rtc: ds2404: Convert to GPIO descriptors

This converts the DS2404 to use GPIO descriptors instead of
hard-coded global GPIO numbers.

The platform data can be deleted because there are no in-tree
users and it only contained GPIO numbers which are now
passed using descriptor tables (or device tree or ACPI).

The driver was rewritten to use a state container for the
device driver state (struct ds2404 *chip) and pass that
around instead of using a global singleton storage for the
GPIO handles.

When declaring GPIO descriptor tables or other hardware
descriptions for the RTC driver, implementers should take care
to flag the RESET line as active low, such as by using the
GPIOD_ACTIVE_LOW flag in the descriptor table.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230807-descriptors-rtc-v1-1-ce0f9187576e@linaro.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: Linus Walleij

drivers/rtc/rtc-ds2404.c

@@ -7,9 +7,8 @@
 #include <linux/rtc.h>
 #include <linux/types.h>
 #include <linux/bcd.h>
-#include <linux/platform_data/rtc-ds2404.h>
 #include <linux/delay.h>
-#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/slab.h>
 
 #include <linux/io.h>
@@ -27,164 +26,140 @@
 #define DS2404_CLK	1
 #define DS2404_DQ	2
 
-struct ds2404_gpio {
-	const char *name;
-	unsigned int gpio;
-};
-
 struct ds2404 {
-	struct ds2404_gpio *gpio;
+	struct device *dev;
+	struct gpio_desc *rst_gpiod;
+	struct gpio_desc *clk_gpiod;
+	struct gpio_desc *dq_gpiod;
 	struct rtc_device *rtc;
 };
 
-static struct ds2404_gpio ds2404_gpio[] = {
-	{ "RTC RST", 0 },
-	{ "RTC CLK", 0 },
-	{ "RTC DQ", 0 },
-};
-
-static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev,
-			  struct ds2404_platform_data *pdata)
+static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev)
 {
-	int i, err;
-
-	ds2404_gpio[DS2404_RST].gpio = pdata->gpio_rst;
-	ds2404_gpio[DS2404_CLK].gpio = pdata->gpio_clk;
-	ds2404_gpio[DS2404_DQ].gpio = pdata->gpio_dq;
-
-	for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++) {
-		err = gpio_request(ds2404_gpio[i].gpio, ds2404_gpio[i].name);
-		if (err) {
-			dev_err(&pdev->dev, "error mapping gpio %s: %d\n",
-				ds2404_gpio[i].name, err);
-			goto err_request;
-		}
-		if (i != DS2404_DQ)
-			gpio_direction_output(ds2404_gpio[i].gpio, 1);
-	}
+	struct device *dev = &pdev->dev;
 
-	chip->gpio = ds2404_gpio;
-	return 0;
+	/* This will de-assert RESET, declare this GPIO as GPIOD_ACTIVE_LOW */
+	chip->rst_gpiod = devm_gpiod_get(dev, "rst", GPIOD_OUT_LOW);
+	if (IS_ERR(chip->rst_gpiod))
+		return PTR_ERR(chip->rst_gpiod);
 
-err_request:
-	while (--i >= 0)
-		gpio_free(ds2404_gpio[i].gpio);
-	return err;
-}
+	chip->clk_gpiod = devm_gpiod_get(dev, "clk", GPIOD_OUT_HIGH);
+	if (IS_ERR(chip->clk_gpiod))
+		return PTR_ERR(chip->clk_gpiod);
 
-static void ds2404_gpio_unmap(void *data)
-{
-	int i;
+	chip->dq_gpiod = devm_gpiod_get(dev, "dq", GPIOD_ASIS);
+	if (IS_ERR(chip->dq_gpiod))
+		return PTR_ERR(chip->dq_gpiod);
 
-	for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++)
-		gpio_free(ds2404_gpio[i].gpio);
+	return 0;
 }
 
