diff options
| author | Markos Chandras <markos.chandras@imgtec.com> | 2014-11-10 12:25:34 +0000 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2014-11-24 07:44:05 +0100 |
| commit | cf0a8aa0226da5de88011e7f30eff22a894b2f49 (patch) | |
| tree | b508470022cd20f8cf0fcb8be10ee7f2904e07bc /arch/mips/kernel/cpu-probe.c | |
| parent | 4ec8f9e9b08451303253249e4e302f10ee23d565 (diff) | |
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 <markos.chandras@imgtec.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: <stable@vger.kernel.org> # v3.15+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8368/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/kernel/cpu-probe.c')
| -rw-r--r-- | arch/mips/kernel/cpu-probe.c | 33 |
1 files changed, 32 insertions, 1 deletions
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); |