gpio: imx-scu: add imx-scu GPIO driver

The SCU firmware on i.MX8 platforms provides a set of APIs to
control the GPIO PINs on the SCU domain. This patch implements the
standard GPIO driver interface to access those PINs on the
SCU domain over the SCU APIs.
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

drivers/gpio/Kconfig

@@ -341,6 +341,10 @@ config GPIO_ICH
 
 	  If unsure, say N.
 
+config GPIO_IMX_SCU
+       def_bool y
+       depends on IMX_SCU
+
 config GPIO_IOP
 	tristate "Intel IOP GPIO"
 	depends on ARCH_IOP32X || COMPILE_TEST

drivers/gpio/Makefile

@@ -70,6 +70,7 @@ obj-$(CONFIG_HTC_EGPIO)			+= gpio-htc-egpio.o
 obj-$(CONFIG_GPIO_I8255)		+= gpio-i8255.o
 obj-$(CONFIG_GPIO_ICH)			+= gpio-ich.o
 obj-$(CONFIG_GPIO_IDT3243X)		+= gpio-idt3243x.o
+obj-$(CONFIG_GPIO_IMX_SCU)		+= gpio-imx-scu.o
 obj-$(CONFIG_GPIO_IOP)			+= gpio-iop.o
 obj-$(CONFIG_GPIO_IT87)			+= gpio-it87.o
 obj-$(CONFIG_GPIO_IXP4XX)		+= gpio-ixp4xx.o

drivers/gpio/gpio-imx-scu.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2021~2022 NXP
+ *
+ * The driver exports a standard gpiochip interface
+ * to control the PIN resources on SCU domain.
+ */
+
+#include <linux/module.h>
+#include <linux/gpio/driver.h>
+#include <linux/platform_device.h>
+#include <linux/firmware/imx/svc/rm.h>
+#include <dt-bindings/firmware/imx/rsrc.h>
+
+struct scu_gpio_priv {
+	struct gpio_chip	chip;
+	struct mutex		lock;
+	struct device		*dev;
+	struct imx_sc_ipc	*handle;
+};
+
+static unsigned int scu_rsrc_arr[] = {
+	IMX_SC_R_BOARD_R0,
+	IMX_SC_R_BOARD_R1,
+	IMX_SC_R_BOARD_R2,
+	IMX_SC_R_BOARD_R3,
+	IMX_SC_R_BOARD_R4,
+	IMX_SC_R_BOARD_R5,
+	IMX_SC_R_BOARD_R6,
+	IMX_SC_R_BOARD_R7,
+};
+
+static int imx_scu_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct scu_gpio_priv *priv = gpiochip_get_data(chip);
+	int level;
+	int err;
+
+	if (offset >= chip->ngpio)
+		return -EINVAL;
+
+	mutex_lock(&priv->lock);
+
+	/* to read PIN state via scu api */
+	err = imx_sc_misc_get_control(priv->handle,
+			scu_rsrc_arr[offset], 0, &level);
+	mutex_unlock(&priv->lock);
+
+	if (err) {
+		dev_err(priv->dev, "SCU get failed: %d\n", err);
+		return err;
+	}
+
+	return level;
+}
+
+static void imx_scu_gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
+{
+	struct scu_gpio_priv *priv = gpiochip_get_data(chip);
+	int err;
+
+	if (offset >= chip->ngpio)
+		return;
+
+	mutex_lock(&priv->lock);
+
+	/* to set PIN output level via scu api */
+	err = imx_sc_misc_set_control(priv->handle,
+			scu_rsrc_arr[offset], 0, value);
+	mutex_unlock(&priv->lock);
+
+	if (err)
+		dev_err(priv->dev, "SCU set (%d) failed: %d\n",
+				scu_rsrc_arr[offset], err);
+}
+
+static int imx_scu_gpio_get_direction(struct gpio_chip *chip, unsigned int offset)
+{
+	if (offset >= chip->ngpio)
+		return -EINVAL;
+
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int imx_scu_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct scu_gpio_priv *priv;
+	struct gpio_chip *gc;
+	int ret;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	ret = imx_scu_get_handle(&priv->handle);
+	if (ret)
+		return ret;
+
+	priv->dev = dev;
+	mutex_init(&priv->lock);
+
+	gc = &priv->chip;
+	gc->base = -1;
+	gc->parent = dev;
+	gc->ngpio = sizeof(scu_rsrc_arr)/sizeof(unsigned int);
+	gc->label = dev_name(dev);
+	gc->get = imx_scu_gpio_get;
+	gc->set = imx_scu_gpio_set;
+	gc->get_direction = imx_scu_gpio_get_direction;
+
+	platform_set_drvdata(pdev, priv);
+
+	return devm_gpiochip_add_data(dev, gc, priv);
+}
+
+static const struct of_device_id imx_scu_gpio_dt_ids[] = {
+	{ .compatible = "fsl,imx8qxp-sc-gpio" },
+	{ /* sentinel */ }
+};
+
+static struct platform_driver imx_scu_gpio_driver = {
+	.driver	= {
+		.name = "gpio-imx-scu",
+		.of_match_table = imx_scu_gpio_dt_ids,
+	},
+	.probe = imx_scu_gpio_probe,
+};
+
+static int __init _imx_scu_gpio_init(void)
+{
+	return platform_driver_register(&imx_scu_gpio_driver);
+}
+
+subsys_initcall_sync(_imx_scu_gpio_init);
+
+MODULE_AUTHOR("Shenwei Wang <shenwei.wang@nxp.com>");
+MODULE_DESCRIPTION("NXP GPIO over IMX SCU API");
+MODULE_LICENSE("GPL");