linux-kernel - [PATCH 2/2] mux: gpio: Support settle-time-us property

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Date:   Mon, 4 Oct 2021 17:36:40 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     <peda@...ntia.se>, <devicetree@...r.kernel.org>
CC:     <kernel@...s.com>, <robh+dt@...nel.org>,
        <linux-kernel@...r.kernel.org>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>
Subject: [PATCH 2/2] mux: gpio: Support settle-time-us property

If the devicetree specifies that the hardware requires a settle time,
add an appropriate delay after the mux GPIOs are set.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 drivers/mux/gpio.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/mux/gpio.c b/drivers/mux/gpio.c
index cc5f2c1861d4..17d7e03e39f0 100644
--- a/drivers/mux/gpio.c
+++ b/drivers/mux/gpio.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/bitmap.h>
+#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/gpio/consumer.h>
 #include <linux/mod_devicetable.h>
@@ -18,12 +19,14 @@
 
 struct mux_gpio {
 	struct gpio_descs *gpios;
+	u32 delay;
 };
 
 static int mux_gpio_set(struct mux_control *mux, int state)
 {
 	struct mux_gpio *mux_gpio = mux_chip_priv(mux->chip);
 	DECLARE_BITMAP(values, BITS_PER_TYPE(state));
+	u32 delay = mux_gpio->delay;
 	u32 value = state;
 
 	bitmap_from_arr32(values, &value, BITS_PER_TYPE(value));
@@ -32,6 +35,9 @@ static int mux_gpio_set(struct mux_control *mux, int state)
 				       mux_gpio->gpios->desc,
 				       mux_gpio->gpios->info, values);
 
+	if (delay)
+		fsleep(delay);
+
 	return 0;
 }
 
@@ -72,6 +78,9 @@ static int mux_gpio_probe(struct platform_device *pdev)
 	WARN_ON(pins != mux_gpio->gpios->ndescs);
 	mux_chip->mux->states = BIT(pins);
 
+	mux_gpio->delay = 0;
+	device_property_read_u32(dev, "settle-time-us", &mux_gpio->delay);
+
 	ret = device_property_read_u32(dev, "idle-state", (u32 *)&idle_state);
 	if (ret >= 0 && idle_state != MUX_IDLE_AS_IS) {
 		if (idle_state < 0 || idle_state >= mux_chip->mux->states) {
-- 
2.28.0