diff options
Diffstat (limited to 'drivers/gpio/gpio-ts4900.c')
| -rw-r--r-- | drivers/gpio/gpio-ts4900.c | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/drivers/gpio/gpio-ts4900.c b/drivers/gpio/gpio-ts4900.c index d885032cf814..416725c26e94 100644 --- a/drivers/gpio/gpio-ts4900.c +++ b/drivers/gpio/gpio-ts4900.c @@ -1,17 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0 /* * Digital I/O driver for Technologic Systems I2C FPGA Core * - * Copyright (C) 2015 Technologic Systems + * Copyright (C) 2015, 2018 Technologic Systems * Copyright (C) 2016 Savoir-Faire Linux - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * - * This program is distributed "as is" WITHOUT ANY WARRANTY of any - * kind, whether expressed or implied; without even the implied warranty - * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License version 2 for more details. */ #include <linux/gpio/driver.h> @@ -56,18 +48,34 @@ static int ts4900_gpio_direction_input(struct gpio_chip *chip, struct ts4900_gpio_priv *priv = gpiochip_get_data(chip); /* - * This will clear the output enable bit, the other bits are - * dontcare when this is cleared + * Only clear the OE bit here, requires a RMW. Prevents a potential issue + * with OE and DAT getting to the physical pin at different times. */ - return regmap_write(priv->regmap, offset, 0); + return regmap_update_bits(priv->regmap, offset, TS4900_GPIO_OE, 0); } static int ts4900_gpio_direction_output(struct gpio_chip *chip, unsigned int offset, int value) { struct ts4900_gpio_priv *priv = gpiochip_get_data(chip); + unsigned int reg; int ret; + /* + * If changing from an input to an output, we need to first set the + * GPIO's DAT bit to what is requested and then set the OE bit. This + * prevents a glitch that can occur on the IO line. + */ + regmap_read(priv->regmap, offset, ®); + if (!(reg & TS4900_GPIO_OE)) { + if (value) + reg = TS4900_GPIO_OUT; + else + reg &= ~TS4900_GPIO_OUT; + + regmap_write(priv->regmap, offset, reg); + } + if (value) ret = regmap_write(priv->regmap, offset, TS4900_GPIO_OE | TS4900_GPIO_OUT); |