gpio: Add Realtek Otto GPIO support

Realtek MIPS SoCs (platform name Otto) have GPIO controllers with up to
64 GPIOs, divided over two banks. Each bank has a set of registers for
32 GPIOs, with support for edge-triggered interrupts.

Each GPIO bank consists of four 8-bit GPIO ports (ABCD and EFGH). Most
registers pack one bit per GPIO, except for the IMR register, which
packs two bits per GPIO (AB-CD).

Although the byte order is currently assumed to have port A..D at offset
0x0..0x3, this has been observed to be reversed on other, Lexra-based,
SoCs (e.g. RTL8196E/97D/97F).

Interrupt support is disabled for the fallback devicetree-compatible
'realtek,otto-gpio'. This allows for quick support of GPIO banks in
which the byte order would be unknown. In this case, the port ordering
in the IMR registers may not match the reversed order in the other
registers (DCBA, and BA-DC or DC-BA).

Signed-off-by: Sander Vanheule <[e-mail]>
Reviewed-by: Linus Walleij <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/Kconfig

···
 	help
 	  Say Y here to support RDA Micro GPIO controller.
 
+config GPIO_REALTEK_OTTO
+	tristate "Realtek Otto GPIO support"
+	depends on MACH_REALTEK_RTL
+	default MACH_REALTEK_RTL
+	select GPIO_GENERIC
+	select GPIOLIB_IRQCHIP
+	help
+	  The GPIO controller on the Otto MIPS platform supports up to two
+	  banks of 32 GPIOs, with edge triggered interrupts. The 32 GPIOs
+	  are grouped in four 8-bit wide ports.
+
+	  When built as a module, the module will be called realtek_otto_gpio.
+
 config GPIO_REG
 	bool
 	help

drivers/gpio/Makefile

···
 obj-$(CONFIG_GPIO_RCAR)			+= gpio-rcar.o
 obj-$(CONFIG_GPIO_RDA)			+= gpio-rda.o
 obj-$(CONFIG_GPIO_RDC321X)		+= gpio-rdc321x.o
+obj-$(CONFIG_GPIO_REALTEK_OTTO)		+= gpio-realtek-otto.o
 obj-$(CONFIG_GPIO_REG)			+= gpio-reg.o
 obj-$(CONFIG_ARCH_SA1100)		+= gpio-sa1100.o
 obj-$(CONFIG_GPIO_SAMA5D2_PIOBU)	+= gpio-sama5d2-piobu.o