-static void ds2404_reset(struct device *dev)
+static void ds2404_reset(struct ds2404 *chip)
 {
-	gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 0);
+	gpiod_set_value(chip->rst_gpiod, 1);
 	udelay(1000);
-	gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 1);
-	gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
-	gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 0);
+	gpiod_set_value(chip->rst_gpiod, 0);
+	gpiod_set_value(chip->clk_gpiod, 0);
+	gpiod_direction_output(chip->dq_gpiod, 0);
 	udelay(10);
 }
 
-static void ds2404_write_byte(struct device *dev, u8 byte)
+static void ds2404_write_byte(struct ds2404 *chip, u8 byte)
 {
 	int i;
 
-	gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 1);
+	gpiod_direction_output(chip->dq_gpiod, 1);
 	for (i = 0; i < 8; i++) {
-		gpio_set_value(ds2404_gpio[DS2404_DQ].gpio, byte & (1 << i));
+		gpiod_set_value(chip->dq_gpiod, byte & (1 << i));
 		udelay(10);
-		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
+		gpiod_set_value(chip->clk_gpiod, 1);
 		udelay(10);
-		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
+		gpiod_set_value(chip->clk_gpiod, 0);
 		udelay(10);
 	}
 }
 
-static u8 ds2404_read_byte(struct device *dev)
+static u8 ds2404_read_byte(struct ds2404 *chip)
 {
 	int i;
 	u8 ret = 0;
 
-	gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
+	gpiod_direction_input(chip->dq_gpiod);
 
 	for (i = 0; i < 8; i++) {
-		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
+		gpiod_set_value(chip->clk_gpiod, 0);
 		udelay(10);
-		if (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
+		if (gpiod_get_value(chip->dq_gpiod))
 			ret |= 1 << i;
-		gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
+		gpiod_set_value(chip->clk_gpiod, 1);
 		udelay(10);
 	}
 	return ret;
 }
 
-static void ds2404_read_memory(struct device *dev, u16 offset,
+static void ds2404_read_memory(struct ds2404 *chip, u16 offset,
 			       int length, u8 *out)
 {
-	ds2404_reset(dev);
-	ds2404_write_byte(dev, DS2404_READ_MEMORY_CMD);
-	ds2404_write_byte(dev, offset & 0xff);
-	ds2404_write_byte(dev, (offset >> 8) & 0xff);
+	ds2404_reset(chip);
+	ds2404_write_byte(chip, DS2404_READ_MEMORY_CMD);
+	ds2404_write_byte(chip, offset & 0xff);
+	ds2404_write_byte(chip, (offset >> 8) & 0xff);
 	while (length--)
-		*out++ = ds2404_read_byte(dev);
+		*out++ = ds2404_read_byte(chip);
 }
 
-static void ds2404_write_memory(struct device *dev, u16 offset,
+static void ds2404_write_memory(struct ds2404 *chip, u16 offset,
 				int length, u8 *out)
 {
 	int i;
 	u8 ta01, ta02, es;
 
-	ds2404_reset(dev);
-	ds2404_write_byte(dev, DS2404_WRITE_SCRATCHPAD_CMD);
-	ds2404_write_byte(dev, offset & 0xff);
-	ds2404_write_byte(dev, (offset >> 8) & 0xff);
+	ds2404_reset(chip);
+	ds2404_write_byte(chip, DS2404_WRITE_SCRATCHPAD_CMD);
+	ds2404_write_byte(chip, offset & 0xff);
+	ds2404_write_byte(chip, (offset >> 8) & 0xff);
 
 	for (i = 0; i < length; i++)
-		ds2404_write_byte(dev, out[i]);
+		ds2404_write_byte(chip, out[i]);
 
-	ds2404_reset(dev);
-	ds2404_write_byte(dev, DS2404_READ_SCRATCHPAD_CMD);
+	ds2404_reset(chip);
+	ds2404_write_byte(chip, DS2404_READ_SCRATCHPAD_CMD);
 
