From cf0a8aa0226da5de88011e7f30eff22a894b2f49 Mon Sep 17 00:00:00 2001 From: Markos Chandras Date: Mon, 10 Nov 2014 12:25:34 +0000 Subject: [PATCH] MIPS: cpu-probe: Set the FTLB probability bit on supported cores Make use of the Config6/FLTBP bit to set the probability of a TLBWR instruction to hit the FTLB or the VTLB. A value of 0 (which may be the default value on certain cores, such as proAptiv or P5600) means that a TLBWR instruction will never hit the VTLB which leads to performance limitations since it effectively decreases the number of available TLB slots. Signed-off-by: Markos Chandras Reviewed-by: James Hogan Cc: # v3.15+ Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/8368/ Signed-off-by: Ralf Baechle --- arch/mips/include/asm/mipsregs.h | 2 ++ arch/mips/kernel/cpu-probe.c | 33 +++++++++++++++++++++++++++++++- 2 files changed, 34 insertions(+), 1 deletion(-) diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h index b46cd220a018..22a135ac91de 100644 --- a/arch/mips/include/asm/mipsregs.h +++ b/arch/mips/include/asm/mipsregs.h @@ -661,6 +661,8 @@ #define MIPS_CONF6_SYND (_ULCAST_(1) << 13) /* proAptiv FTLB on/off bit */ #define MIPS_CONF6_FTLBEN (_ULCAST_(1) << 15) +/* FTLB probability bits */ +#define MIPS_CONF6_FTLBP_SHIFT (16) #define MIPS_CONF7_WII (_ULCAST_(1) << 31) diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c index d5a4f380b019..dc49cf30c2db 100644 --- a/arch/mips/kernel/cpu-probe.c +++ b/arch/mips/kernel/cpu-probe.c @@ -193,6 +193,32 @@ static void set_isa(struct cpuinfo_mips *c, unsigned int isa) static char unknown_isa[] = KERN_ERR \ "Unsupported ISA type, c0.config0: %d."; +static unsigned int calculate_ftlb_probability(struct cpuinfo_mips *c) +{ + + unsigned int probability = c->tlbsize / c->tlbsizevtlb; + + /* + * 0 = All TLBWR instructions go to FTLB + * 1 = 15:1: For every 16 TBLWR instructions, 15 go to the + * FTLB and 1 goes to the VTLB. + * 2 = 7:1: As above with 7:1 ratio. + * 3 = 3:1: As above with 3:1 ratio. + * + * Use the linear midpoint as the probability threshold. + */ + if (probability >= 12) + return 1; + else if (probability >= 6) + return 2; + else + /* + * So FTLB is less than 4 times bigger than VTLB. + * A 3:1 ratio can still be useful though. + */ + return 3; +} + static void set_ftlb_enable(struct cpuinfo_mips *c, int enable) { unsigned int config6; @@ -203,9 +229,14 @@ static void set_ftlb_enable(struct cpuinfo_mips *c, int enable) case CPU_P5600: /* proAptiv & related cores use Config6 to enable the FTLB */ config6 = read_c0_config6(); + /* Clear the old probability value */ + config6 &= ~(3 << MIPS_CONF6_FTLBP_SHIFT); if (enable) /* Enable FTLB */ - write_c0_config6(config6 | MIPS_CONF6_FTLBEN); + write_c0_config6(config6 | + (calculate_ftlb_probability(c) + << MIPS_CONF6_FTLBP_SHIFT) + | MIPS_CONF6_FTLBEN); else /* Disable FTLB */ write_c0_config6(config6 & ~MIPS_CONF6_FTLBEN);