drivers/gpio/gpio-realtek-otto.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/gpio/driver.h>
+#include <linux/irq.h>
+#include <linux/minmax.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+/*
+ * Total register block size is 0x1C for one bank of four ports (A, B, C, D).
+ * An optional second bank, with ports E, F, G, and H, may be present, starting
+ * at register offset 0x1C.
+ */
+
+/*
+ * Pin select: (0) "normal", (1) "dedicate peripheral"
+ * Not used on RTL8380/RTL8390, peripheral selection is managed by control bits
+ * in the peripheral registers.
+ */
+#define REALTEK_GPIO_REG_CNR		0x00
+/* Clear bit (0) for input, set bit (1) for output */
+#define REALTEK_GPIO_REG_DIR		0x08
+#define REALTEK_GPIO_REG_DATA		0x0C
+/* Read bit for IRQ status, write 1 to clear IRQ */
+#define REALTEK_GPIO_REG_ISR		0x10
+/* Two bits per GPIO in IMR registers */
+#define REALTEK_GPIO_REG_IMR		0x14
+#define REALTEK_GPIO_REG_IMR_AB		0x14
+#define REALTEK_GPIO_REG_IMR_CD		0x18
+#define REALTEK_GPIO_IMR_LINE_MASK	GENMASK(1, 0)
+#define REALTEK_GPIO_IRQ_EDGE_FALLING	1
+#define REALTEK_GPIO_IRQ_EDGE_RISING	2
+#define REALTEK_GPIO_IRQ_EDGE_BOTH	3
+
+#define REALTEK_GPIO_MAX		32
+#define REALTEK_GPIO_PORTS_PER_BANK	4
+
+/**
+ * realtek_gpio_ctrl - Realtek Otto GPIO driver data
+ *
+ * @gc: Associated gpio_chip instance
+ * @base: Base address of the register block for a GPIO bank
+ * @lock: Lock for accessing the IRQ registers and values
+ * @intr_mask: Mask for interrupts lines
+ * @intr_type: Interrupt type selection
+ *
+ * Because the interrupt mask register (IMR) combines the function of IRQ type
+ * selection and masking, two extra values are stored. @intr_mask is used to
+ * mask/unmask the interrupts for a GPIO port, and @intr_type is used to store
+ * the selected interrupt types. The logical AND of these values is written to
+ * IMR on changes.
+ */
+struct realtek_gpio_ctrl {
+	struct gpio_chip gc;
+	void __iomem *base;
+	raw_spinlock_t lock;
+	u16 intr_mask[REALTEK_GPIO_PORTS_PER_BANK];
+	u16 intr_type[REALTEK_GPIO_PORTS_PER_BANK];
+};
+
+/* Expand with more flags as devices with other quirks are added */
+enum realtek_gpio_flags {
+	/*
+	 * Allow disabling interrupts, for cases where the port order is
+	 * unknown. This may result in a port mismatch between ISR and IMR.
+	 * An interrupt would appear to come from a different line than the
+	 * line the IRQ handler was assigned to, causing uncaught interrupts.
+	 */
+	GPIO_INTERRUPTS_DISABLED = BIT(0),
+};
+
+static struct realtek_gpio_ctrl *irq_data_to_ctrl(struct irq_data *data)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(data);
+
+	return container_of(gc, struct realtek_gpio_ctrl, gc);
+}
+
+/*
+ * Normal port order register access
+ *
+ * Port information is stored with the first port at offset 0, followed by the
+ * second, etc. Most registers store one bit per GPIO and use a u8 value per
+ * port. The two interrupt mask registers store two bits per GPIO, so use u16
+ * values.
+ */
+static void realtek_gpio_write_imr(struct realtek_gpio_ctrl *ctrl,
+	unsigned int port, u16 irq_type, u16 irq_mask)
+{
+	iowrite16(irq_type & irq_mask, ctrl->base + REALTEK_GPIO_REG_IMR + 2 * port);
+}
+
+static void realtek_gpio_clear_isr(struct realtek_gpio_ctrl *ctrl,
