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