3.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Markos Chandras <markos.chandras@xxxxxxxxxx> commit cf0a8aa0226da5de88011e7f30eff22a894b2f49 upstream. 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 <markos.chandras@xxxxxxxxxx> Reviewed-by: James Hogan <james.hogan@xxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxx Patchwork: https://patchwork.linux-mips.org/patch/8368/ Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/mips/include/asm/mipsregs.h | 2 ++ arch/mips/kernel/cpu-probe.c | 33 ++++++++++++++++++++++++++++++++- 2 files changed, 34 insertions(+), 1 deletion(-) --- 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) --- a/arch/mips/kernel/cpu-probe.c +++ b/arch/mips/kernel/cpu-probe.c @@ -192,6 +192,32 @@ static void set_isa(struct cpuinfo_mips 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; @@ -202,9 +228,14 @@ static void set_ftlb_enable(struct cpuin 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);
