ecc-berr.c

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/*
 *  Bus error event handling code for systems equipped with ECC
 *  handling logic, i.e. DECstation/DECsystem 5000/200 (KN02),
 *  5000/240 (KN03), 5000/260 (KN05) and DECsystem 5900 (KN03),
 *  5900/260 (KN05) systems.
 *
 *  Copyright (c) 2003, 2005  Maciej W. Rozycki
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/types.h>

#include <asm/addrspace.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
#include <asm/irq_regs.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/traps.h>

#include <asm/dec/ecc.h>
#include <asm/dec/kn02.h>
#include <asm/dec/kn03.h>
#include <asm/dec/kn05.h>

static volatile u32 *kn0x_erraddr;
static volatile u32 *kn0x_chksyn;

static inline void dec_ecc_be_ack(void)
{
    *kn0x_erraddr = 0;          /* any write clears the IRQ */
    iob();
}

static int dec_ecc_be_backend(struct pt_regs *regs, int is_fixup, int invoker)
{
    static const char excstr[] = "exception";
    static const char intstr[] = "interrupt";
    static const char cpustr[] = "CPU";
    static const char dmastr[] = "DMA";
    static const char readstr[] = "read";
    static const char mreadstr[] = "memory read";
    static const char writestr[] = "write";
    static const char mwritstr[] = "partial memory write";
    static const char timestr[] = "timeout";
    static const char overstr[] = "overrun";
    static const char eccstr[] = "ECC error";

    const char *kind, *agent, *cycle, *event;
    const char *status = "", *xbit = "", *fmt = "";
    unsigned long address;
    u16 syn = 0, sngl;

    int i = 0;

    u32 erraddr = *kn0x_erraddr;
    u32 chksyn = *kn0x_chksyn;
    int action = MIPS_BE_FATAL;

    /* For non-ECC ack ASAP, so that any subsequent errors get caught. */
    if ((erraddr & (KN0X_EAR_VALID | KN0X_EAR_ECCERR)) == KN0X_EAR_VALID)
        dec_ecc_be_ack();

    kind = invoker ? intstr : excstr;

    if (!(erraddr & KN0X_EAR_VALID)) {
        /* No idea what happened. */
        printk(KERN_ALERT "Unidentified bus error %s\n", kind);
        return action;
    }

    agent = (erraddr & KN0X_EAR_CPU) ? cpustr : dmastr;

    if (erraddr & KN0X_EAR_ECCERR) {
        /* An ECC error on a CPU or DMA transaction. */
        cycle = (erraddr & KN0X_EAR_WRITE) ? mwritstr : mreadstr;
        event = eccstr;
    } else {
        /* A CPU timeout or a DMA overrun. */
        cycle = (erraddr & KN0X_EAR_WRITE) ? writestr : readstr;
        event = (erraddr & KN0X_EAR_CPU) ? timestr : overstr;
    }

    address = erraddr & KN0X_EAR_ADDRESS;
    /* For ECC errors on reads adjust for MT pipelining. */
    if ((erraddr & (KN0X_EAR_WRITE | KN0X_EAR_ECCERR)) == KN0X_EAR_ECCERR)
        address = (address & ~0xfffLL) | ((address - 5) & 0xfffLL);
    address <<= 2;

    /* Only CPU errors are fixable. */
    if (erraddr & KN0X_EAR_CPU && is_fixup)
        action = MIPS_BE_FIXUP;

    if (erraddr & KN0X_EAR_ECCERR) {
        static const u8 data_sbit[32] = {
            0x4f, 0x4a, 0x52, 0x54, 0x57, 0x58, 0x5b, 0x5d,
            0x23, 0x25, 0x26, 0x29, 0x2a, 0x2c, 0x31, 0x34,
            0x0e, 0x0b, 0x13, 0x15, 0x16, 0x19, 0x1a, 0x1c,
            0x62, 0x64, 0x67, 0x68, 0x6b, 0x6d, 0x70, 0x75,
        };
        static const u8 data_mbit[25] = {
            0x07, 0x0d, 0x1f,
            0x2f, 0x32, 0x37, 0x38, 0x3b, 0x3d, 0x3e,
            0x43, 0x45, 0x46, 0x49, 0x4c, 0x51, 0x5e,
            0x61, 0x6e, 0x73, 0x76, 0x79, 0x7a, 0x7c, 0x7f,
        };
        static const char sbestr[] = "corrected single";
        static const char dbestr[] = "uncorrectable double";
        static const char mbestr[] = "uncorrectable multiple";

        if (!(address & 0x4))
            syn = chksyn;           /* Low bank. */
        else
            syn = chksyn >> 16;     /* High bank. */

        if (!(syn & KN0X_ESR_VLDLO)) {
            /* Ack now, no rewrite will happen. */
            dec_ecc_be_ack();

            fmt = KERN_ALERT "%s" "invalid\n";
        } else {
            sngl = syn & KN0X_ESR_SNGLO;
            syn &= KN0X_ESR_SYNLO;

