The FTLBP field in Config7 for the I6400 is intended as chicken bits for
debugging rather than as a field that software actually makes use of.
For best performance, FTLBP should be left at its default value of 0
with all TLB writes hitting the FTLB by default.
Additionally, since set_ftlb_enable is called from decode_configs before
decode_config4 which determines the size of the TLBs, this was
previously always setting FTLBP=3 for a 3:1 FTLB:VTLB write ratio which
makes abysmal use of the available FTLB resources.
This effectively reverts b0c4e1b79d8a ("MIPS: Set up FTLB probability
for I6400").
Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
Cc: Markos Chandras <markos.chandras@xxxxxxxxxx>
Fixes: b0c4e1b79d8a ("MIPS: Set up FTLB probability for I6400")
---
arch/mips/include/asm/mipsregs.h | 2 --
arch/mips/kernel/cpu-probe.c | 9 ++-------
2 files changed, 2 insertions(+), 9 deletions(-)
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index e1ca65c..f78f0b3 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -659,8 +659,6 @@
#define MIPS_CONF7_IAR (_ULCAST_(1) << 10)
#define MIPS_CONF7_AR (_ULCAST_(1) << 16)
-/* FTLB probability bits for R6 */
-#define MIPS_CONF7_FTLBP_SHIFT (18)
/* WatchLo* register definitions */
#define MIPS_WATCHLO_IRW (_ULCAST_(0x7) << 0)
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index a88d442..ae29050 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -555,13 +555,8 @@ static int set_ftlb_enable(struct cpuinfo_mips *c, int enable)
write_c0_config6(config & ~MIPS_CONF6_FTLBEN);
break;
case CPU_I6400:
- /* I6400 & related cores use Config7 to configure FTLB */
- config = read_c0_config7();
- /* Clear the old probability value */
- config &= ~(3 << MIPS_CONF7_FTLBP_SHIFT);
- write_c0_config7(config | (calculate_ftlb_probability(c)
- << MIPS_CONF7_FTLBP_SHIFT));
- break;
+ /* There's no way to disable the FTLB */
+ return !enable;
case CPU_LOONGSON3:
/* Flush ITLB, DTLB, VTLB and FTLB */
write_c0_diag(LOONGSON_DIAG_ITLB | LOONGSON_DIAG_DTLB |
--
2.9.3
