i2c: add zhaoxin i2c controller driver

Add Zhaoxin I2C controller driver. It provides the access to the i2c
busses, which connects to the touchpad, eeprom, I2S, etc.

Zhaoxin I2C controller has two separate busses, so may accommodate up
to two I2C adapters. Those adapters are listed in the ACPI namespace
with the IIC1D17 HID, and probed by a platform driver.

The driver works with IRQ mode, and supports basic I2C features. Flags
I2C_AQ_NO_ZERO_LEN and I2C_AQ_COMB_WRITE_THEN_READ are used to limit
the unsupported access.

Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Hans Hu <hanshu-oc@zhaoxin.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

Author: Hans Hu

MAINTAINERS

@@ -10258,6 +10258,14 @@ L:	linux-i2c@vger.kernel.org
 F:	Documentation/i2c/busses/i2c-ismt.rst
 F:	drivers/i2c/busses/i2c-ismt.c
 
+I2C/SMBUS ZHAOXIN DRIVER
+M:	Hans Hu <hanshu@zhaoxin.com>
+L:	linux-i2c@vger.kernel.org
+S:	Maintained
+W:	https://www.zhaoxin.com
+F:	drivers/i2c/busses/i2c-viai2c-common.c
+F:	drivers/i2c/busses/i2c-viai2c-zhaoxin.c
+
 I2C/SMBUS STUB DRIVER
 M:	Jean Delvare <jdelvare@suse.com>
 L:	linux-i2c@vger.kernel.org

drivers/i2c/busses/Kconfig

@@ -344,6 +344,16 @@ config I2C_VIAPRO
 
 if ACPI
 
+config I2C_ZHAOXIN
+	tristate "Zhaoxin I2C Interface"
+	depends on PCI || COMPILE_TEST
+	help
+	  If you say yes to this option, support will be included for the
+	  ZHAOXIN I2C interface
+
+	  This driver can also be built as a module. If so, the module
+	  will be called i2c-zhaoxin.
+
 comment "ACPI drivers"
 
 config I2C_SCMI

drivers/i2c/busses/Makefile

@@ -29,6 +29,8 @@ obj-$(CONFIG_I2C_SIS630)	+= i2c-sis630.o
 obj-$(CONFIG_I2C_SIS96X)	+= i2c-sis96x.o
 obj-$(CONFIG_I2C_VIA)		+= i2c-via.o
 obj-$(CONFIG_I2C_VIAPRO)	+= i2c-viapro.o
+i2c-zhaoxin-objs := i2c-viai2c-zhaoxin.o i2c-viai2c-common.o
+obj-$(CONFIG_I2C_ZHAOXIN)	+= i2c-zhaoxin.o
 
 # Mac SMBus host controller drivers
 obj-$(CONFIG_I2C_HYDRA)		+= i2c-hydra.o

drivers/i2c/busses/i2c-viai2c-common.c

@@ -60,7 +60,7 @@ static int viai2c_write(struct viai2c *i2c, struct i2c_msg *pmsg, int last)
 	return i2c->ret;
 }
 
-static int viai2c_read(struct viai2c *i2c, struct i2c_msg *pmsg)
+static int viai2c_read(struct viai2c *i2c, struct i2c_msg *pmsg, bool first)
 {
 	u16 val, tcr_val = i2c->tcr;
 
@@ -81,7 +81,8 @@ static int viai2c_read(struct viai2c *i2c, struct i2c_msg *pmsg)
 
 	writew(tcr_val, i2c->base + VIAI2C_REG_TCR);
 
-	if (i2c->platform == VIAI2C_PLAT_WMT && (pmsg->flags & I2C_M_NOSTART)) {
+	if ((i2c->platform == VIAI2C_PLAT_WMT && (pmsg->flags & I2C_M_NOSTART)) ||
+	    (i2c->platform == VIAI2C_PLAT_ZHAOXIN && !first)) {
 		val = readw(i2c->base + VIAI2C_REG_CR);
 		val |= VIAI2C_CR_CPU_RDY;
 		writew(val, i2c->base + VIAI2C_REG_CR);
@@ -100,6 +101,7 @@ int viai2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 	int ret = 0;
 	struct viai2c *i2c = i2c_get_adapdata(adap);
 
