gpio: Support ROHM BD71815 GPOs

Support GPO(s) found from ROHM BD71815 power management IC. The IC has two
GPO pins but only one is properly documented in the data-sheet. The driver
exposes by default only the documented GPO. The second GPO is connected to
E5 pin and is marked as GND in the data-sheet. Control for this
undocumented pin can be enabled using a special DT property.

This driver is derived from work by Peter Yang <yanglsh@embest-tech.com>
although not so much of the original is left.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/gpio/Kconfig

@@ -1105,6 +1105,16 @@ config GPIO_BD70528
 	  This driver can also be built as a module. If so, the module
 	  will be called gpio-bd70528.
 
+config GPIO_BD71815
+	tristate "ROHM BD71815 PMIC GPIO support"
+	depends on MFD_ROHM_BD71828
+	help
+	  Support for GPO(s) on ROHM BD71815 PMIC. There are two GPOs
+	  available on the ROHM PMIC.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called gpio-bd71815.
+
 config GPIO_BD71828
 	tristate "ROHM BD71828 GPIO support"
 	depends on MFD_ROHM_BD71828

drivers/gpio/Makefile

@@ -39,6 +39,7 @@ obj-$(CONFIG_GPIO_ATH79)		+= gpio-ath79.o
 obj-$(CONFIG_GPIO_BCM_KONA)		+= gpio-bcm-kona.o
 obj-$(CONFIG_GPIO_BCM_XGS_IPROC)	+= gpio-xgs-iproc.o
 obj-$(CONFIG_GPIO_BD70528)		+= gpio-bd70528.o
+obj-$(CONFIG_GPIO_BD71815)		+= gpio-bd71815.o
 obj-$(CONFIG_GPIO_BD71828)		+= gpio-bd71828.o
 obj-$(CONFIG_GPIO_BD9571MWV)		+= gpio-bd9571mwv.o
 obj-$(CONFIG_GPIO_BRCMSTB)		+= gpio-brcmstb.o

