MIPS: Stop setting I6400 FTLBP
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@imgtec.com>
Fixes: b0c4e1b79d8a ("MIPS: Set up FTLB probability for I6400")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14021/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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 @@
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 |