From mboxrd@z Thu Jan 1 00:00:00 1970 From: ccross@android.com (Colin Cross) Date: Fri, 30 Apr 2010 12:12:16 -0700 Subject: [PATCH V2] [ARM] Add ARCH_PROVIDES_UDELAY config option In-Reply-To: <> References: <> Message-ID: <1272654736-28837-1-git-send-email-ccross@android.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On SMP kernels, the loops_per_jiffy value is not scaled due to the possibility of one CPU affecting the speed of another CPU while the second CPU is in a udelay loop. Since loops_per_jiffy is calculated once on boot for SMP kernels, udelays are too long if the CPU frequency is scaled down from the boot frequency, or too short if the frequency is scaled up. Some SOCs have a timer with a constant tick rate that can be used to time udelays, similar to the TSC on x86. Provide a config flag to allow these SOCs to override the default ARM udelay implementation. Signed-off-by: Colin Cross --- arch/arm/Kconfig | 3 +++ arch/arm/include/asm/delay.h | 4 ++++ arch/arm/lib/Makefile | 6 +++++- 3 files changed, 12 insertions(+), 1 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 33d2825..d9923b0 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -175,6 +175,9 @@ config ARM_L1_CACHE_SHIFT_6 help Setting ARM L1 cache line size to 64 Bytes. +config ARCH_PROVIDES_UDELAY + bool + if OPROFILE config OPROFILE_ARMV6 diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index b2deda1..57f1fa0 100644 --- a/arch/arm/include/asm/delay.h +++ b/arch/arm/include/asm/delay.h @@ -8,6 +8,9 @@ #include /* HZ */ +#ifdef CONFIG_ARCH_PROVIDES_UDELAY +#include +#else extern void __delay(int loops); /* @@ -40,5 +43,6 @@ extern void __const_udelay(unsigned long); __const_udelay((n) * ((2199023U*HZ)>>11))) : \ __udelay(n)) +#endif /* defined(ARCH_PROVIDES_UDELAY) */ #endif /* defined(_ARM_DELAY_H) */ diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile index 030ba72..aa449e3 100644 --- a/arch/arm/lib/Makefile +++ b/arch/arm/lib/Makefile @@ -6,7 +6,7 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \ csumpartialcopy.o csumpartialcopyuser.o clearbit.o \ - delay.o findbit.o memchr.o memcpy.o \ + findbit.o memchr.o memcpy.o \ memmove.o memset.o memzero.o setbit.o \ strncpy_from_user.o strnlen_user.o \ strchr.o strrchr.o \ @@ -17,6 +17,10 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \ mmu-y := clear_user.o copy_page.o getuser.o putuser.o +ifneq ($(CONFIG_ARCH_PROVIDES_UDELAY),y) + lib-y += delay.o +endif + # the code in uaccess.S is not preemption safe and # probably faster on ARMv3 only ifeq ($(CONFIG_PREEMPT),y) -- 1.5.4.3