This is a note to let you know that I have just added a patch titled
MIPS: cpu-probe: Set the FTLB probability bit on supported cores
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt3.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From a5ebd9ddc81f751cf39f712abe24443223f7ccc0 Mon Sep 17 00:00:00 2001
From: Markos Chandras <markos.chandras@xxxxxxxxxx>
Date: Mon, 10 Nov 2014 12:25:34 +0000
Subject: MIPS: cpu-probe: Set the FTLB probability bit on supported cores
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: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
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 98e9754a4b6b..6ad0208b50fb 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -660,6 +660,8 @@
#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 d74f957c561e..d5006d23ca7b 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -179,6 +179,32 @@ 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;
@@ -189,9 +215,14 @@ 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);
