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[MIPS] Workaround for 4Kc machine check exception

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Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Maciej W. Rozycki 2006-08-23 14:26:50 +01:00 committed by Ralf Baechle
parent 48d480b0bd
commit 8df5beac2a
1 changed files with 25 additions and 1 deletions
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26
arch/mips/mm/tlbex.c
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@ -57,6 +57,21 @@ static __init int __maybe_unused r10000_llsc_war(void)
return R10000_LLSC_WAR;
}
/*
* Found by experiment: At least some revisions of the 4kc throw under
* some circumstances a machine check exception, triggered by invalid
* values in the index register. Delaying the tlbp instruction until
* after the next branch, plus adding an additional nop in front of
* tlbwi/tlbwr avoids the invalid index register values. Nobody knows
* why; it's not an issue caused by the core RTL.
*
*/
static __init int __attribute__((unused)) m4kc_tlbp_war(void)
{
return (current_cpu_data.processor_id & 0xffff00) ==
(PRID_COMP_MIPS | PRID_IMP_4KC);
}
/*
* A little micro-assembler, intended for TLB refill handler
* synthesizing. It is intentionally kept simple, does only support
@ -894,6 +909,8 @@ static __init void build_tlb_write_entry(u32 **p, struct label **l,
case CPU_20KC:
case CPU_25KF:
case CPU_LOONGSON2:
if (m4kc_tlbp_war())
i_nop(p);
tlbw(p);
break;
@ -1705,7 +1722,8 @@ build_r4000_tlbchange_handler_head(u32 **p, struct label **l,
l_smp_pgtable_change(l, *p);
# endif
iPTE_LW(p, l, pte, ptr); /* get even pte */
build_tlb_probe_entry(p);
if (!m4kc_tlbp_war())
build_tlb_probe_entry(p);
}
static void __init
@ -1747,6 +1765,8 @@ static void __init build_r4000_tlb_load_handler(void)
build_r4000_tlbchange_handler_head(&p, &l, &r, K0, K1);
build_pte_present(&p, &l, &r, K0, K1, label_nopage_tlbl);
if (m4kc_tlbp_war())
build_tlb_probe_entry(&p);
build_make_valid(&p, &r, K0, K1);
build_r4000_tlbchange_handler_tail(&p, &l, &r, K0, K1);
@ -1781,6 +1801,8 @@ static void __init build_r4000_tlb_store_handler(void)
build_r4000_tlbchange_handler_head(&p, &l, &r, K0, K1);
build_pte_writable(&p, &l, &r, K0, K1, label_nopage_tlbs);
if (m4kc_tlbp_war())
build_tlb_probe_entry(&p);
build_make_write(&p, &r, K0, K1);
build_r4000_tlbchange_handler_tail(&p, &l, &r, K0, K1);
@ -1815,6 +1837,8 @@ static void __init build_r4000_tlb_modify_handler(void)
build_r4000_tlbchange_handler_head(&p, &l, &r, K0, K1);
build_pte_modifiable(&p, &l, &r, K0, K1, label_nopage_tlbm);
if (m4kc_tlbp_war())
build_tlb_probe_entry(&p);
/* Present and writable bits set, set accessed and dirty bits. */
build_make_write(&p, &r, K0, K1);
build_r4000_tlbchange_handler_tail(&p, &l, &r, K0, K1);