From 28735a7253a6c24364765e80a5428b4a151fccc2 Mon Sep 17 00:00:00 2001 From: David Brownell Date: Fri, 16 Mar 2007 13:38:14 -0800 Subject: [PATCH] gpio_direction_output() needs an initial value It's been pointed out that output GPIOs should have an initial value, to avoid signal glitching ... among other things, it can be some time before a driver is ready. This patch corrects that oversight, fixing - documentation - platforms supporting the GPIO interface - users of that call (just one for now, others are pending) There's only one user of this call for now since most platforms are still using non-generic GPIO setup code, which in most cases already couples the initial value with its "set output mode" request. Note that most platforms are clear about the hardware letting the output value be set before the pin direction is changed, but the s3c241x docs are vague on that topic ... so those chips might not avoid the glitches. Signed-off-by: David Brownell Acked-by: Andrew Victor Acked-by: Milan Svoboda Acked-by: Haavard Skinnemoen Cc: Russell King Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-arm/arch-at91/gpio.h | 2 +- include/asm-arm/arch-omap/gpio.h | 3 ++- include/asm-arm/arch-pxa/gpio.h | 4 ++-- include/asm-arm/arch-s3c2410/gpio.h | 4 +++- include/asm-arm/arch-sa1100/gpio.h | 2 +- include/asm-avr32/arch-at32ap/gpio.h | 2 +- 6 files changed, 10 insertions(+), 7 deletions(-) (limited to 'include') diff --git a/include/asm-arm/arch-at91/gpio.h b/include/asm-arm/arch-at91/gpio.h index 98ad2114f43..0a241e2fb67 100644 --- a/include/asm-arm/arch-at91/gpio.h +++ b/include/asm-arm/arch-at91/gpio.h @@ -223,7 +223,7 @@ static inline void gpio_free(unsigned gpio) } extern int gpio_direction_input(unsigned gpio); -extern int gpio_direction_output(unsigned gpio); +extern int gpio_direction_output(unsigned gpio, int value); static inline int gpio_get_value(unsigned gpio) { diff --git a/include/asm-arm/arch-omap/gpio.h b/include/asm-arm/arch-omap/gpio.h index 3762a6ae6a7..590917efc94 100644 --- a/include/asm-arm/arch-omap/gpio.h +++ b/include/asm-arm/arch-omap/gpio.h @@ -113,8 +113,9 @@ static inline int gpio_direction_input(unsigned gpio) return __gpio_set_direction(gpio, 1); } -static inline int gpio_direction_output(unsigned gpio) +static inline int gpio_direction_output(unsigned gpio, int value) { + omap_set_gpio_dataout(gpio, value); return __gpio_set_direction(gpio, 0); } diff --git a/include/asm-arm/arch-pxa/gpio.h b/include/asm-arm/arch-pxa/gpio.h index 3d348a35115..aeba24347f8 100644 --- a/include/asm-arm/arch-pxa/gpio.h +++ b/include/asm-arm/arch-pxa/gpio.h @@ -43,9 +43,9 @@ static inline int gpio_direction_input(unsigned gpio) return pxa_gpio_mode(gpio | GPIO_IN); } -static inline int gpio_direction_output(unsigned gpio) +static inline int gpio_direction_output(unsigned gpio, int value) { - return pxa_gpio_mode(gpio | GPIO_OUT); + return pxa_gpio_mode(gpio | GPIO_OUT | (value ? 0 : GPIO_DFLT_LOW)); } static inline int __gpio_get_value(unsigned gpio) diff --git a/include/asm-arm/arch-s3c2410/gpio.h b/include/asm-arm/arch-s3c2410/gpio.h index d47ae453f8c..7583895fd33 100644 --- a/include/asm-arm/arch-s3c2410/gpio.h +++ b/include/asm-arm/arch-s3c2410/gpio.h @@ -44,9 +44,11 @@ static inline int gpio_direction_input(unsigned gpio) return 0; } -static inline int gpio_direction_output(unsigned gpio) +static inline int gpio_direction_output(unsigned gpio, int value) { s3c2410_gpio_cfgpin(gpio, S3C2410_GPIO_OUTPUT); + /* REVISIT can we write the value first, to avoid glitching? */ + s3c2410_gpio_setpin(gpio, value); return 0; } diff --git a/include/asm-arm/arch-sa1100/gpio.h b/include/asm-arm/arch-sa1100/gpio.h index da7575b0e5d..e7a9d26e22a 100644 --- a/include/asm-arm/arch-sa1100/gpio.h +++ b/include/asm-arm/arch-sa1100/gpio.h @@ -38,7 +38,7 @@ static inline void gpio_free(unsigned gpio) } extern int gpio_direction_input(unsigned gpio); -extern int gpio_direction_output(unsigned gpio); +extern int gpio_direction_output(unsigned gpio, int value); static inline int gpio_get_value(unsigned gpio) diff --git a/include/asm-avr32/arch-at32ap/gpio.h b/include/asm-avr32/arch-at32ap/gpio.h index fcb756bdaa8..80a21aa9ae7 100644 --- a/include/asm-avr32/arch-at32ap/gpio.h +++ b/include/asm-avr32/arch-at32ap/gpio.h @@ -10,7 +10,7 @@ int __must_check gpio_request(unsigned int gpio, const char *label); void gpio_free(unsigned int gpio); int gpio_direction_input(unsigned int gpio); -int gpio_direction_output(unsigned int gpio); +int gpio_direction_output(unsigned int gpio, int value); int gpio_get_value(unsigned int gpio); void gpio_set_value(unsigned int gpio, int value); -- cgit v1.2.3