Some machines want to implement their own __delay() routine based on fixed rate timers. Expose functionality to set the __delay() routine at runtime. This should allow two machines with different __delay() routines to happily co-exist within the same kernel with minimal overhead. Russell expressed concern that using a timer based __delay() would cause problems when an iomapped device isn't mapped in prior to a delay call being made (see http://article.gmane.org/gmane.linux.ports.arm.kernel/78543 for more info). We can sidestep that issue with this approach since the __delay() routine _should_ only be pointed to a timer based delay once the timer has been properly mapped. Up until that point __delay() and udelay() will use delay_loop() which is always safe to call. This patch is inspired by x86's delay.c Reviewed-by: Saravana Kannan <skannan@xxxxxxxxxxxxxx> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx> --- Changed to inline set_delay_fn() arch/arm/include/asm/delay.h | 7 +++++++ arch/arm/lib/delay.c | 14 +++++++++++--- 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index ccc5ed5..82ef82a 100644 --- a/arch/arm/include/asm/delay.h +++ b/arch/arm/include/asm/delay.h @@ -40,5 +40,12 @@ extern void __const_udelay(unsigned long); __const_udelay((n) * ((2199023U*HZ)>>11))) : \ __udelay(n)) +extern void (*delay_fn)(unsigned long); + +static inline void set_delay_fn(void (*fn)(unsigned long)) +{ + delay_fn = fn; +} + #endif /* defined(_ARM_DELAY_H) */ diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c index f92aca0..7468bc6 100644 --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -11,11 +11,9 @@ #include <linux/delay.h> /* - * loops = usecs * HZ * loops_per_jiffy / 1000000 - * * Oh, if only we had a cycle counter... */ -void __delay(unsigned long loops) +static void delay_loop(unsigned long loops) { asm volatile( "1: subs %0, %0, #1 \n" @@ -24,6 +22,16 @@ void __delay(unsigned long loops) : "r" (loops) ); } + +void (*delay_fn)(unsigned long) = delay_loop; + +/* + * loops = usecs * HZ * loops_per_jiffy / 1000000 + */ +void __delay(unsigned long loops) +{ + delay_fn(loops); +} EXPORT_SYMBOL(__delay); /* -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
