[PATCH] gpio: pca953x: Add GPIO settle delay

[Judith Mendez <jm@ti.com>]

Some board designs have slow RC circuits on GPIO outputs controlled by
PCA953X I2C expanders. On some board designs, pin voltage transitions
can take significant time after I2C write command completes.

Add an optional "gpio-settle-delay-ms" device tree property for the
pca953x driver to add a delay after I2C write if specified, allowing to
compensate for slow RC circuits.

Signed-off-by: Judith Mendez <jm@ti.com>
---
 drivers/gpio/pca953x_gpio.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpio/pca953x_gpio.c b/drivers/gpio/pca953x_gpio.c
index 965a5fcf30b..54b957069c9 100644
--- a/drivers/gpio/pca953x_gpio.c
+++ b/drivers/gpio/pca953x_gpio.c
@@ -28,6 +28,7 @@
 #include <dm/device_compat.h>
 #include <dt-bindings/gpio/gpio.h>
 #include <linux/bitops.h>
+#include <linux/delay.h>
 
 #define PCA953X_INPUT           0
 #define PCA953X_OUTPUT          1
@@ -89,6 +90,7 @@ static const struct pca95xx_reg pca957x_regs = {
  * @reg_output: array to hold the value of output registers
  * @reg_direction: array to hold the value of direction registers
  * @regs: struct to hold the registers addresses
+ * @settle_delay_ms: GPIO pin settle delay in milliseconds
  */
 struct pca953x_info {
 	struct udevice *dev;
@@ -100,6 +102,7 @@ struct pca953x_info {
 	u8 reg_output[MAX_BANK];
 	u8 reg_direction[MAX_BANK];
 	const struct pca95xx_reg *regs;
+	u32 settle_delay_ms;
 };
 
 static int pca953x_write_single(struct udevice *dev, int reg, u8 val,
@@ -116,6 +119,9 @@ static int pca953x_write_single(struct udevice *dev, int reg, u8 val,
 		return ret;
 	}
 
+	if (info->settle_delay_ms)
+		mdelay(info->settle_delay_ms);
+
 	return 0;
 }
 
@@ -333,6 +339,8 @@ static int pca953x_probe(struct udevice *dev)
 
 	info->bank_count = DIV_ROUND_UP(info->gpio_count, BANK_SZ);
 
+	info->settle_delay_ms = dev_read_u32_default(dev, "gpio-settle-delay-ms", 0);
+
 	ret = pca953x_read_regs(dev, info->regs->output, info->reg_output);
 	if (ret) {
 		dev_err(dev, "Error reading output register\n");
-- 
2.54.0