i2c: ls2x: Add driver for Loongson-2K/LS7A I2C controller

This I2C module is integrated into the Loongson-2K SoCs and Loongson
LS7A bridge chip.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/Kconfig

@@ -761,6 +761,17 @@ config I2C_LPC2K
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-lpc2k.
 
+config I2C_LS2X
+	tristate "Loongson LS2X I2C adapter"
+	depends on MACH_LOONGSON64 || COMPILE_TEST
+	help
+	  If you say yes to this option, support will be included for the
+	  I2C interface on the Loongson-2K SoCs and Loongson LS7A bridge
+	  chip.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called i2c-ls2x.
+
 config I2C_MLXBF
         tristate "Mellanox BlueField I2C controller"
         depends on MELLANOX_PLATFORM && ARM64

drivers/i2c/busses/Makefile

@@ -77,6 +77,7 @@ obj-$(CONFIG_I2C_IOP3XX)	+= i2c-iop3xx.o
 obj-$(CONFIG_I2C_JZ4780)	+= i2c-jz4780.o
 obj-$(CONFIG_I2C_KEMPLD)	+= i2c-kempld.o
 obj-$(CONFIG_I2C_LPC2K)		+= i2c-lpc2k.o
+obj-$(CONFIG_I2C_LS2X)		+= i2c-ls2x.o
 obj-$(CONFIG_I2C_MESON)		+= i2c-meson.o
 obj-$(CONFIG_I2C_MICROCHIP_CORE)	+= i2c-microchip-corei2c.o
 obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o

