[v2,1/2] i2c: loongson: add bus driver for the loongson i2c controller

diff --git a/MAINTAINERS b/MAINTAINERS
index b8a02a60973d..95f26184e17c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12058,6 +12058,12 @@  S:	Maintained
 F:	Documentation/devicetree/bindings/gpio/loongson,ls-gpio.yaml
 F:	drivers/gpio/gpio-loongson-64bit.c
 
+LOONGSON I2C DRIVER
+M:	Yinbo Zhu <zhuyinbo@loongson.cn>
+L:	linux-i2c@vger.kernel.org
+S:	Maintained
+F:	drivers/i2c/busses/i2c-loongson.c
+
 LSILOGIC MPT FUSION DRIVERS (FC/SAS/SPI)
 M:	Sathya Prakash <sathya.prakash@broadcom.com>
 M:	Sreekanth Reddy <sreekanth.reddy@broadcom.com>
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index e50f9603d189..25b22b54504a 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -751,6 +751,16 @@  config I2C_KEMPLD
 	  This driver can also be built as a module. If so, the module
 	  will be called i2c-kempld.
 
+config I2C_LOONGSON
+        tristate "Loongson I2C controller"
+        depends on LOONGARCH || COMPILE_TEST
+        help
+          If you say yes to this option, support will be included for the
+          built-in I2C interface on the Loongson series Platform.
+
+          This driver can also be built as a module. If so, the module
+          will be called i2c-loongson.
+
 config I2C_LPC2K
 	tristate "I2C bus support for NXP LPC2K/LPC178x/18xx/43xx"
 	depends on OF && (ARCH_LPC18XX || COMPILE_TEST)
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index e73cdb1d2b5a..28a3fd18ffaf 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -76,6 +76,7 @@  obj-$(CONFIG_I2C_IMX_LPI2C)	+= i2c-imx-lpi2c.o
 obj-$(CONFIG_I2C_IOP3XX)	+= i2c-iop3xx.o
 obj-$(CONFIG_I2C_JZ4780)	+= i2c-jz4780.o
 obj-$(CONFIG_I2C_KEMPLD)	+= i2c-kempld.o
+obj-$(CONFIG_I2C_LOONGSON)	+= i2c-loongson.o
 obj-$(CONFIG_I2C_LPC2K)		+= i2c-lpc2k.o
 obj-$(CONFIG_I2C_MESON)		+= i2c-meson.o
 obj-$(CONFIG_I2C_MICROCHIP_CORE)	+= i2c-microchip-corei2c.o
diff --git a/drivers/i2c/busses/i2c-loongson.c b/drivers/i2c/busses/i2c-loongson.c
new file mode 100644
index 000000000000..14afb8cd627b
--- /dev/null
+++ b/drivers/i2c/busses/i2c-loongson.c
@@ -0,0 +1,547 @@ 
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Author: Yinbo Zhu <zhuyinbo@loongson.cn>
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define LOONGSON_I2C_ADDR_A7(x)		(x & 0x7f)
+
+#define LOONGSON_I2C_PRER_LO_REG	0x0
+#define LOONGSON_I2C_PRER_HI_REG	0x1
+#define LOONGSON_I2C_CTR_REG		0x2
+#define LOONGSON_I2C_TXR_REG		0x3
+#define LOONGSON_I2C_RXR_REG		0x3
+#define LOONGSON_I2C_CR_REG		0x4
+#define LOONGSON_I2C_SR_REG		0x4
+#define LOONGSON_I2C_BLTOP_REG		0x5
+#define LOONGSON_I2C_SADDR_REG		0x7
+
+#define CTR_EN				BIT(7)
+#define CTR_IEN				BIT(6)
+#define CTR_TXROK			BIT(4)
+#define CTR_RXROK			BIT(3)
+
+#define CR_START			BIT(7)
+#define CR_STOP				BIT(6)
+#define CR_READ				BIT(5)
+#define CR_WRITE			BIT(4)
+#define CR_ACK				BIT(3)
+#define CR_IACK				BIT(0)
+
+#define SR_NOACK			BIT(7)
+#define SR_BUSY				BIT(6)
+#define SR_AL				BIT(5)
+#define SR_SLAVE_ADDRESSED		BIT(4)
