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path: root/drivers/gpio/gpio-ts4900.c
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Diffstat (limited to 'drivers/gpio/gpio-ts4900.c')
-rw-r--r--drivers/gpio/gpio-ts4900.c24
1 files changed, 19 insertions, 5 deletions
diff --git a/drivers/gpio/gpio-ts4900.c b/drivers/gpio/gpio-ts4900.c
index 1da8d0586329..410452306bf7 100644
--- a/drivers/gpio/gpio-ts4900.c
+++ b/drivers/gpio/gpio-ts4900.c
@@ -1,7 +1,7 @@
/*
* 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
@@ -52,19 +52,33 @@ 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 potential issue
+ * with OE and data 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
+ * proper data bit to what is requested and then set OE bit. This
+ * prevents a glitch that can occur on the IO line
+ */
+ regmap_read(priv->regmap, offset, &reg);
+ 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);