From: Zhou Yanjie <zhouyan...@zoho.com>
[ Upstream commit 053951dda71ecb4b554a2cdbe26f5f6f9bee9dd2 ]
In order to further reduce power consumption, the XBurst core
by default attempts to avoid branch target buffer lookups by
detecting & special casing loops. This feature will cause
BogoMIPS and lpj calculate in error. Set cp0 config7 bit 4 to
disable this feature.
Signed-off-by: Zhou Yanjie <zhouyan...@zoho.com>
Signed-off-by: Paul Burton <paul.bur...@mips.com>
Cc: linux-m...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: r...@linux-mips.org
Cc: p...@crapouillou.net
Cc: jho...@kernel.org
Cc: ma...@debian.org
Cc: gre...@linuxfoundation.org
Cc: t...@linutronix.de
Cc: alli...@lohutok.net
Cc: s...@debian.org
Cc: che...@lemote.com
Cc: jiaxun.y...@flygoat.com
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
arch/mips/include/asm/mipsregs.h | 4 ++++
arch/mips/kernel/cpu-probe.c | 7 +++++++
2 files changed, 11 insertions(+)
diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 1e6966e8527e9..bdbdc19a2b8f8 100644
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -689,6 +689,9 @@
#define MIPS_CONF7_IAR (_ULCAST_(1) << 10)
#define MIPS_CONF7_AR (_ULCAST_(1) << 16)
+/* Ingenic Config7 bits */
+#define MIPS_CONF7_BTB_LOOP_EN (_ULCAST_(1) << 4)
+
/* Config7 Bits specific to MIPS Technologies. */
/* Performance counters implemented Per TC */
@@ -2813,6 +2816,7 @@ __BUILD_SET_C0(status)
__BUILD_SET_C0(cause)
__BUILD_SET_C0(config)
__BUILD_SET_C0(config5)
+__BUILD_SET_C0(config7)
__BUILD_SET_C0(intcontrol)
__BUILD_SET_C0(intctl)
__BUILD_SET_C0(srsmap)
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 9635c1db3ae6a..e654ffc1c8a0d 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -1964,6 +1964,13 @@ static inline void cpu_probe_ingenic(struct cpuinfo_mips
*c, unsigned int cpu)
c->cputype = CPU_JZRISC;
c->writecombine = _CACHE_UNCACHED_ACCELERATED;
__cpu_name[cpu] = "Ingenic JZRISC";
+ /*
+ * The XBurst core by default attempts to avoid branch target
+ * buffer lookups by detecting & special casing loops. This
+ * feature will cause BogoMIPS and lpj calculate in error.
+ * Set cp0 config7 bit 4 to disable this feature.
+ */
+ set_c0_config7(MIPS_CONF7_BTB_LOOP_EN);
break;
default:
panic("Unknown Ingenic Processor ID!");
--
2.20.1