+#define SR_SLAVE_RW			BIT(3)
+#define SR_TIP				BIT(1)
+#define SR_IF				BIT(0)
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+enum loongson_i2c_slave_state {
+	LOONGSON_I2C_SLAVE_STOP,
+	LOONGSON_I2C_SLAVE_START,
+	LOONGSON_I2C_SLAVE_READ_REQUESTED,
+	LOONGSON_I2C_SLAVE_READ_PROCESSED,
+	LOONGSON_I2C_SLAVE_WRITE_REQUESTED,
+	LOONGSON_I2C_SLAVE_WRITE_RECEIVED,
+};
+#endif
+
+struct loongson_i2c_dev {
+	struct i2c_adapter	adapter;
+	unsigned int		suspended:1;
+	struct device		*dev;
+	void __iomem		*base;
+	int			irq;
+	u32			speed_hz;
+	struct completion	cmd_complete;
+	spinlock_t		lock;
+	struct resource		*ioarea;
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	struct i2c_client	*slave;
+	enum loongson_i2c_slave_state	slave_state;
+#endif
+};
+
+static inline u8 i2c_readb(struct loongson_i2c_dev *dev, u8 offset)
+{
+	return readb(dev->base + offset);
+}
+
+static inline void i2c_writeb(struct loongson_i2c_dev *dev, u8 val,
+			      u8 offset)
+{
+	writeb(val, dev->base + offset);
+}
+
+static int loongson_i2c_stop(struct loongson_i2c_dev *dev)
+{
+	unsigned long time_left;
+
+	do {
+		i2c_writeb(dev, CR_STOP | CR_IACK, LOONGSON_I2C_CR_REG);
+		time_left = wait_for_completion_timeout(&dev->cmd_complete,
+							dev->adapter.timeout);
+		if (!time_left)
+			return -ETIMEDOUT;
+
+	} while (i2c_readb(dev, LOONGSON_I2C_SR_REG) & SR_BUSY);
+
+	return 0;
+}
+
+static int loongson_i2c_start(struct loongson_i2c_dev *dev, int dev_addr,
+			      int flags)
+{
+	int ret;
+	unsigned long time_left;
+	int retry = 5;
+	unsigned char addr = LOONGSON_I2C_ADDR_A7(dev_addr) << 1;
+
+	addr |= (flags & I2C_M_RD) ? 1 : 0;
+
+	do {
+		mdelay(1);
+		i2c_writeb(dev, addr, LOONGSON_I2C_TXR_REG);
+		i2c_writeb(dev, (CR_START | CR_WRITE | CR_IACK),
+			   LOONGSON_I2C_CR_REG);
+		time_left = wait_for_completion_timeout(&dev->cmd_complete,
+							dev->adapter.timeout);
+		if (!time_left)
+			return -ETIMEDOUT;
+
+		if (i2c_readb(dev, LOONGSON_I2C_SR_REG) & SR_NOACK) {
+			ret = loongson_i2c_stop(dev);
+			if (ret)
+				return ret;
+		} else
+			break;
+	} while (retry--);
+
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+static void loongson_i2c_slave_init(struct loongson_i2c_dev *dev,
+				    u16 slave_addr)
+{
+	i2c_writeb(dev, LOONGSON_I2C_ADDR_A7(slave_addr),
+		   LOONGSON_I2C_SADDR_REG);
+	i2c_writeb(dev, 0xc0, LOONGSON_I2C_CTR_REG);
+}
+
+static int loongson_i2c_reg_slave(struct i2c_client *client)
+{
+	unsigned long flags;
+	struct loongson_i2c_dev *dev = i2c_get_adapdata(client->adapter);
+
+	if (dev->slave)
+		return -EINVAL;
+
+	loongson_i2c_slave_init(dev, client->addr);
+
+	dev->slave = client;
+	dev->slave_state = LOONGSON_I2C_SLAVE_STOP;
+
+	return 0;
+}
+
+static int loongson_i2c_unreg_slave(struct i2c_client *client)
+{
+	unsigned long flags;
+	struct loongson_i2c_dev *dev = i2c_get_adapdata(client->adapter);
+
+	if (!dev->slave)
+		return -EINVAL;
+
+	i2c_writeb(dev, 0xa0, LOONGSON_I2C_CTR_REG);
+
+	dev->slave = NULL;
+
+	return 0;
+}
+#endif
+
+static void loongson_i2c_reginit(struct loongson_i2c_dev *dev)
