From 625c0a21700bdb90844d926a1508a17a77e369c9 Mon Sep 17 00:00:00 2001 From: "Steven J. Hill" Date: Tue, 28 Aug 2012 23:20:08 -0500 Subject: MIPS: Avoid pipeline stalls on some MIPS32R2 cores. The architecture specification says that an EHB instruction is needed to avoid a hazard when writing TLB entries. However, some cores do not have this hazard, and thus the EHB instruction causes a costly pipeline stall. Detect these cores and do not use the EHB instruction. Signed-off-by: Steven J. Hill --- arch/mips/mm/tlbex.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'arch/mips/mm') diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c index 03eb0ef9158..22ba108d708 100644 --- a/arch/mips/mm/tlbex.c +++ b/arch/mips/mm/tlbex.c @@ -449,8 +449,20 @@ static void __cpuinit build_tlb_write_entry(u32 **p, struct uasm_label **l, } if (cpu_has_mips_r2) { - if (cpu_has_mips_r2_exec_hazard) + /* + * The architecture spec says an ehb is required here, + * but a number of cores do not have the hazard and + * using an ehb causes an expensive pipeline stall. + */ + switch (current_cpu_type()) { + case CPU_M14KC: + case CPU_74K: + break; + + default: uasm_i_ehb(p); + break; + } tlbw(p); return; } -- cgit v1.2.3-70-g09d2