Message-Id: <20240503-congatec-board-controller-v2-3-681511a01c8f@bootlin.com>
Date: Tue, 17 Sep 2024 19:00:49 +0200
From: Thomas Richard <thomas.richard@...tlin.com>
To: Lee Jones <lee@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>, Andi Shyti <andi.shyti@...nel.org>, 
 Wim Van Sebroeck <wim@...ux-watchdog.org>, 
 Guenter Roeck <linux@...ck-us.net>
Cc: linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org, 
 linux-i2c@...r.kernel.org, linux-watchdog@...r.kernel.org, 
 thomas.petazzoni@...tlin.com, blake.vermeer@...sight.com, 
 Thomas Richard <thomas.richard@...tlin.com>
Subject: [PATCH v2 3/5] i2c: Congatec Board Controller i2c bus driver

Add i2c support for the Congatec Board Controller.

The Board Controller has two i2c busses, a General Purpose bus and a Power
Management bus.

Signed-off-by: Thomas Richard <thomas.richard@...tlin.com>
---
 drivers/i2c/busses/Kconfig    |  10 ++
 drivers/i2c/busses/Makefile   |   1 +
 drivers/i2c/busses/i2c-cgbc.c | 406 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 417 insertions(+)

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index a22f9125322a..ab58a4c79174 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -535,6 +535,16 @@ config I2C_CBUS_GPIO
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-cbus-gpio.
 