drivers/gpio/gpio-bd71815.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support to GPOs on ROHM BD71815
+ * Copyright 2021 ROHM Semiconductors.
+ * Author: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
+ *
+ * Copyright 2014 Embest Technology Co. Ltd. Inc.
+ * Author: yanglsh@embest-tech.com
+ */
+
+#include <linux/gpio/driver.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+/* For the BD71815 register definitions */
+#include <linux/mfd/rohm-bd71815.h>
+
+struct bd71815_gpio {
+	/* chip.parent points the MFD which provides DT node and regmap */
+	struct gpio_chip chip;
+	/* dev points to the platform device for devm and prints */
+	struct device *dev;
+	struct regmap *regmap;
+};
+
+static int bd71815gpo_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct bd71815_gpio *bd71815 = gpiochip_get_data(chip);
+	int ret, val;
+
+	ret = regmap_read(bd71815->regmap, BD71815_REG_GPO, &val);
+	if (ret)
+		return ret;
+
+	return (val >> offset) & 1;
+}
+
+static void bd71815gpo_set(struct gpio_chip *chip, unsigned int offset,
+			   int value)
+{
+	struct bd71815_gpio *bd71815 = gpiochip_get_data(chip);
+	int ret, bit;
+
+	bit = BIT(offset);
+
+	if (value)
+		ret = regmap_set_bits(bd71815->regmap, BD71815_REG_GPO, bit);
+	else
+		ret = regmap_clear_bits(bd71815->regmap, BD71815_REG_GPO, bit);
+
+	if (ret)
+		dev_warn(bd71815->dev, "failed to toggle GPO\n");
+}
+
+static int bd71815_gpio_set_config(struct gpio_chip *chip, unsigned int offset,
+				   unsigned long config)
+{
+	struct bd71815_gpio *bdgpio = gpiochip_get_data(chip);
+
+	switch (pinconf_to_config_param(config)) {
+	case PIN_CONFIG_DRIVE_OPEN_DRAIN:
+		return regmap_update_bits(bdgpio->regmap,
+					  BD71815_REG_GPO,
+					  BD71815_GPIO_DRIVE_MASK << offset,
+					  BD71815_GPIO_OPEN_DRAIN << offset);
+	case PIN_CONFIG_DRIVE_PUSH_PULL:
+		return regmap_update_bits(bdgpio->regmap,
+					  BD71815_REG_GPO,
+					  BD71815_GPIO_DRIVE_MASK << offset,
+					  BD71815_GPIO_CMOS << offset);
+	default:
+		break;
+	}
+	return -ENOTSUPP;
+}
+
+/* BD71815 GPIO is actually GPO */
+static int bd71815gpo_direction_get(struct gpio_chip *gc, unsigned int offset)
+{
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+/* Template for GPIO chip */
+static const struct gpio_chip bd71815gpo_chip = {
+	.label			= "bd71815",
+	.owner			= THIS_MODULE,
+	.get			= bd71815gpo_get,
+	.get_direction		= bd71815gpo_direction_get,
+	.set			= bd71815gpo_set,
+	.set_config		= bd71815_gpio_set_config,
+	.can_sleep		= true,
+};
+
+#define BD71815_TWO_GPIOS	GENMASK(1, 0)
+#define BD71815_ONE_GPIO	BIT(0)
+
+/*
+ * Sigh. The BD71815 and BD71817 were originally designed to support two GPO
+ * pins. At some point it was noticed the second GPO pin which is the E5 pin
+ * located at the center of IC is hard to use on PCB (due to the location). It
+ * was decided to not promote this second GPO and the pin is marked as GND in
+ * the datasheet. The functionality is still there though! I guess driving a GPO
+ * connected to the ground is a bad idea. Thus we do not support it by default.
+ * OTOH - the original driver written by colleagues at Embest did support
+ * controlling this second GPO. It is thus possible this is used in some of the
+ * products.
+ *
+ * This driver does not by default support configuring this second GPO
+ * but allows using it by providing the DT property
+ * "rohm,enable-hidden-gpo".
+ */
+static int bd71815_init_valid_mask(struct gpio_chip *gc,
+				   unsigned long *valid_mask,
+				   unsigned int ngpios)
+{
+	if (ngpios != 2)
+		return 0;
+
+	if (gc->parent && device_property_present(gc->parent,
+						  "rohm,enable-hidden-gpo"))
+		*valid_mask = BD71815_TWO_GPIOS;
+	else
+		*valid_mask = BD71815_ONE_GPIO;
+
+	return 0;
+}
+
+static int gpo_bd71815_probe(struct platform_device *pdev)
+{
+	struct bd71815_gpio *g;
+	struct device *parent, *dev;
+
+	/*
+	 * Bind devm lifetime to this platform device => use dev for devm.
+	 * also the prints should originate from this device.
+	 */
+	dev = &pdev->dev;
+	/* The device-tree and regmap come from MFD => use parent for that */
+	parent = dev->parent;
+
+	g = devm_kzalloc(dev, sizeof(*g), GFP_KERNEL);
+	if (!g)
+		return -ENOMEM;
+
+	g->chip = bd71815gpo_chip;
+
+	/*
+	 * FIXME: As writing of this the sysfs interface for GPIO control does
+	 * not respect the valid_mask. Do not trust it but rather set the ngpios
+	 * to 1 if "rohm,enable-hidden-gpo" is not given.
+	 *
+	 * This check can be removed later if the sysfs export is fixed and
+	 * if the fix is backported.
+	 *
+	 * For now it is safest to just set the ngpios though.
+	 */
+	if (device_property_present(parent, "rohm,enable-hidden-gpo"))
+		g->chip.ngpio = 2;
+	else
+		g->chip.ngpio = 1;
+
+	g->chip.init_valid_mask = bd71815_init_valid_mask;
+	g->chip.base = -1;
+	g->chip.parent = parent;
+	g->regmap = dev_get_regmap(parent, NULL);
+	g->dev = dev;
+
+	return devm_gpiochip_add_data(dev, &g->chip, g);
+}
+
+static struct platform_driver gpo_bd71815_driver = {
+	.driver = {
+		.name	= "bd71815-gpo",
+	},
+	.probe		= gpo_bd71815_probe,
+};
+module_platform_driver(gpo_bd71815_driver);
+
+MODULE_ALIAS("platform:bd71815-gpo");
+MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>");
+MODULE_AUTHOR("Peter Yang <yanglsh@embest-tech.com>");
+MODULE_DESCRIPTION("GPO interface for BD71815");
+MODULE_LICENSE("GPL");