+	unsigned int port, u8 mask)
+{
+	iowrite8(mask, ctrl->base + REALTEK_GPIO_REG_ISR + port);
+}
+
+static u8 realtek_gpio_read_isr(struct realtek_gpio_ctrl *ctrl, unsigned int port)
+{
+	return ioread8(ctrl->base + REALTEK_GPIO_REG_ISR + port);
+}
+
+/* Set the rising and falling edge mask bits for a GPIO port pin */
+static u16 realtek_gpio_imr_bits(unsigned int pin, u16 value)
+{
+	return (value & REALTEK_GPIO_IMR_LINE_MASK) << 2 * pin;
+}
+
+static void realtek_gpio_irq_ack(struct irq_data *data)
+{
+	struct realtek_gpio_ctrl *ctrl = irq_data_to_ctrl(data);
+	irq_hw_number_t line = irqd_to_hwirq(data);
+	unsigned int port = line / 8;
+	unsigned int port_pin = line % 8;
+
+	realtek_gpio_clear_isr(ctrl, port, BIT(port_pin));
+}
+
+static void realtek_gpio_irq_unmask(struct irq_data *data)
+{
+	struct realtek_gpio_ctrl *ctrl = irq_data_to_ctrl(data);
+	unsigned int line = irqd_to_hwirq(data);
+	unsigned int port = line / 8;
+	unsigned int port_pin = line % 8;
+	unsigned long flags;
+	u16 m;
+
+	raw_spin_lock_irqsave(&ctrl->lock, flags);
+	m = ctrl->intr_mask[port];
+	m |= realtek_gpio_imr_bits(port_pin, REALTEK_GPIO_IMR_LINE_MASK);
+	ctrl->intr_mask[port] = m;
+	realtek_gpio_write_imr(ctrl, port, ctrl->intr_type[port], m);
+	raw_spin_unlock_irqrestore(&ctrl->lock, flags);
+}
+
+static void realtek_gpio_irq_mask(struct irq_data *data)
+{
+	struct realtek_gpio_ctrl *ctrl = irq_data_to_ctrl(data);
+	unsigned int line = irqd_to_hwirq(data);
+	unsigned int port = line / 8;
+	unsigned int port_pin = line % 8;
+	unsigned long flags;
+	u16 m;
+
+	raw_spin_lock_irqsave(&ctrl->lock, flags);
+	m = ctrl->intr_mask[port];
+	m &= ~realtek_gpio_imr_bits(port_pin, REALTEK_GPIO_IMR_LINE_MASK);
+	ctrl->intr_mask[port] = m;
+	realtek_gpio_write_imr(ctrl, port, ctrl->intr_type[port], m);
+	raw_spin_unlock_irqrestore(&ctrl->lock, flags);
+}
+
+static int realtek_gpio_irq_set_type(struct irq_data *data, unsigned int flow_type)
+{
+	struct realtek_gpio_ctrl *ctrl = irq_data_to_ctrl(data);
+	unsigned int line = irqd_to_hwirq(data);
+	unsigned int port = line / 8;
+	unsigned int port_pin = line % 8;
+	unsigned long flags;
+	u16 type, t;
+
+	switch (flow_type & IRQ_TYPE_SENSE_MASK) {
+	case IRQ_TYPE_EDGE_FALLING:
+		type = REALTEK_GPIO_IRQ_EDGE_FALLING;
+		break;
+	case IRQ_TYPE_EDGE_RISING:
+		type = REALTEK_GPIO_IRQ_EDGE_RISING;
+		break;
+	case IRQ_TYPE_EDGE_BOTH:
+		type = REALTEK_GPIO_IRQ_EDGE_BOTH;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	irq_set_handler_locked(data, handle_edge_irq);
+
+	raw_spin_lock_irqsave(&ctrl->lock, flags);
+	t = ctrl->intr_type[port];
+	t &= ~realtek_gpio_imr_bits(port_pin, REALTEK_GPIO_IMR_LINE_MASK);
+	t |= realtek_gpio_imr_bits(port_pin, type);
+	ctrl->intr_type[port] = t;
+	realtek_gpio_write_imr(ctrl, port, t, ctrl->intr_mask[port]);
+	raw_spin_unlock_irqrestore(&ctrl->lock, flags);
+
+	return 0;
+}
+
+static void realtek_gpio_irq_handler(struct irq_desc *desc)
+{
+	struct gpio_chip *gc = irq_desc_get_handler_data(desc);
+	struct realtek_gpio_ctrl *ctrl = gpiochip_get_data(gc);
+	struct irq_chip *irq_chip = irq_desc_get_chip(desc);
+	unsigned int lines_done;
+	unsigned int port_pin_count;
+	unsigned int irq;
+	unsigned long status;
+	int offset;
+