-	ta01 = ds2404_read_byte(dev);
-	ta02 = ds2404_read_byte(dev);
-	es = ds2404_read_byte(dev);
+	ta01 = ds2404_read_byte(chip);
+	ta02 = ds2404_read_byte(chip);
+	es = ds2404_read_byte(chip);
 
 	for (i = 0; i < length; i++) {
-		if (out[i] != ds2404_read_byte(dev)) {
-			dev_err(dev, "read invalid data\n");
+		if (out[i] != ds2404_read_byte(chip)) {
+			dev_err(chip->dev, "read invalid data\n");
 			return;
 		}
 	}
 
-	ds2404_reset(dev);
-	ds2404_write_byte(dev, DS2404_COPY_SCRATCHPAD_CMD);
-	ds2404_write_byte(dev, ta01);
-	ds2404_write_byte(dev, ta02);
-	ds2404_write_byte(dev, es);
+	ds2404_reset(chip);
+	ds2404_write_byte(chip, DS2404_COPY_SCRATCHPAD_CMD);
+	ds2404_write_byte(chip, ta01);
+	ds2404_write_byte(chip, ta02);
+	ds2404_write_byte(chip, es);
 
-	gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
-	while (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
+	while (gpiod_get_value(chip->dq_gpiod))
 		;
 }
 
-static void ds2404_enable_osc(struct device *dev)
+static void ds2404_enable_osc(struct ds2404 *chip)
 {
 	u8 in[1] = { 0x10 }; /* enable oscillator */
-	ds2404_write_memory(dev, 0x201, 1, in);
+
+	ds2404_write_memory(chip, 0x201, 1, in);
 }
 
 static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
 {
+	struct ds2404 *chip = dev_get_drvdata(dev);
 	unsigned long time = 0;
 	__le32 hw_time = 0;
 
-	ds2404_read_memory(dev, 0x203, 4, (u8 *)&hw_time);
+	ds2404_read_memory(chip, 0x203, 4, (u8 *)&hw_time);
 	time = le32_to_cpu(hw_time);
 
 	rtc_time64_to_tm(time, dt);
@@ -193,8 +168,9 @@ static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
 
 static int ds2404_set_time(struct device *dev, struct rtc_time *dt)
 {
+	struct ds2404 *chip = dev_get_drvdata(dev);
 	u32 time = cpu_to_le32(rtc_tm_to_time64(dt));
-	ds2404_write_memory(dev, 0x203, 4, (u8 *)&time);
+	ds2404_write_memory(chip, 0x203, 4, (u8 *)&time);
 	return 0;
 }
 
@@ -205,30 +181,23 @@ static const struct rtc_class_ops ds2404_rtc_ops = {
 
 static int rtc_probe(struct platform_device *pdev)
 {
-	struct ds2404_platform_data *pdata = dev_get_platdata(&pdev->dev);
 	struct ds2404 *chip;
 	int retval = -EBUSY;
 
 	chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL);
 	if (!chip)
 		return -ENOMEM;
 
+	chip->dev = &pdev->dev;
+
 	chip->rtc = devm_rtc_allocate_device(&pdev->dev);
 	if (IS_ERR(chip->rtc))
 		return PTR_ERR(chip->rtc);
 
-	retval = ds2404_gpio_map(chip, pdev, pdata);
+	retval = ds2404_gpio_map(chip, pdev);
 	if (retval)
 		return retval;
 
-	retval = devm_add_action_or_reset(&pdev->dev, ds2404_gpio_unmap, chip);
-	if (retval)
-		return retval;
-
-	dev_info(&pdev->dev, "using GPIOs RST:%d, CLK:%d, DQ:%d\n",
-		 chip->gpio[DS2404_RST].gpio, chip->gpio[DS2404_CLK].gpio,
-		 chip->gpio[DS2404_DQ].gpio);
-
 	platform_set_drvdata(pdev, chip);
 
 	chip->rtc->ops = &ds2404_rtc_ops;
@@ -238,7 +207,7 @@ static int rtc_probe(struct platform_device *pdev)
 	if (retval)
 		return retval;
 
-	ds2404_enable_osc(&pdev->dev);
+	ds2404_enable_osc(chip);
 	return 0;
 }