+{
+	u16 prer_val;
+	u32 pclk;
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	if (dev->slave) {
+		loongson_i2c_slave_init(dev, dev->slave->addr);
+		return;
+	}
+#endif
+	if (!dev->speed_hz) {
+		prer_val = 0x12c;
+	} else {
+		pclk = 50000000;
+		prer_val = pclk / (5 * dev->speed_hz) - 1;
+	}
+
+	i2c_writeb(dev, i2c_readb(dev, LOONGSON_I2C_CR_REG) |
+		   0x01, LOONGSON_I2C_CR_REG);
+	i2c_writeb(dev, i2c_readb(dev, LOONGSON_I2C_CTR_REG) & ~0x80,
+		   LOONGSON_I2C_CTR_REG);
+	i2c_writeb(dev, prer_val & GENMASK(7, 0), LOONGSON_I2C_PRER_LO_REG);
+	i2c_writeb(dev, (prer_val & GENMASK(15, 8)) >> 8,
+		   LOONGSON_I2C_PRER_HI_REG);
+	i2c_writeb(dev, i2c_readb(dev, LOONGSON_I2C_CTR_REG) |
+		   0xe0, LOONGSON_I2C_CTR_REG);
+}
+
+static int loongson_i2c_read(struct loongson_i2c_dev *dev, unsigned char *buf,
+			     int count)
+{
+	int i;
+	unsigned long time_left;
+
+	for (i = 0; i < count; i++) {
+		i2c_writeb(dev, (i == count - 1) ?
+			(CR_READ | CR_IACK | CR_ACK) : (CR_READ | CR_IACK),
+			LOONGSON_I2C_CR_REG);
+
+		time_left = wait_for_completion_timeout(&dev->cmd_complete,
+							dev->adapter.timeout);
+		if (!time_left)
+			return -ETIMEDOUT;
+
+		buf[i] = i2c_readb(dev, LOONGSON_I2C_RXR_REG);
+	}
+
+	return i;
+}
+
+static int loongson_i2c_write(struct loongson_i2c_dev *dev, unsigned char *buf,
+			      int count)
+{
+	int i;
+	int ret;
+	unsigned long time_left;
+
+	for (i = 0; i < count; i++) {
+		i2c_writeb(dev, buf[i], LOONGSON_I2C_TXR_REG);
+		i2c_writeb(dev, CR_WRITE | CR_IACK, LOONGSON_I2C_CR_REG);
+		time_left = wait_for_completion_timeout(&dev->cmd_complete,
+							dev->adapter.timeout);
+		if (!time_left)
+			return -ETIMEDOUT;
+
+		if (i2c_readb(dev, LOONGSON_I2C_SR_REG) & SR_NOACK) {
+			ret = loongson_i2c_stop(dev);
+			if (ret)
+				return ret;
+			return 0;
+		}
+	}
+
+	return i;
+}
+
+static int loongson_i2c_doxfer(struct loongson_i2c_dev *dev, struct i2c_msg *msgs,
+			       int num)
+{
+	int i, ret;
+	struct i2c_msg *m = msgs;
+
+	for (i = 0; i < num; i++) {
+		reinit_completion(&dev->cmd_complete);
+		ret = loongson_i2c_start(dev, m->addr, m->flags);
+		if (ret)
+			return ret;
+
+		if (m->flags & I2C_M_RD) {
+			ret = loongson_i2c_read(dev, m->buf, m->len);
+			if (ret)
+				return ret;
+		}
+
+		if (!(m->flags & I2C_M_RD)) {
+			ret = loongson_i2c_write(dev, m->buf, m->len);
+			if (ret)
+				return ret;
+		}
+
+		++m;
+	}
+
+	ret = loongson_i2c_stop(dev);
+	if (ret)
+		return ret;
+
+	return i;
+}
+
+static int loongson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			     int num)
+{
+	int ret;
+	int retry;
+	struct loongson_i2c_dev *dev;
+
+	dev = i2c_get_adapdata(adap);
+	for (retry = 0; retry < adap->retries; retry++) {
+		ret = loongson_i2c_doxfer(dev, msgs, num);
+		if (ret != -EAGAIN)
+			return ret;
+
+		udelay(100);
+	}
+
+	return -EREMOTEIO;
+}
+
+static unsigned int loongson_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm loongson_i2c_algo = {
+	.master_xfer	= loongson_i2c_xfer,
+	.functionality	= loongson_i2c_func,
