[PATCH 2/7] gpiolib: regmap: add GPIO_REGMAP_QUIRK_SET_AFTER_DIR

[Long Zhao via B4 Relay <devnull+longzhao.ambarella.com@kernel.org>]

From: Long Zhao <longzhao@ambarella.com>

Some controllers ignore output writes while a line is still an input.
Add a behaviour flag so the output value is written after the direction
change. This is a legacy quirk. New hardware must not use it.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Long Zhao <longzhao@ambarella.com>
---
 drivers/gpio/gpio-regmap.c  | 15 +++++++++++++--
 include/linux/gpio/regmap.h | 14 ++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index 51b4d69b8740..0a44deae3d01 100644
--- a/drivers/gpio/gpio-regmap.c
+++ b/drivers/gpio/gpio-regmap.c
@@ -33,6 +33,7 @@ struct gpio_regmap {
 	unsigned int reg_dir_out_base;
 	unsigned long *fixed_direction_mask;
 	unsigned long *fixed_direction_output;
+	unsigned long quirks;
 
 #ifdef CONFIG_REGMAP_IRQ
 	int regmap_irq_line;
@@ -271,9 +272,17 @@ static int gpio_regmap_direction_output(struct gpio_chip *chip,
 			return ret;
 	}
 
-	gpio_regmap_set(chip, offset, value);
+	if (!(gpio->quirks & GPIO_REGMAP_QUIRK_SET_AFTER_DIR))
+		gpio_regmap_set(chip, offset, value);
 
-	return gpio_regmap_set_direction(chip, offset, true);
+	ret = gpio_regmap_set_direction(chip, offset, true);
+	if (ret)
+		return ret;
+
+	if (gpio->quirks & GPIO_REGMAP_QUIRK_SET_AFTER_DIR)
+		gpio_regmap_set(chip, offset, value);
+
+	return 0;
 }
 
 void *gpio_regmap_get_drvdata(struct gpio_regmap *gpio)
@@ -376,6 +385,8 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 			    config->fixed_direction_output, chip->ngpio);
 	}
 
+	gpio->quirks = config->quirks;
+
 	/* if not set, assume there is only one register */
 	gpio->ngpio_per_reg = config->ngpio_per_reg;
 	if (!gpio->ngpio_per_reg)
diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
index 06255756710d..f9090073c852 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -3,6 +3,8 @@
 #ifndef _LINUX_GPIO_REGMAP_H
 #define _LINUX_GPIO_REGMAP_H
 
+#include <linux/bits.h>
+
 struct device;
 struct fwnode_handle;
 struct gpio_regmap;
@@ -13,6 +15,14 @@ struct regmap;
 #define GPIO_REGMAP_ADDR_ZERO ((unsigned int)(-1))
 #define GPIO_REGMAP_ADDR(addr) ((addr) ? : GPIO_REGMAP_ADDR_ZERO)
 
+/*
+ * Write the output value after the line is switched to output.
+ * Needed when hardware ignores output writes while the line is an input.
+ * This is a legacy quirk; new hardware must not use it. Direction changes
+ * will glitch.
+ */
+#define GPIO_REGMAP_QUIRK_SET_AFTER_DIR BIT(0)
+
 /**
  * struct gpio_regmap_config - Description of a generic regmap gpio_chip.
  * @parent:		The parent device
@@ -48,6 +58,7 @@ struct regmap;
  *			(Optional) Bitmap representing the fixed direction of
  *			the GPIO lines. Useful when there are GPIO lines with a
  *			fixed direction mixed together in the same register.
+ * @quirks:		(Optional) Behaviour flags, OR of GPIO_REGMAP_QUIRK_*.
  * @drvdata:		(Optional) Pointer to driver specific data which is
  *			not used by gpio-remap but is provided "as is" to the
  *			driver callback(s).
@@ -98,6 +109,9 @@ struct gpio_regmap_config {
 	unsigned long *fixed_direction_mask;
 	unsigned long *fixed_direction_output;
 
+	/* Regmap GPIO behaviour flags */
+	unsigned long quirks;
+
 #ifdef CONFIG_REGMAP_IRQ
 	struct regmap_irq_chip *regmap_irq_chip;
 	int regmap_irq_line;

-- 
2.34.1