28735a7253
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 <dbrownell@users.sourceforge.net> Acked-by: Andrew Victor <andrew@sanpeople.com> Acked-by: Milan Svoboda <msvoboda@ra.rockwell.com> Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
68 lines
1.8 KiB
C
68 lines
1.8 KiB
C
/*
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* linux/include/asm-arm/arch-s3c2410/gpio.h
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*
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* S3C2410 GPIO wrappers for arch-neutral GPIO calls
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*
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* Written by Philipp Zabel <philipp.zabel@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#ifndef __ASM_ARCH_S3C2410_GPIO_H
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#define __ASM_ARCH_S3C2410_GPIO_H
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#include <asm/irq.h>
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#include <asm/hardware.h>
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#include <asm/arch/regs-gpio.h>
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static inline int gpio_request(unsigned gpio, const char *label)
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{
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return 0;
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}
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static inline void gpio_free(unsigned gpio)
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{
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return;
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}
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static inline int gpio_direction_input(unsigned gpio)
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{
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s3c2410_gpio_cfgpin(gpio, S3C2410_GPIO_INPUT);
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return 0;
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}
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static inline int gpio_direction_output(unsigned gpio, int value)
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{
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s3c2410_gpio_cfgpin(gpio, S3C2410_GPIO_OUTPUT);
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/* REVISIT can we write the value first, to avoid glitching? */
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s3c2410_gpio_setpin(gpio, value);
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return 0;
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}
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#define gpio_get_value(gpio) s3c2410_gpio_getpin(gpio)
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#define gpio_set_value(gpio,value) s3c2410_gpio_setpin(gpio, value)
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#include <asm-generic/gpio.h> /* cansleep wrappers */
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#ifdef CONFIG_CPU_S3C2400
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#define gpio_to_irq(gpio) s3c2400_gpio_getirq(gpio)
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#else
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#define gpio_to_irq(gpio) s3c2410_gpio_getirq(gpio)
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#endif
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/* FIXME implement irq_to_gpio() */
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#endif
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