+config I2C_CGBC
+	tristate "Congatec I2C Controller"
+	depends on MFD_CGBC
+	help
+	  This driver supports the 2 I2C interfaces on the Congatec Board
+	  Controller.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called i2c-cgbc.ko.
+
 config I2C_CPM
 	tristate "Freescale CPM1 or CPM2 (MPC8xx/826x)"
 	depends on CPM1 || CPM2
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 78d0561339e5..3e6bb569c546 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_I2C_BCM2835)	+= i2c-bcm2835.o
 obj-$(CONFIG_I2C_BCM_IPROC)	+= i2c-bcm-iproc.o
 obj-$(CONFIG_I2C_CADENCE)	+= i2c-cadence.o
 obj-$(CONFIG_I2C_CBUS_GPIO)	+= i2c-cbus-gpio.o
+obj-$(CONFIG_I2C_CGBC)		+= i2c-cgbc.o
 obj-$(CONFIG_I2C_CPM)		+= i2c-cpm.o
 obj-$(CONFIG_I2C_DAVINCI)	+= i2c-davinci.o
 obj-$(CONFIG_I2C_DESIGNWARE_CORE)			+= i2c-designware-core.o
diff --git a/drivers/i2c/busses/i2c-cgbc.c b/drivers/i2c/busses/i2c-cgbc.c
new file mode 100644
index 000000000000..eba0b205de11
--- /dev/null
+++ b/drivers/i2c/busses/i2c-cgbc.c
@@ -0,0 +1,406 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Congatec Board Controller I2C busses driver
+ *
+ * Copyright (C) 2024 Bootlin
+ * Author: Thomas Richard <thomas.richard@...tlin.com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/iopoll.h>
+#include <linux/mfd/cgbc.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#define CGBC_I2C_PRIMARY_BUS_ID	0
+#define CGBC_I2C_PM_BUS_ID	4
+
+#define CGBC_I2C_CMD_START	0x40
+#define CGBC_I2C_CMD_STAT	0x48
+#define CGBC_I2C_CMD_DATA	0x50
+#define CGBC_I2C_CMD_SPEED	0x58
+
+#define CGBC_I2C_STAT_IDL	0x00
+#define CGBC_I2C_STAT_DAT	0x01
+#define CGBC_I2C_STAT_BUSY	0x02
+
+#define CGBC_I2C_START	0x80
+#define CGBC_I2C_STOP	0x40
+
+#define CGBC_I2C_LAST_ACK  0x80    /* send ACK on last read byte */
+
+/*
+ * Reference code defines 1kHz as min freq and 6.1MHz as max freq.
+ * But in practice, the board controller limits the frequency to 1MHz, and the
+ * 1kHz is not functional (minimal working freq is 50kHz).
+ * So use these values as limits.
+ */
+#define CGBC_I2C_FREQ_MIN_HZ	50000	/* 50 kHz */
+#define CGBC_I2C_FREQ_MAX_HZ	1000000 /* 1 MHz */
+
+#define CGBC_I2C_FREQ_UNIT_1KHZ		0x40
+#define CGBC_I2C_FREQ_UNIT_10KHZ	0x80
+#define CGBC_I2C_FREQ_UNIT_100KHZ	0xC0
+
+#define CGBC_I2C_FREQ_UNIT_MASK		0xC0
+#define CGBC_I2C_FREQ_VALUE_MASK	0x3F
+
+#define CGBC_I2C_READ_MAX_LEN	31
+#define CGBC_I2C_WRITE_MAX_LEN	32
+
+#define CGBC_I2C_CMD_HEADER_SIZE	4
+#define CGBC_I2C_CMD_SIZE		(CGBC_I2C_CMD_HEADER_SIZE + CGBC_I2C_WRITE_MAX_LEN)
+
+enum cgbc_i2c_state {
+	CGBC_I2C_STATE_DONE = 0,
+	CGBC_I2C_STATE_INIT,
+	CGBC_I2C_STATE_START,
+	CGBC_I2C_STATE_READ,
+	CGBC_I2C_STATE_WRITE,
+	CGBC_I2C_STATE_ERROR,
+};
+
+struct i2c_algo_cgbc_data {
+	u8		bus_id;
+	unsigned long	read_maxtime_us;
+};
+
+struct cgbc_i2c_data {
+	struct device		*dev;
+	struct cgbc_device_data *cgbc;
+	struct i2c_adapter      adap;
+	struct i2c_msg		*msg;
+	int			nmsgs;
+	int			pos;
+	enum cgbc_i2c_state	state;
+};
+
+struct cgbc_i2c_transfer {
+	u8 bus_id;
+	bool start;
+	bool stop;
+	bool last_ack;
+	u8 read;
+	u8 write;
+	u8 addr;
+	u8 data[CGBC_I2C_WRITE_MAX_LEN];
+};
+
+static u8 cgbc_i2c_freq_to_reg(unsigned int bus_frequency)
+{
+	u8 reg;
+
+	if (bus_frequency <= 10000)
+		reg = CGBC_I2C_FREQ_UNIT_1KHZ | (bus_frequency / 1000);
+	else if (bus_frequency <= 100000)
+		reg = CGBC_I2C_FREQ_UNIT_10KHZ | (bus_frequency / 10000);
+	else
+		reg = CGBC_I2C_FREQ_UNIT_100KHZ | (bus_frequency / 100000);
+
+	return reg;
+}
+
+static unsigned int cgbc_i2c_reg_to_freq(u8 reg)
+{
+	unsigned int freq = reg & CGBC_I2C_FREQ_VALUE_MASK;
+	u8 unit = reg & CGBC_I2C_FREQ_UNIT_MASK;
+
+	if (unit == CGBC_I2C_FREQ_UNIT_100KHZ)
+		return freq * 100000;
+	else if (unit == CGBC_I2C_FREQ_UNIT_10KHZ)
