gpio: Add driver for Nomadik GPIO

Nomadik GPIO is a fairly simple GPIO module used in the ST-Ericsson
Ux500 SoCs (and some older Nomadik SoCs). It uses registers where
each GPIO is represented as a single bit, plus "set" and "clear"
registers that allow updating the state without having to read the
existing state.

The driver implements support for it for use together with DM_GPIO
and the existing ste-dbx5x0.dtsi device tree.

Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -495,4 +495,12 @@ config NX_GPIO
 	  The GPIOs for a device are defined in the device tree with one node
 	  for each bank.
 
+config NOMADIK_GPIO
+	bool "Nomadik GPIO driver"
+	depends on DM_GPIO
+	help
+	  Support GPIO access on ST-Ericsson Ux500 SoCs. The GPIOs are arranged
+	  into a number of banks each with 32 GPIOs. The GPIOs for a device are
+	  defined in the device tree with one node for each bank.
+
 endmenu

drivers/gpio/Makefile

@@ -67,3 +67,4 @@ obj-$(CONFIG_MT7621_GPIO)	+= mt7621_gpio.o
 obj-$(CONFIG_MSCC_SGPIO)	+= mscc_sgpio.o
 obj-$(CONFIG_NX_GPIO)		+= nx_gpio.o
 obj-$(CONFIG_SIFIVE_GPIO)	+= sifive-gpio.o
+obj-$(CONFIG_NOMADIK_GPIO)	+= nmk_gpio.o

drivers/gpio/nmk_gpio.c

@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (C) 2019 Stephan Gerhold */
+
+#include <common.h>
+#include <dm.h>
+#include <asm/gpio.h>
+#include <asm/io.h>
+
+struct nmk_gpio_regs {
+	u32 dat;	/* data */
+	u32 dats;	/* data set */
+	u32 datc;	/* data clear */
+	u32 pdis;	/* pull disable */
+	u32 dir;	/* direction */
+	u32 dirs;	/* direction set */
+	u32 dirc;	/* direction clear */
+	u32 slpm;	/* sleep mode */
+	u32 afsla;	/* alternate function select A */
+	u32 afslb;	/* alternate function select B */
+	u32 lowemi;	/* low EMI mode */
+};
+
+struct nmk_gpio {
+	struct nmk_gpio_regs *regs;
+};
+
+static int nmk_gpio_get_value(struct udevice *dev, unsigned offset)
+{
+	struct nmk_gpio *priv = dev_get_priv(dev);
+
+	return !!(readl(&priv->regs->dat) & BIT(offset));
+}
+
+static int nmk_gpio_set_value(struct udevice *dev, unsigned offset, int value)
+{
+	struct nmk_gpio *priv = dev_get_priv(dev);
+
+	if (value)
+		writel(BIT(offset), &priv->regs->dats);
+	else
+		writel(BIT(offset), &priv->regs->datc);
+
+	return 0;
+}
+
+static int nmk_gpio_get_function(struct udevice *dev, unsigned offset)
+{
+	struct nmk_gpio *priv = dev_get_priv(dev);
+
+	if (readl(&priv->regs->afsla) & BIT(offset) ||
+	    readl(&priv->regs->afslb) & BIT(offset))
+		return GPIOF_FUNC;
+
+	if (readl(&priv->regs->dir) & BIT(offset))
+		return GPIOF_OUTPUT;
+	else
+		return GPIOF_INPUT;
+}
+
+static int nmk_gpio_direction_input(struct udevice *dev, unsigned offset)
+{
+	struct nmk_gpio *priv = dev_get_priv(dev);
+
+	writel(BIT(offset), &priv->regs->dirc);
+	return 0;
+}
+
+static int nmk_gpio_direction_output(struct udevice *dev, unsigned offset,
+				     int value)
+{
+	struct nmk_gpio *priv = dev_get_priv(dev);
+
+	writel(BIT(offset), &priv->regs->dirs);
+	return nmk_gpio_set_value(dev, offset, value);
+}
+
+static const struct dm_gpio_ops nmk_gpio_ops = {
+	.get_value		= nmk_gpio_get_value,
+	.set_value		= nmk_gpio_set_value,
+	.get_function		= nmk_gpio_get_function,
+	.direction_input	= nmk_gpio_direction_input,
+	.direction_output	= nmk_gpio_direction_output,
+};
+
+static int nmk_gpio_probe(struct udevice *dev)
+{
+	struct nmk_gpio *priv = dev_get_priv(dev);
+	struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+	char buf[20];
+	u32 bank;
+	int ret;
+
+	priv->regs = dev_read_addr_ptr(dev);
+	if (!priv->regs)
+		return -EINVAL;
+
+	ret = dev_read_u32(dev, "gpio-bank", &bank);
+	if (ret < 0) {
+		printf("nmk_gpio(%s): Failed to read gpio-bank\n", dev->name);
+		return ret;
+	}
+
+	sprintf(buf, "nmk%u-gpio", bank);
+	uc_priv->bank_name = strdup(buf);
+	if (!uc_priv->bank_name)
+		return -ENOMEM;
+
+	uc_priv->gpio_count = sizeof(priv->regs->dat) * BITS_PER_BYTE;
+
+	return 0;
+}
+
+static const struct udevice_id nmk_gpio_ids[] = {
+	{ .compatible = "st,nomadik-gpio" },
+	{ }
+};
+
+U_BOOT_DRIVER(gpio_nmk) = {
+	.name		= "nmk_gpio",
+	.id		= UCLASS_GPIO,
+	.of_match	= nmk_gpio_ids,
+	.probe		= nmk_gpio_probe,
+	.ops		= &nmk_gpio_ops,
+	.priv_auto	= sizeof(struct nmk_gpio),
+};