drivers/i2c/busses/i2c-ls2x.c

@@ -0,0 +1,370 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Loongson-2K/Loongson LS7A I2C master mode driver
+ *
+ * Copyright (C) 2013 Loongson Technology Corporation Limited.
+ * Copyright (C) 2014-2017 Lemote, Inc.
+ * Copyright (C) 2018-2022 Loongson Technology Corporation Limited.
+ *
+ * Originally written by liushaozong
+ * Rewritten for mainline by Binbin Zhou <zhoubinbin@loongson.cn>
+ */
+
+#include <linux/bits.h>
+#include <linux/completion.h>
+#include <linux/device.h>
+#include <linux/iopoll.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pm_runtime.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/units.h>
+
+/* I2C Registers */
+#define I2C_LS2X_PRER		0x0 /* Freq Division Register(16 bits) */
+#define I2C_LS2X_CTR		0x2 /* Control Register */
+#define I2C_LS2X_TXR		0x3 /* Transport Data Register */
+#define I2C_LS2X_RXR		0x3 /* Receive Data Register */
+#define I2C_LS2X_CR		0x4 /* Command Control Register */
+#define I2C_LS2X_SR		0x4 /* State Register */
+
+/* Command Control Register Bit */
+#define LS2X_CR_START		BIT(7) /* Start signal */
+#define LS2X_CR_STOP		BIT(6) /* Stop signal */
+#define LS2X_CR_READ		BIT(5) /* Read signal */
+#define LS2X_CR_WRITE		BIT(4) /* Write signal */
+#define LS2X_CR_ACK		BIT(3) /* Response signal */
+#define LS2X_CR_IACK		BIT(0) /* Interrupt response signal */
+
+/* State Register Bit */
+#define LS2X_SR_NOACK		BIT(7) /* Receive NACK */
+#define LS2X_SR_BUSY		BIT(6) /* Bus busy state */
+#define LS2X_SR_AL		BIT(5) /* Arbitration lost */
+#define LS2X_SR_TIP		BIT(1) /* Transmission state */
+#define LS2X_SR_IF		BIT(0) /* Interrupt flag */
+
+/* Control Register Bit */
+#define LS2X_CTR_EN		BIT(7) /* 0: I2c frequency setting 1: Normal */
+#define LS2X_CTR_IEN		BIT(6) /* Enable i2c interrupt */
+#define LS2X_CTR_MST		BIT(5) /* 0: Slave mode 1: Master mode */
+#define CTR_FREQ_MASK		GENMASK(7, 6)
+#define CTR_READY_MASK		GENMASK(7, 5)
+
+/* The PCLK frequency from LPB */
+#define LS2X_I2C_PCLK_FREQ	(50 * HZ_PER_MHZ)
+
+/* The default bus frequency, which is an empirical value */
+#define LS2X_I2C_FREQ_STD	(33 * HZ_PER_KHZ)
+
+struct ls2x_i2c_priv {
+	struct i2c_adapter	adapter;
+	void __iomem		*base;
+	struct i2c_timings	i2c_t;
+	struct completion	cmd_complete;
+};
+
+/*
+ * Interrupt service routine.
+ * This gets called whenever an I2C interrupt occurs.
+ */
+static irqreturn_t ls2x_i2c_isr(int this_irq, void *dev_id)
+{
+	struct ls2x_i2c_priv *priv = dev_id;
+
+	if (!(readb(priv->base + I2C_LS2X_SR) & LS2X_SR_IF))
+		return IRQ_NONE;
+
+	writeb(LS2X_CR_IACK, priv->base + I2C_LS2X_CR);
+	complete(&priv->cmd_complete);
+	return IRQ_HANDLED;
+}
+
+/*
+ * The ls2x i2c controller supports standard mode and fast mode, so the
+ * maximum bus frequency is '400kHz'.
+ * The bus frequency is set to the empirical value of '33KHz' by default,
+ * but it can also be taken from ACPI or FDT for compatibility with more
+ * devices.
+ */
+static void ls2x_i2c_adjust_bus_speed(struct ls2x_i2c_priv *priv)
+{
+	struct i2c_timings *t = &priv->i2c_t;
+	struct device *dev = priv->adapter.dev.parent;
+	u32 acpi_speed = i2c_acpi_find_bus_speed(dev);
+
+	i2c_parse_fw_timings(dev, t, false);
+
+	if (acpi_speed || t->bus_freq_hz)
+		t->bus_freq_hz = max(t->bus_freq_hz, acpi_speed);
+	else
+		t->bus_freq_hz = LS2X_I2C_FREQ_STD;
+
+	/* Calculate and set i2c frequency. */
+	writew(LS2X_I2C_PCLK_FREQ / (5 * t->bus_freq_hz) - 1,
+	       priv->base + I2C_LS2X_PRER);
+}
+
+static void ls2x_i2c_init(struct ls2x_i2c_priv *priv)
+{
+	/* Set i2c frequency setting mode and disable interrupts. */
+	writeb(readb(priv->base + I2C_LS2X_CTR) & ~CTR_FREQ_MASK,
+	       priv->base + I2C_LS2X_CTR);
+
+	ls2x_i2c_adjust_bus_speed(priv);
+
+	/* Set i2c normal operating mode and enable interrupts. */
+	writeb(readb(priv->base + I2C_LS2X_CTR) | CTR_READY_MASK,
+	       priv->base + I2C_LS2X_CTR);
+}
+
+static int ls2x_i2c_xfer_byte(struct ls2x_i2c_priv *priv, u8 txdata, u8 *rxdatap)
+{
+	u8 rxdata;
+	unsigned long time_left;
+
+	writeb(txdata, priv->base + I2C_LS2X_CR);
+
+	time_left = wait_for_completion_timeout(&priv->cmd_complete,
+						priv->adapter.timeout);
+	if (!time_left)
+		return -ETIMEDOUT;
+
+	rxdata = readb(priv->base + I2C_LS2X_SR);
+	if (rxdatap)
+		*rxdatap = rxdata;
+
+	return 0;
+}
+
+static int ls2x_i2c_send_byte(struct ls2x_i2c_priv *priv, u8 txdata)
+{
+	int ret;
+	u8 rxdata;
+
+	ret = ls2x_i2c_xfer_byte(priv, txdata, &rxdata);
+	if (ret)
+		return ret;
+
+	if (rxdata & LS2X_SR_AL)
+		return -EAGAIN;
+
+	if (rxdata & LS2X_SR_NOACK)
+		return -ENXIO;
+
+	return 0;
+}
+
+static int ls2x_i2c_stop(struct ls2x_i2c_priv *priv)
+{