+	chained_irq_enter(irq_chip, desc);
+
+	for (lines_done = 0; lines_done < gc->ngpio; lines_done += 8) {
+		status = realtek_gpio_read_isr(ctrl, lines_done / 8);
+		port_pin_count = min(gc->ngpio - lines_done, 8U);
+		for_each_set_bit(offset, &status, port_pin_count) {
+			irq = irq_find_mapping(gc->irq.domain, offset);
+			generic_handle_irq(irq);
+		}
+	}
+
+	chained_irq_exit(irq_chip, desc);
+}
+
+static int realtek_gpio_irq_init(struct gpio_chip *gc)
+{
+	struct realtek_gpio_ctrl *ctrl = gpiochip_get_data(gc);
+	unsigned int port;
+
+	for (port = 0; (port * 8) < gc->ngpio; port++) {
+		realtek_gpio_write_imr(ctrl, port, 0, 0);
+		realtek_gpio_clear_isr(ctrl, port, GENMASK(7, 0));
+	}
+
+	return 0;
+}
+
+static struct irq_chip realtek_gpio_irq_chip = {
+	.name = "realtek-otto-gpio",
+	.irq_ack = realtek_gpio_irq_ack,
+	.irq_mask = realtek_gpio_irq_mask,
+	.irq_unmask = realtek_gpio_irq_unmask,
+	.irq_set_type = realtek_gpio_irq_set_type,
+};
+
+static const struct of_device_id realtek_gpio_of_match[] = {
+	{
+		.compatible = "realtek,otto-gpio",
+		.data = (void *)GPIO_INTERRUPTS_DISABLED,
+	},
+	{
+		.compatible = "realtek,rtl8380-gpio",
+	},
+	{
+		.compatible = "realtek,rtl8390-gpio",
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, realtek_gpio_of_match);
+
+static int realtek_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	unsigned int dev_flags;
+	struct gpio_irq_chip *girq;
+	struct realtek_gpio_ctrl *ctrl;
+	u32 ngpios;
+	int err, irq;
+
+	ctrl = devm_kzalloc(dev, sizeof(*ctrl), GFP_KERNEL);
+	if (!ctrl)
+		return -ENOMEM;
+
+	dev_flags = (unsigned int) device_get_match_data(dev);
+
+	ngpios = REALTEK_GPIO_MAX;
+	device_property_read_u32(dev, "ngpios", &ngpios);
+
+	if (ngpios > REALTEK_GPIO_MAX) {
+		dev_err(&pdev->dev, "invalid ngpios (max. %d)\n",
+			REALTEK_GPIO_MAX);
+		return -EINVAL;
+	}
+
+	ctrl->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ctrl->base))
+		return PTR_ERR(ctrl->base);
+
+	raw_spin_lock_init(&ctrl->lock);
+
+	err = bgpio_init(&ctrl->gc, dev, 4,
+		ctrl->base + REALTEK_GPIO_REG_DATA, NULL, NULL,
+		ctrl->base + REALTEK_GPIO_REG_DIR, NULL,
+		BGPIOF_BIG_ENDIAN_BYTE_ORDER);
+	if (err) {
+		dev_err(dev, "unable to init generic GPIO");
+		return err;
+	}
+
+	ctrl->gc.ngpio = ngpios;
+	ctrl->gc.owner = THIS_MODULE;
+
+	irq = platform_get_irq_optional(pdev, 0);
+	if (!(dev_flags & GPIO_INTERRUPTS_DISABLED) && irq > 0) {
+		girq = &ctrl->gc.irq;
+		girq->chip = &realtek_gpio_irq_chip;
+		girq->default_type = IRQ_TYPE_NONE;
+		girq->handler = handle_bad_irq;
+		girq->parent_handler = realtek_gpio_irq_handler;
+		girq->num_parents = 1;
+		girq->parents = devm_kcalloc(dev, girq->num_parents,
+					sizeof(*girq->parents),	GFP_KERNEL);
+		if (!girq->parents)
+			return -ENOMEM;
+		girq->parents[0] = irq;
+		girq->init_hw = realtek_gpio_irq_init;
+	}
+
+	return devm_gpiochip_add_data(dev, &ctrl->gc, ctrl);
+}
+
+static struct platform_driver realtek_gpio_driver = {
+	.driver = {
+		.name = "realtek-otto-gpio",
+		.of_match_table	= realtek_gpio_of_match,
+	},
+	.probe = realtek_gpio_probe,
+};
+module_platform_driver(realtek_gpio_driver);
+
+MODULE_DESCRIPTION("Realtek Otto GPIO support");
+MODULE_AUTHOR("Sander Vanheule <[e-mail]>");
+MODULE_LICENSE("GPL v2");