            /*
             * Multibit errors may be tagged incorrectly;
             * check the syndrome explicitly.
             */
            for (i = 0; i < 25; i++)
                if (syn == data_mbit[i])
                    break;

            if (i < 25) {
                status = mbestr;
            } else if (!sngl) {
                status = dbestr;
            } else {
                volatile u32 *ptr =
                    (void *)CKSEG1ADDR(address);

                *ptr = *ptr;        /* Rewrite. */
                iob();

                status = sbestr;
                action = MIPS_BE_DISCARD;
            }

            /* Ack now, now we've rewritten (or not). */
            dec_ecc_be_ack();

            if (syn && syn == (syn & -syn)) {
                if (syn == 0x01) {
                    fmt = KERN_ALERT "%s"
                          "%#04x -- %s bit error "
                          "at check bit C%s\n";
                    xbit = "X";
                } else {
                    fmt = KERN_ALERT "%s"
                          "%#04x -- %s bit error "
                          "at check bit C%s%u\n";
                }
                i = syn >> 2;
            } else {
                for (i = 0; i < 32; i++)
                    if (syn == data_sbit[i])
                        break;
                if (i < 32)
                    fmt = KERN_ALERT "%s"
                          "%#04x -- %s bit error "
                          "at data bit D%s%u\n";
                else
                    fmt = KERN_ALERT "%s"
                          "%#04x -- %s bit error\n";
            }
        }
    }

    if (action != MIPS_BE_FIXUP)
        printk(KERN_ALERT "Bus error %s: %s %s %s at %#010lx\n",
            kind, agent, cycle, event, address);

    if (action != MIPS_BE_FIXUP && erraddr & KN0X_EAR_ECCERR)
        printk(fmt, "  ECC syndrome ", syn, status, xbit, i);

    return action;
}

int dec_ecc_be_handler(struct pt_regs *regs, int is_fixup)
{
    return dec_ecc_be_backend(regs, is_fixup, 0);
}

irqreturn_t dec_ecc_be_interrupt(int irq, void *dev_id)
{
    struct pt_regs *regs = get_irq_regs();

    int action = dec_ecc_be_backend(regs, 0, 1);

    if (action == MIPS_BE_DISCARD)
        return IRQ_HANDLED;

    /*
     * FIXME: Find the affected processes and kill them, otherwise
     * we must die.
     *
     * The interrupt is asynchronously delivered thus EPC and RA
     * may be irrelevant, but are printed for a reference.
     */
    printk(KERN_ALERT "Fatal bus interrupt, epc == %08lx, ra == %08lx\n",
           regs->cp0_epc, regs->regs[31]);
    die("Unrecoverable bus error", regs);
}


/*
 * Initialization differs a bit between KN02 and KN03/KN05, so we
 * need two variants.  Once set up, all systems can be handled the
 * same way.
 */
static inline void dec_kn02_be_init(void)
{
    volatile u32 *csr = (void *)CKSEG1ADDR(KN02_SLOT_BASE + KN02_CSR);

    kn0x_erraddr = (void *)CKSEG1ADDR(KN02_SLOT_BASE + KN02_ERRADDR);
    kn0x_chksyn = (void *)CKSEG1ADDR(KN02_SLOT_BASE + KN02_CHKSYN);

    /* Preset write-only bits of the Control Register cache. */
    cached_kn02_csr = *csr | KN02_CSR_LEDS;

    /* Set normal ECC detection and generation. */
    cached_kn02_csr &= ~(KN02_CSR_DIAGCHK | KN02_CSR_DIAGGEN);
    /* Enable ECC correction. */
    cached_kn02_csr |= KN02_CSR_CORRECT;
    *csr = cached_kn02_csr;
    iob();
}

static inline void dec_kn03_be_init(void)
{
    volatile u32 *mcr = (void *)CKSEG1ADDR(KN03_SLOT_BASE + IOASIC_MCR);
    volatile u32 *mbcs = (void *)CKSEG1ADDR(KN4K_SLOT_BASE + KN4K_MB_CSR);

    kn0x_erraddr = (void *)CKSEG1ADDR(KN03_SLOT_BASE + IOASIC_ERRADDR);
    kn0x_chksyn = (void *)CKSEG1ADDR(KN03_SLOT_BASE + IOASIC_CHKSYN);

    /*
     * Set normal ECC detection and generation, enable ECC correction.
     * For KN05 we also need to make sure EE (?) is enabled in the MB.
     * Otherwise DBE/IBE exceptions would be masked but bus error
     * interrupts would still arrive, resulting in an inevitable crash
     * if get_dbe() triggers one.
     */
    *mcr = (*mcr & ~(KN03_MCR_DIAGCHK | KN03_MCR_DIAGGEN)) |
           KN03_MCR_CORRECT;
    if (current_cpu_type() == CPU_R4400SC)
        *mbcs |= KN4K_MB_CSR_EE;
    fast_iob();
}

void __init dec_ecc_be_init(void)
{
    if (mips_machtype == MACH_DS5000_200)
        dec_kn02_be_init();
    else
        dec_kn03_be_init();

    /* Clear any leftover errors from the firmware. */
    dec_ecc_be_ack();
}