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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>
This commit is contained in:
Markos Chandras 2014-11-10 12:25:34 +00:00 committed by Ralf Baechle
parent 4ec8f9e9b0
commit cf0a8aa022
2 changed files with 34 additions and 1 deletions
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2
arch/mips/include/asm/mipsregs.h
View File

@ -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)

33
arch/mips/kernel/cpu-probe.c
View File

@ -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);