CP0_CONFIG

        SSNOP
        SSNOP
        SSNOP
        SSNOP
        bnezl   $0, 1f
1:
        mfc0    k0, CP0_STATUS
        sll     k0, k0, 3                       # check CU0 (kernel?)
        bltz    k0, 2f
         nop

        /* Get a valid Kseg0 stack pointer.  Any task's stack pointer
         * will do, although if we ever want to resume execution we
         * better not have corrupted any state. */
        get_saved_sp
        move    sp, k1

2:
        j       sb1_cache_error
         nop

        END(handle_vec2_sb1)