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+	.reg_slave	= loongson_i2c_reg_slave,
+	.unreg_slave	= loongson_i2c_unreg_slave,
+#endif
+};
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+static bool loongson_i2c_slave_irq(struct loongson_i2c_dev *dev)
+{
+	u32 stat;
+	struct i2c_client *slave = dev->slave;
+	u8 value;
+
+	stat = i2c_readb(dev, LOONGSON_I2C_SR_REG);
+
+	if (stat & SR_SLAVE_ADDRESSED) {
+		dev->slave_state = LOONGSON_I2C_SLAVE_START;
+		i2c_writeb(dev, CTR_RXROK | CTR_EN | CTR_IEN,
+			LOONGSON_I2C_CTR_REG);
+	}
+
+	if (dev->slave_state == LOONGSON_I2C_SLAVE_STOP)
+		return IRQ_NONE;
+
+	if (dev->slave_state == LOONGSON_I2C_SLAVE_START)
+		if (stat & SR_SLAVE_RW)
+			dev->slave_state =
+				LOONGSON_I2C_SLAVE_READ_REQUESTED;
+		else
+			dev->slave_state =
+				LOONGSON_I2C_SLAVE_WRITE_REQUESTED;
+
+	if (stat & SR_NOACK)
+		dev->slave_state = LOONGSON_I2C_SLAVE_STOP;
+
+	value = i2c_readb(dev, LOONGSON_I2C_RXR_REG);
+	switch (dev->slave_state) {
+	case LOONGSON_I2C_SLAVE_READ_REQUESTED:
+		dev->slave_state = LOONGSON_I2C_SLAVE_READ_PROCESSED;
+		i2c_slave_event(
+			slave, LOONGSON_I2C_SLAVE_READ_REQUESTED, &value);
+		i2c_writeb(dev, value, LOONGSON_I2C_TXR_REG);
+		i2c_writeb(dev, CTR_TXROK | CTR_EN | CTR_IEN, LOONGSON_I2C_CTR_REG);
+		break;
+	case LOONGSON_I2C_SLAVE_READ_PROCESSED:
+		i2c_slave_event(
+			slave, LOONGSON_I2C_SLAVE_READ_PROCESSED, &value);
+		i2c_writeb(dev, value, LOONGSON_I2C_TXR_REG);
+		i2c_writeb(dev, CTR_TXROK | CTR_EN | CTR_IEN, LOONGSON_I2C_CTR_REG);
+		break;
+	case LOONGSON_I2C_SLAVE_WRITE_REQUESTED:
+		dev->slave_state = LOONGSON_I2C_SLAVE_WRITE_RECEIVED;
+		i2c_slave_event(
+			slave, LOONGSON_I2C_SLAVE_WRITE_REQUESTED, &value);
+		break;
+	case LOONGSON_I2C_SLAVE_WRITE_RECEIVED:
+		i2c_slave_event(
+			slave, LOONGSON_I2C_SLAVE_WRITE_RECEIVED, &value);
+		i2c_writeb(dev, CTR_RXROK | CTR_EN | CTR_IEN, LOONGSON_I2C_CTR_REG);
+		break;
+	case LOONGSON_I2C_SLAVE_STOP:
+		i2c_slave_event(slave, LOONGSON_I2C_SLAVE_STOP, &value);
+		i2c_writeb(dev, 0, LOONGSON_I2C_TXR_REG);
+		i2c_writeb(dev, CTR_TXROK | CTR_EN | CTR_IEN, LOONGSON_I2C_CTR_REG);
+		break;
+	default:
+		dev_err(dev->dev,
+			"unhandled slave_state: %d\n", dev->slave_state);
+		break;
+	}
+
+out:
+	return IRQ_HANDLED;
+}
+#endif
+
+static irqreturn_t loongson_i2c_isr(int this_irq, void *dev_id)
+{
+	unsigned char iflag;
+	struct loongson_i2c_dev *dev = dev_id;
+
+	iflag = i2c_readb(dev, LOONGSON_I2C_SR_REG);
+
+	if (iflag & SR_IF) {
+		i2c_writeb(dev, CR_IACK, LOONGSON_I2C_CR_REG);
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+		if (dev->slave)
+			loongson_i2c_slave_irq(dev);
+#endif
+		if (!(iflag & SR_TIP))
+			complete(&dev->cmd_complete);
+	} else
+		return IRQ_NONE;
+
+	return IRQ_HANDLED;
+}
+
+static int loongson_i2c_probe(struct platform_device *pdev)
+{
+	struct loongson_i2c_dev	*dev;
+	void __iomem		*reg_base;
+	struct i2c_adapter	*adap;
+	int			ret, irq;
+	u32			bus_speed;
+
+	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(reg_base))
