[PATCH v8 08/18] gpiolib: regmap: add write_data_after_dir quirk

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

From: Long Zhao <longzhao@ambarella.com>

Some controllers ignore data-register writes while a line is still an
input. Optionally write the output value again after switching the
direction, matching the existing PL061 behaviour.

Signed-off-by: Long Zhao <longzhao@ambarella.com>
---
 drivers/gpio/gpio-regmap.c  | 19 +++++++++++++++++--
 include/linux/gpio/regmap.h |  8 ++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index 51b4d69b8740..fbd4c753525a 100644
--- a/drivers/gpio/gpio-regmap.c
+++ b/drivers/gpio/gpio-regmap.c
@@ -31,6 +31,7 @@ struct gpio_regmap {
 	unsigned int reg_clr_base;
 	unsigned int reg_dir_in_base;
 	unsigned int reg_dir_out_base;
+	bool write_data_after_dir;
 	unsigned long *fixed_direction_mask;
 	unsigned long *fixed_direction_output;
 
@@ -271,9 +272,21 @@ static int gpio_regmap_direction_output(struct gpio_chip *chip,
 			return ret;
 	}
 
-	gpio_regmap_set(chip, offset, value);
+	if (!gpio->write_data_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;
+
+	/*
+	 * Some controllers ignore data-register writes while the line is
+	 * still an input. Write the output value after switching direction.
+	 */
+	if (gpio->write_data_after_dir)
+		gpio_regmap_set(chip, offset, value);
+
+	return 0;
 }
 
 void *gpio_regmap_get_drvdata(struct gpio_regmap *gpio)
@@ -376,6 +389,8 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 			    config->fixed_direction_output, chip->ngpio);
 	}
 
+	gpio->write_data_after_dir = config->write_data_after_dir;
+
 	/* 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..d7ffc12b00a2 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -48,6 +48,13 @@ 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.
+ * @write_data_after_dir:
+ *			(Optional) Write the output value again after
+ *			switching a line to output in ->direction_output().
+ *			Needed for hardware which ignores data register
+ *			writes while the line is configured as an input.
+ *			This is a legacy quirk (e.g. ARM PL061); new hardware
+ *			must not use it. Direction changes will glitch.
  * @drvdata:		(Optional) Pointer to driver specific data which is
  *			not used by gpio-remap but is provided "as is" to the
  *			driver callback(s).
@@ -94,6 +101,7 @@ struct gpio_regmap_config {
 	unsigned int reg_dir_out_base;
 	int reg_stride;
 	int ngpio_per_reg;
+	bool write_data_after_dir;
 	struct irq_domain *irq_domain;
 	unsigned long *fixed_direction_mask;
 	unsigned long *fixed_direction_output;

-- 
2.34.1