From: Zhou Yanjie zhouyanjie@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 zhouyanjie@zoho.com Signed-off-by: Paul Burton paul.burton@mips.com Cc: linux-mips@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: ralf@linux-mips.org Cc: paul@crapouillou.net Cc: jhogan@kernel.org Cc: malat@debian.org Cc: gregkh@linuxfoundation.org Cc: tglx@linutronix.de Cc: allison@lohutok.net Cc: syq@debian.org Cc: chenhc@lemote.com Cc: jiaxun.yang@flygoat.com Signed-off-by: Sasha Levin sashal@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 01df9ad62fb83..1bb9448777c5c 100644 --- a/arch/mips/include/asm/mipsregs.h +++ b/arch/mips/include/asm/mipsregs.h @@ -688,6 +688,9 @@ #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 */ @@ -2774,6 +2777,7 @@ __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 d535fc706a8b3..25cd8737e7fe0 100644 --- a/arch/mips/kernel/cpu-probe.c +++ b/arch/mips/kernel/cpu-probe.c @@ -1879,6 +1879,13 @@ 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!");