+		return PTR_ERR(reg_base);
+
+	bus_speed = i2c_acpi_find_bus_speed(&pdev->dev);
+	if (!bus_speed)
+		device_property_read_u32(&pdev->dev, "clock-frequency",
+					&bus_speed);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq <= 0)
+		return dev_err_probe(&pdev->dev, irq, "no irq resource\n");
+
+	init_completion(&dev->cmd_complete);
+
+	dev->dev = &pdev->dev;
+	dev->irq = irq;
+	dev->speed_hz = bus_speed;
+	dev->base = reg_base;
+
+	platform_set_drvdata(pdev, dev);
+
+	loongson_i2c_reginit(dev);
+
+	ret = devm_request_irq(&pdev->dev, irq, loongson_i2c_isr, IRQF_SHARED,
+			       dev_name(&pdev->dev), dev);
+	if (ret)
+		return ret;
+
+	adap = &dev->adapter;
+	i2c_set_adapdata(adap, dev);
+	adap->nr = pdev->id;
+	strscpy(adap->name, pdev->name, sizeof(adap->name));
+	adap->owner = THIS_MODULE;
+	adap->class = I2C_CLASS_HWMON;
+	adap->retries = 5;
+	adap->algo = &loongson_i2c_algo;
+	adap->dev.parent = &pdev->dev;
+	adap->dev.of_node = pdev->dev.of_node;
+	ACPI_COMPANION_SET(&adap->dev, ACPI_COMPANION(&pdev->dev));
+	device_set_node(&adap->dev, dev_fwnode(&pdev->dev));
+	adap->timeout = msecs_to_jiffies(100);
+
+	ret = i2c_add_adapter(adap);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int loongson_i2c_remove(struct platform_device *pdev)
+{
+	struct loongson_i2c_dev	*dev = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&dev->adapter);
+
+	return 0;
+}
+
+static int loongson_i2c_suspend_noirq(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct loongson_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
+
+	i2c_dev->suspended = 1;
+
+	return 0;
+}
+
+static int loongson_i2c_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct loongson_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
+
+	i2c_dev->suspended = 0;
+	loongson_i2c_reginit(i2c_dev);
+
+	return 0;
+}
+
+static const struct dev_pm_ops loongson_i2c_pm_ops = {
+	.suspend_noirq	= loongson_i2c_suspend_noirq,
+	.resume		= loongson_i2c_resume,
+};
+
+static const struct of_device_id loongson_i2c_id_table[] = {
+	{.compatible = "loongson,ls2k-i2c"},
+	{.compatible = "loongson,ls7a-i2c"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, loongson_i2c_id_table);
+
+static const struct acpi_device_id loongson_i2c_acpi_match[] = {
+	{"LOON0004"},
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, loongson_i2c_acpi_match);
+
+static struct platform_driver loongson_i2c_driver = {
+	.driver	= {
+		.name	= "loongson-i2c",
+		.owner	= THIS_MODULE,
+		.pm	= &loongson_i2c_pm_ops,
+		.of_match_table = loongson_i2c_id_table,
+		.acpi_match_table = loongson_i2c_acpi_match,
+	},
+	.probe		= loongson_i2c_probe,
+	.remove		= loongson_i2c_remove,
+};
+
+static int __init loongson_i2c_init_driver(void)
+{
+	return platform_driver_register(&loongson_i2c_driver);
+}
+subsys_initcall(loongson_i2c_init_driver);
+
+static void __exit loongson_i2c_exit_driver(void)
+{
+	platform_driver_unregister(&loongson_i2c_driver);
+}
+module_exit(loongson_i2c_exit_driver);
+
+MODULE_DESCRIPTION("Loongson i2c driver");
+MODULE_LICENSE("GPL");