+	i2c->mode = VIAI2C_BYTE_MODE;
 	for (i = 0; ret >= 0 && i < num; i++) {
 		pmsg = &msgs[i];
 		if (i2c->platform == VIAI2C_PLAT_WMT && !(pmsg->flags & I2C_M_NOSTART)) {
@@ -112,7 +114,7 @@ int viai2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 		i2c->xfered_len = 0;
 
 		if (pmsg->flags & I2C_M_RD)
-			ret = viai2c_read(i2c, pmsg);
+			ret = viai2c_read(i2c, pmsg, i == 0);
 		else
 			ret = viai2c_write(i2c, pmsg, (i + 1) == num);
 	}
@@ -157,6 +159,8 @@ static int viai2c_irq_xfer(struct viai2c *i2c)
 		if ((i2c->xfered_len + 1) == msg->len) {
 			if (i2c->platform == VIAI2C_PLAT_WMT && !i2c->last)
 				writew(VIAI2C_CR_ENABLE, base + VIAI2C_REG_CR);
+			else if (i2c->platform == VIAI2C_PLAT_ZHAOXIN && i2c->last)
+				writeb(VIAI2C_CR_TX_END, base + VIAI2C_REG_CR);
 		} else {
 			writew(msg->buf[i2c->xfered_len + 1] & 0xFF, base + VIAI2C_REG_CDR);
 			writew(VIAI2C_CR_CPU_RDY | VIAI2C_CR_ENABLE, base + VIAI2C_REG_CR);
@@ -168,13 +172,21 @@ static int viai2c_irq_xfer(struct viai2c *i2c)
 	return i2c->xfered_len == msg->len;
 }
 
+int __weak viai2c_fifo_irq_xfer(struct viai2c *i2c, bool irq)
+{
+	return 0;
+}
+
 static irqreturn_t viai2c_isr(int irq, void *data)
 {
 	struct viai2c *i2c = data;
 	u8 status;
 
 	/* save the status and write-clear it */
 	status = readw(i2c->base + VIAI2C_REG_ISR);
+	if (!status && i2c->platform == VIAI2C_PLAT_ZHAOXIN)
+		return IRQ_NONE;
+
 	writew(status, i2c->base + VIAI2C_REG_ISR);
 
 	i2c->ret = 0;
@@ -184,8 +196,12 @@ static irqreturn_t viai2c_isr(int irq, void *data)
 	if (i2c->platform == VIAI2C_PLAT_WMT && (status & VIAI2C_ISR_SCL_TIMEOUT))
 		i2c->ret = -ETIMEDOUT;
 
-	if (!i2c->ret)
-		i2c->ret = viai2c_irq_xfer(i2c);
+	if (!i2c->ret) {
+		if (i2c->mode == VIAI2C_BYTE_MODE)
+			i2c->ret = viai2c_irq_xfer(i2c);
+		else
+			i2c->ret = viai2c_fifo_irq_xfer(i2c, true);
+	}
 
 	/* All the data has been successfully transferred or error occurred */
 	if (i2c->ret)
@@ -214,6 +230,11 @@ int viai2c_init(struct platform_device *pdev, struct viai2c **pi2c, int plat)
 		i2c->irq = irq_of_parse_and_map(np, 0);
 		if (!i2c->irq)
 			return -EINVAL;
+	} else if (plat == VIAI2C_PLAT_ZHAOXIN) {
+		irq_flags = IRQF_SHARED;
+		i2c->irq = platform_get_irq(pdev, 0);
+		if (i2c->irq < 0)
+			return i2c->irq;
 	} else {
 		return dev_err_probe(&pdev->dev, -EINVAL, "wrong platform type\n");
 	}

drivers/i2c/busses/i2c-viai2c-common.h

@@ -52,6 +52,12 @@
 
 enum {
 	VIAI2C_PLAT_WMT,
+	VIAI2C_PLAT_ZHAOXIN
+};
+
+enum {
+	VIAI2C_BYTE_MODE,
+	VIAI2C_FIFO_MODE
 };
 
 struct viai2c {
@@ -66,11 +72,14 @@ struct viai2c {
 	struct i2c_msg		*msg;
 	int			ret;
 	bool			last;
+	unsigned int		mode;
 	unsigned int		platform;
+	void			*pltfm_priv;
 };
 
 int viai2c_wait_bus_not_busy(struct viai2c *i2c);
 int viai2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num);
 int viai2c_init(struct platform_device *pdev, struct viai2c **pi2c, int plat);
+int viai2c_fifo_irq_xfer(struct viai2c *i2c, bool irq);
 
 #endif