From mboxrd@z Thu Jan 1 00:00:00 1970 From: ccross@android.com (Colin Cross) Date: Thu, 29 Apr 2010 02:08:24 -0700 Subject: [PATCH] [ARM] Add ARCH_PROVIDES_UDELAY config option In-Reply-To: <> References: <> Message-ID: <1272532104-20074-1-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, leading to udelays that are too long if the CPU frequency is scaled down from the frequency at loops_per_jiffy calibration, 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