+		return freq * 10000;
+	else
+		return freq * 1000;
+}
+
+static int cgbc_i2c_get_status(struct i2c_adapter *adap)
+{
+	struct i2c_algo_cgbc_data *algo_data = adap->algo_data;
+	struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
+	struct cgbc_device_data *cgbc = i2c->cgbc;
+	u8 cmd = CGBC_I2C_CMD_STAT | algo_data->bus_id;
+	u8 status;
+	int ret;
+
+	ret = cgbc_command(cgbc, &cmd, sizeof(cmd), NULL, 0, &status);
+	if (ret)
+		return ret;
+
+	return status;
+}
+
+static int cgbc_i2c_set_frequency(struct i2c_adapter *adap,
+				  unsigned int bus_frequency)
+{
+	struct i2c_algo_cgbc_data *algo_data = adap->algo_data;
+	struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
+	struct cgbc_device_data *cgbc = i2c->cgbc;
+	u8 cmd[2], data;
+	int ret;
+
+	if (bus_frequency > CGBC_I2C_FREQ_MAX_HZ ||
+	    bus_frequency < CGBC_I2C_FREQ_MIN_HZ) {
+		dev_info(i2c->dev, "invalid frequency %u, using default\n", bus_frequency);
+		bus_frequency = I2C_MAX_STANDARD_MODE_FREQ;
+	}
+
+	cmd[0] = CGBC_I2C_CMD_SPEED | algo_data->bus_id;
+	cmd[1] = cgbc_i2c_freq_to_reg(bus_frequency);
+
+	ret = cgbc_command(cgbc, &cmd, sizeof(cmd), &data, 1, NULL);
+	if (ret)
+		return dev_err_probe(i2c->dev, ret,
+				     "Failed to initialize I2C bus %s",
+				     adap->name);
+
+	cmd[1] = 0x00;
+
+	ret = cgbc_command(cgbc, &cmd, sizeof(cmd), &data, 1, NULL);
+	if (ret)
+		return dev_err_probe(i2c->dev, ret,
+				     "Failed to get I2C bus frequency");
+
+	bus_frequency = cgbc_i2c_reg_to_freq(data);
+
+	dev_dbg(i2c->dev, "%s is running at %d Hz\n", adap->name, bus_frequency);
+
+	/*
+	 * The read_maxtime_us variable represents the maximum time to wait
+	 * for data during a read operation. The maximum amount of data that
+	 * can be read by a command is CGBC_I2C_READ_MAX_LEN.
+	 * Therefore, calculate the max time to properly size the timeout.
+	 */
+	algo_data->read_maxtime_us = (BITS_PER_BYTE + 1) * CGBC_I2C_READ_MAX_LEN
+		* USEC_PER_SEC / bus_frequency;
+
+	return 0;
+}
+
+static unsigned int cgbc_i2c_xfer_to_cmd(struct cgbc_i2c_transfer xfer, u8 *cmd)
+{
+	int i = 0;
+
+	cmd[i++] = CGBC_I2C_CMD_START | xfer.bus_id;
+
+	cmd[i] = (xfer.start) ? CGBC_I2C_START : 0x00;
+	if (xfer.stop)
+		cmd[i] |= CGBC_I2C_STOP;
+	cmd[i++] |= (xfer.start) ? xfer.write + 1 : xfer.write;
+
+	cmd[i++] = (xfer.last_ack) ? (xfer.read | CGBC_I2C_LAST_ACK) : xfer.read;
+
+	if (xfer.start)
+		cmd[i++] = xfer.addr;
+
+	if (xfer.write > 0)
+		memcpy(&cmd[i], &xfer.data, xfer.write);
+
+	return i + xfer.write;
+}
+
+static int cgbc_i2c_xfer_msg(struct i2c_adapter *adap)
+{
+	struct i2c_algo_cgbc_data *algo_data = adap->algo_data;
+	struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
+	struct cgbc_device_data *cgbc = i2c->cgbc;
+	struct i2c_msg *msg = i2c->msg;
+	u8 cmd[CGBC_I2C_CMD_SIZE];
+	int ret, max_len, len, i;
+	unsigned int cmd_len;
+	u8 cmd_data;
+
+	struct cgbc_i2c_transfer xfer = {
+		.bus_id = algo_data->bus_id,
+		.addr = i2c_8bit_addr_from_msg(msg),
+	};
+
+	if (i2c->state == CGBC_I2C_STATE_DONE)
+		return 0;
+
+	ret = cgbc_i2c_get_status(adap);
+
+	if (ret == CGBC_I2C_STAT_BUSY)
+		return -EBUSY;
+	else if (ret < 0)
+		goto err;
+
+	if (i2c->state == CGBC_I2C_STATE_INIT ||
+	    (i2c->state == CGBC_I2C_STATE_WRITE && msg->flags & I2C_M_RD))
+		xfer.start = true;
+
+	i2c->state = (msg->flags & I2C_M_RD) ? CGBC_I2C_STATE_READ : CGBC_I2C_STATE_WRITE;
+
+	max_len = (i2c->state == CGBC_I2C_STATE_READ) ?
+		CGBC_I2C_READ_MAX_LEN : CGBC_I2C_WRITE_MAX_LEN;
+
+	if (msg->len - i2c->pos > max_len) {
+		len = max_len;
+	} else {
+		len = msg->len - i2c->pos;
+
+		if (i2c->nmsgs == 1)
+			xfer.stop = true;
+	}
+
+	if (i2c->state == CGBC_I2C_STATE_WRITE) {
+		xfer.write = len;
+		xfer.read = 0;
+
+		for (i = 0; i < len; i++)