+	u8 value;
+
+	writeb(LS2X_CR_STOP, priv->base + I2C_LS2X_CR);
+	return readb_poll_timeout(priv->base + I2C_LS2X_SR, value,
+				  !(value & LS2X_SR_BUSY), 100,
+				  jiffies_to_usecs(priv->adapter.timeout));
+}
+
+static int ls2x_i2c_start(struct ls2x_i2c_priv *priv, struct i2c_msg *msgs)
+{
+	reinit_completion(&priv->cmd_complete);
+
+	writeb(i2c_8bit_addr_from_msg(msgs), priv->base + I2C_LS2X_TXR);
+	return ls2x_i2c_send_byte(priv, LS2X_CR_START | LS2X_CR_WRITE);
+}
+
+static int ls2x_i2c_rx(struct ls2x_i2c_priv *priv, struct i2c_msg *msg)
+{
+	int ret;
+	u8 rxdata, *buf = msg->buf;
+	u16 len = msg->len;
+
+	/* Contains steps to send start condition and address. */
+	ret = ls2x_i2c_start(priv, msg);
+	if (ret)
+		return ret;
+
+	while (len--) {
+		ret = ls2x_i2c_xfer_byte(priv,
+					 LS2X_CR_READ | (len ? 0 : LS2X_CR_ACK),
+					 &rxdata);
+		if (ret)
+			return ret;
+
+		*buf++ = readb(priv->base + I2C_LS2X_RXR);
+	}
+
+	return 0;
+}
+
+static int ls2x_i2c_tx(struct ls2x_i2c_priv *priv, struct i2c_msg *msg)
+{
+	int ret;
+	u8 *buf = msg->buf;
+	u16 len = msg->len;
+
+	/* Contains steps to send start condition and address. */
+	ret = ls2x_i2c_start(priv, msg);
+	if (ret)
+		return ret;
+
+	while (len--) {
+		writeb(*buf++, priv->base + I2C_LS2X_TXR);
+
+		ret = ls2x_i2c_send_byte(priv, LS2X_CR_WRITE);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int ls2x_i2c_xfer_one(struct ls2x_i2c_priv *priv,
+			     struct i2c_msg *msg, bool stop)
+{
+	int ret;
+
+	if (msg->flags & I2C_M_RD)
+		ret = ls2x_i2c_rx(priv, msg);
+	else
+		ret = ls2x_i2c_tx(priv, msg);
+
+	if (ret < 0) {
+		/* Fatel error. Needs reinit. */
+		if (ret == -ETIMEDOUT)
+			ls2x_i2c_init(priv);
+
+		return ret;
+	}
+
+	if (stop) {
+		/* Failed to issue STOP. Needs reinit. */
+		ret = ls2x_i2c_stop(priv);
+		if (ret)
+			ls2x_i2c_init(priv);
+	}
+
+	return ret;
+}
+
+static int ls2x_i2c_master_xfer(struct i2c_adapter *adap,
+				struct i2c_msg *msgs, int num)
+{
+	int ret;
+	struct i2c_msg *msg, *emsg = msgs + num;
+	struct ls2x_i2c_priv *priv = i2c_get_adapdata(adap);
+
+	for (msg = msgs; msg < emsg; msg++) {
+		ret = ls2x_i2c_xfer_one(priv, msg, msg == emsg - 1);
+		if (ret)
+			return ret;
+	}
+
+	return num;
+}
+
+static unsigned int ls2x_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm ls2x_i2c_algo = {
+	.master_xfer	= ls2x_i2c_master_xfer,
+	.functionality	= ls2x_i2c_func,
+};
+
+static int ls2x_i2c_probe(struct platform_device *pdev)
+{
+	int ret, irq;
+	struct i2c_adapter *adap;
+	struct ls2x_i2c_priv *priv;
+	struct device *dev = &pdev->dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	/* Map hardware registers */
+	priv->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	/* Add the i2c adapter */
+	adap = &priv->adapter;
+	adap->retries = 5;
+	adap->nr = pdev->id;
+	adap->dev.parent = dev;
+	adap->owner = THIS_MODULE;
+	adap->algo = &ls2x_i2c_algo;
+	adap->timeout = msecs_to_jiffies(100);
+	device_set_node(&adap->dev, dev_fwnode(dev));
+	i2c_set_adapdata(adap, priv);
+	strscpy(adap->name, pdev->name, sizeof(adap->name));
+	init_completion(&priv->cmd_complete);
+	platform_set_drvdata(pdev, priv);
+
+	ls2x_i2c_init(priv);
+
+	ret = devm_request_irq(dev, irq, ls2x_i2c_isr, IRQF_SHARED, "ls2x-i2c",
+			       priv);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Unable to request irq %d\n", irq);
+
+	return devm_i2c_add_adapter(dev, adap);
+}
+
+static int ls2x_i2c_suspend(struct device *dev)
+{
+	struct ls2x_i2c_priv *priv = dev_get_drvdata(dev);
+
+	/* Disable interrupts */
+	writeb(readb(priv->base + I2C_LS2X_CTR) & ~LS2X_CTR_IEN,
+	       priv->base + I2C_LS2X_CTR);
+
+	return 0;
+}
+
+static int ls2x_i2c_resume(struct device *dev)
+{
+	ls2x_i2c_init(dev_get_drvdata(dev));
+	return 0;
+}
+
+static DEFINE_RUNTIME_DEV_PM_OPS(ls2x_i2c_pm_ops,
+				 ls2x_i2c_suspend, ls2x_i2c_resume, NULL);
+
+static const struct of_device_id ls2x_i2c_id_table[] = {
+	{ .compatible = "loongson,ls2k-i2c" },
+	{ .compatible = "loongson,ls7a-i2c" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ls2x_i2c_id_table);
+
+static const struct acpi_device_id ls2x_i2c_acpi_match[] = {
+	{ "LOON0004" }, /* Loongson LS7A */
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, ls2x_i2c_acpi_match);
+
+static struct platform_driver ls2x_i2c_driver = {
+	.probe		= ls2x_i2c_probe,
+	.driver		= {
+		.name	= "ls2x-i2c",
+		.pm	= pm_sleep_ptr(&ls2x_i2c_pm_ops),
+		.of_match_table = ls2x_i2c_id_table,
+		.acpi_match_table = ls2x_i2c_acpi_match,
+	},
+};
+module_platform_driver(ls2x_i2c_driver);
+
+MODULE_DESCRIPTION("Loongson LS2X I2C Bus driver");
+MODULE_AUTHOR("Loongson Technology Corporation Limited");
+MODULE_LICENSE("GPL");