arch/mips/dec/kn01-berr.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      Bus error event handling code for DECstation/DECsystem 3100
   4  *      and 2100 (KN01) systems equipped with parity error detection
   5  *      logic.
   6  *
   7  *      Copyright (c) 2005  Maciej W. Rozycki
   8  */
   9
  10 #include <linux/init.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/kernel.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/types.h>
  15
  16 #include <asm/inst.h>
  17 #include <asm/irq_regs.h>
  18 #include <asm/mipsregs.h>
  19 #include <asm/page.h>
  20 #include <asm/ptrace.h>
  21 #include <asm/traps.h>
  22 #include <linux/uaccess.h>
  23
  24 #include <asm/dec/kn01.h>
  25
  26
  27 /* CP0 hazard avoidance. */
  28 #define BARRIER                         \
  29         __asm__ __volatile__(           \
  30                 ".set   push\n\t"       \
  31                 ".set   noreorder\n\t"  \
  32                 "nop\n\t"               \
  33                 ".set   pop\n\t")
  34
  35 /*
  36  * Bits 7:0 of the Control Register are write-only -- the
  37  * corresponding bits of the Status Register have a different
  38  * meaning.  Hence we use a cache.  It speeds up things a bit
  39  * as well.
  40  *
  41  * There is no default value -- it has to be initialized.
  42  */
  43 u16 cached_kn01_csr;
  44 static DEFINE_RAW_SPINLOCK(kn01_lock);
  45
  46
  47 static inline void dec_kn01_be_ack(void)
  48 {
  49         volatile u16 *csr = (void *)CKSEG1ADDR(KN01_SLOT_BASE + KN01_CSR);
  50         unsigned long flags;
  51
  52         raw_spin_lock_irqsave(&kn01_lock, flags);
  53
  54         *csr = cached_kn01_csr | KN01_CSR_MEMERR;       /* Clear bus IRQ. */
  55         iob();
  56
  57         raw_spin_unlock_irqrestore(&kn01_lock, flags);
  58 }
  59
  60 static int dec_kn01_be_backend(struct pt_regs *regs, int is_fixup, int invoker)
  61 {
  62         volatile u32 *kn01_erraddr = (void *)CKSEG1ADDR(KN01_SLOT_BASE +
  63                                                         KN01_ERRADDR);
  64
  65         static const char excstr[] = "exception";
  66         static const char intstr[] = "interrupt";
  67         static const char cpustr[] = "CPU";
  68         static const char mreadstr[] = "memory read";
  69         static const char readstr[] = "read";
  70         static const char writestr[] = "write";
  71         static const char timestr[] = "timeout";
  72         static const char paritystr[] = "parity error";
  73
  74         int data = regs->cp0_cause & 4;
  75         unsigned int __user *pc = (unsigned int __user *)regs->cp0_epc +
  76                                   ((regs->cp0_cause & CAUSEF_BD) != 0);
  77         union mips_instruction insn;
  78         unsigned long entrylo, offset;
  79         long asid, entryhi, vaddr;
  80
  81         const char *kind, *agent, *cycle, *event;
  82         unsigned long address;
  83
  84         u32 erraddr = *kn01_erraddr;
  85         int action = MIPS_BE_FATAL;
  86
  87         /* Ack ASAP, so that any subsequent errors get caught. */
  88         dec_kn01_be_ack();
  89
  90         kind = invoker ? intstr : excstr;
  91
  92         agent = cpustr;
  93
  94         if (invoker)
  95                 address = erraddr;
  96         else {
  97                 /* Bloody hardware doesn't record the address for reads... */
  98                 if (data) {
  99                         /* This never faults. */
 100                         __get_user(insn.word, pc);
 101                         vaddr = regs->regs[insn.i_format.rs] +
 102                                 insn.i_format.simmediate;
 103                 } else
 104                         vaddr = (long)pc;
 105                 if (KSEGX(vaddr) == CKSEG0 || KSEGX(vaddr) == CKSEG1)
 106                         address = CPHYSADDR(vaddr);
 107                 else {
 108                         /* Peek at what physical address the CPU used. */
 109                         asid = read_c0_entryhi();
 110                         entryhi = asid & (PAGE_SIZE - 1);
 111                         entryhi |= vaddr & ~(PAGE_SIZE - 1);
 112                         write_c0_entryhi(entryhi);
 113                         BARRIER;
 114                         tlb_probe();
 115                         /* No need to check for presence. */
 116                         tlb_read();
 117                         entrylo = read_c0_entrylo0();
 118                         write_c0_entryhi(asid);
 119                         offset = vaddr & (PAGE_SIZE - 1);
 120                         address = (entrylo & ~(PAGE_SIZE - 1)) | offset;
 121                 }
 122         }
 123
 124         /* Treat low 256MB as memory, high -- as I/O. */
 125         if (address < 0x10000000) {
 126                 cycle = mreadstr;
 127                 event = paritystr;
 128         } else {
 129                 cycle = invoker ? writestr : readstr;
 130                 event = timestr;
 131         }
 132
 133         if (is_fixup)
 134                 action = MIPS_BE_FIXUP;
 135
 136         if (action != MIPS_BE_FIXUP)
 137                 printk(KERN_ALERT "Bus error %s: %s %s %s at %#010lx\n",
 138                         kind, agent, cycle, event, address);
 139
 140         return action;
 141 }
 142
 143 int dec_kn01_be_handler(struct pt_regs *regs, int is_fixup)
 144 {
 145         return dec_kn01_be_backend(regs, is_fixup, 0);
 146 }
 147
 148 irqreturn_t dec_kn01_be_interrupt(int irq, void *dev_id)
 149 {
 150         volatile u16 *csr = (void *)CKSEG1ADDR(KN01_SLOT_BASE + KN01_CSR);
 151         struct pt_regs *regs = get_irq_regs();
 152         int action;
 153
 154         if (!(*csr & KN01_CSR_MEMERR))
 155                 return IRQ_NONE;                /* Must have been video. */
 156
 157         action = dec_kn01_be_backend(regs, 0, 1);
 158
 159         if (action == MIPS_BE_DISCARD)
 160                 return IRQ_HANDLED;
 161
 162         /*
 163          * FIXME: Find the affected processes and kill them, otherwise
 164          * we must die.
 165          *
 166          * The interrupt is asynchronously delivered thus EPC and RA
 167          * may be irrelevant, but are printed for a reference.
 168          */
 169         printk(KERN_ALERT "Fatal bus interrupt, epc == %08lx, ra == %08lx\n",
 170                regs->cp0_epc, regs->regs[31]);
 171         die("Unrecoverable bus error", regs);
 172 }
 173
 174
 175 void __init dec_kn01_be_init(void)
 176 {
 177         volatile u16 *csr = (void *)CKSEG1ADDR(KN01_SLOT_BASE + KN01_CSR);
 178         unsigned long flags;
 179
 180         raw_spin_lock_irqsave(&kn01_lock, flags);
 181
 182         /* Preset write-only bits of the Control Register cache. */
 183         cached_kn01_csr = *csr;
 184         cached_kn01_csr &= KN01_CSR_STATUS | KN01_CSR_PARDIS | KN01_CSR_TXDIS;
 185         cached_kn01_csr |= KN01_CSR_LEDS;
 186
 187         /* Enable parity error detection. */
 188         cached_kn01_csr &= ~KN01_CSR_PARDIS;
 189         *csr = cached_kn01_csr;
 190         iob();
 191
 192         raw_spin_unlock_irqrestore(&kn01_lock, flags);
 193
 194         /* Clear any leftover errors from the firmware. */
 195         dec_kn01_be_ack();
 196 }