+			xfer.data[i] = msg->buf[i2c->pos + i];
+
+		cmd_len = cgbc_i2c_xfer_to_cmd(xfer, &cmd[0]);
+
+		ret = cgbc_command(cgbc, &cmd, cmd_len, NULL, 0, NULL);
+		if (ret)
+			goto err;
+	} else if (i2c->state == CGBC_I2C_STATE_READ) {
+		xfer.write = 0;
+		xfer.read = len;
+
+		if (i2c->nmsgs > 1 || msg->len - i2c->pos > max_len)
+			xfer.read |= CGBC_I2C_LAST_ACK;
+
+		cmd_len = cgbc_i2c_xfer_to_cmd(xfer, &cmd[0]);
+		ret = cgbc_command(cgbc, &cmd, cmd_len, NULL, 0, NULL);
+		if (ret)
+			goto err;
+
+		ret = read_poll_timeout(cgbc_i2c_get_status, ret,
+					ret != CGBC_I2C_STAT_BUSY, 0,
+					2 * algo_data->read_maxtime_us, false, adap);
+		if (ret < 0)
+			goto err;
+
+		cmd_data = CGBC_I2C_CMD_DATA | algo_data->bus_id;
+		ret = cgbc_command(cgbc, &cmd_data, sizeof(cmd_data),
+				   msg->buf + i2c->pos, len, NULL);
+		if (ret)
+			goto err;
+	}
+
+	if (len == (msg->len - i2c->pos)) {
+		i2c->msg++;
+		i2c->nmsgs--;
+		i2c->pos = 0;
+	} else {
+		i2c->pos += len;
+	}
+
+	if (i2c->nmsgs == 0)
+		i2c->state = CGBC_I2C_STATE_DONE;
+
+	return 0;
+
+err:
+	i2c->state = CGBC_I2C_STATE_ERROR;
+	return ret;
+}
+
+static int cgbc_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			 int num)
+{
+	struct cgbc_i2c_data *i2c = i2c_get_adapdata(adap);
+	unsigned long timeout = jiffies + HZ;
+	int ret;
+
+	i2c->state = CGBC_I2C_STATE_INIT;
+	i2c->msg = msgs;
+	i2c->nmsgs = num;
+	i2c->pos = 0;
+
+	while (time_before(jiffies, timeout)) {
+		ret = cgbc_i2c_xfer_msg(adap);
+		if (i2c->state == CGBC_I2C_STATE_DONE)
+			return num;
+
+		if (i2c->state == CGBC_I2C_STATE_ERROR)
+			return ret;
+
+		if (ret == 0)
+			timeout = jiffies + HZ;
+	}
+
+	i2c->state = CGBC_I2C_STATE_ERROR;
+	return -ETIMEDOUT;
+}
+
+static u32 cgbc_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~(I2C_FUNC_SMBUS_QUICK));
+}
+
+static const struct i2c_algorithm cgbc_i2c_algorithm = {
+	.master_xfer	= cgbc_i2c_xfer,
+	.functionality	= cgbc_i2c_func,
+};
+
+static struct i2c_algo_cgbc_data cgbc_i2c_algo_data[] = {
+	{ .bus_id = CGBC_I2C_PRIMARY_BUS_ID },
+	{ .bus_id = CGBC_I2C_PM_BUS_ID },
+};
+
+static const struct i2c_adapter cgbc_i2c_adapter[] = {
+	{
+		.owner		= THIS_MODULE,
+		.name		= "Congatec General Purpose I2C adapter",
+		.class		= I2C_CLASS_DEPRECATED,
+		.algo		= &cgbc_i2c_algorithm,
+		.algo_data	= &cgbc_i2c_algo_data[0],
+		.nr		= -1,
+	},
+	{
+		.owner		= THIS_MODULE,
+		.name		= "Congatec Power Management I2C adapter",
+		.class		= I2C_CLASS_DEPRECATED,
+		.algo		= &cgbc_i2c_algorithm,
+		.algo_data	= &cgbc_i2c_algo_data[1],
+		.nr		= -1,
+	},
+};
+
+static int cgbc_i2c_probe(struct platform_device *pdev)
+{
+	struct cgbc_device_data *cgbc = dev_get_drvdata(pdev->dev.parent);
+	struct cgbc_i2c_data *i2c;
+	int ret;
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	i2c->cgbc = cgbc;
+	i2c->dev = &pdev->dev;
+	i2c->adap = cgbc_i2c_adapter[pdev->id];
+	i2c->adap.dev.parent = i2c->dev;
+	i2c_set_adapdata(&i2c->adap, i2c);
+	platform_set_drvdata(pdev, i2c);
+
+	ret = cgbc_i2c_set_frequency(&i2c->adap, I2C_MAX_STANDARD_MODE_FREQ);
+	if (ret)
+		return ret;
+
+	return i2c_add_numbered_adapter(&i2c->adap);
+}
+
+static void cgbc_i2c_remove(struct platform_device *pdev)
+{
+	struct cgbc_i2c_data *i2c = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c->adap);
+}
+
+static struct platform_driver cgbc_i2c_driver = {
+	.driver = {
+		.name = "cgbc-i2c",
+	},
+	.probe		= cgbc_i2c_probe,
+	.remove_new	= cgbc_i2c_remove,
+};
+
+module_platform_driver(cgbc_i2c_driver);
+
+MODULE_DESCRIPTION("Congatec Board Controller I2C Driver");
+MODULE_AUTHOR("Thomas Richard <thomas.richard@...tlin.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:cgbc_i2c");

-- 
2.39.5

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