spi: Master driver for NXP SC18IS602/603

This driver adds support for NXP SC18IS602/603 I2C to SPI bus bridge.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

Documentation/devicetree/bindings/spi/spi-sc18is602.txt

+NXP SC18IS602/SCIS603
+
+Required properties:
+	- compatible : Should be one of
+		"nxp,sc18is602"
+		"nxp,sc18is602b"
+		"nxp,sc18is603"
+	- reg: I2C bus address
+
+Optional properties:
+	- clock-frequency : external oscillator clock frequency. If not
+	  specified, the SC18IS602 default frequency (7372000) will be used.
+
+The clock-frequency property is relevant and needed only if the chip has an
+external oscillator (SC18IS603).
+
+Example:
+
+	sc18is603@28 {
+		compatible = "nxp,sc18is603";
+		reg = <0x28>;
+		clock-frequency = <14744000>;
+	}

Documentation/spi/spi-sc18is602

+Kernel driver spi-sc18is602
+===========================
+
+Supported chips:
+  * NXP SI18IS602/602B/603
+    Datasheet: http://www.nxp.com/documents/data_sheet/SC18IS602_602B_603.pdf
+
+Author:
+        Guenter Roeck <linux@roeck-us.net>
+
+
+Description
+-----------
+
+This driver provides connects a NXP SC18IS602/603 I2C-bus to SPI bridge to the
+kernel's SPI core subsystem.
+
+The driver does not probe for supported chips, since the SI18IS602/603 does not
+support Chip ID registers. You will have to instantiate the devices explicitly.
+Please see Documentation/i2c/instantiating-devices for details.
+
+
+Usage Notes
+-----------
+
+This driver requires the I2C adapter driver to support raw I2C messages. I2C
+adapter drivers which can only handle the SMBus protocol are not supported.
+
+The maximum SPI message size supported by SC18IS602/603 is 200 bytes. Attempts
+to initiate longer transfers will fail with -EINVAL. EEPROM read operations and
+similar large accesses have to be split into multiple chunks of no more than
+200 bytes per SPI message (128 bytes of data per message is recommended). This
+means that programs such as "cp" or "od", which automatically use large block
+sizes to access a device, can not be used directly to read data from EEPROM.
+Programs such as dd, where the block size can be specified, should be used
+instead.

drivers/spi/Kconfig

@@ -325,6 +325,12 @@ config SPI_S3C64XX
 	help
 	  SPI driver for Samsung S3C64XX and newer SoCs.
 
+config SPI_SC18IS602
+	tristate "NXP SC18IS602/602B/603 I2C to SPI bridge"
+	depends on I2C
+	help
+	  SPI driver for NXP SC18IS602/602B/603 I2C to SPI bridge.
+
 config SPI_SH_MSIOF
 	tristate "SuperH MSIOF SPI controller"
 	depends on SUPERH && HAVE_CLK

drivers/spi/Makefile

@@ -51,6 +51,7 @@ obj-$(CONFIG_SPI_S3C24XX)		+= spi-s3c24xx-hw.o
 spi-s3c24xx-hw-y			:= spi-s3c24xx.o
 spi-s3c24xx-hw-$(CONFIG_SPI_S3C24XX_FIQ) += spi-s3c24xx-fiq.o
 obj-$(CONFIG_SPI_S3C64XX)		+= spi-s3c64xx.o
+obj-$(CONFIG_SPI_SC18IS602)		+= spi-sc18is602.o
 obj-$(CONFIG_SPI_SH)			+= spi-sh.o
 obj-$(CONFIG_SPI_SH_HSPI)		+= spi-sh-hspi.o
 obj-$(CONFIG_SPI_SH_MSIOF)		+= spi-sh-msiof.o

drivers/spi/spi-sc18is602.c

+/*
+ * NXP SC18IS602/603 SPI driver
+ *
+ * Copyright (C) Guenter Roeck <linux@roeck-us.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/pm_runtime.h>
+#include <linux/of.h>
+#include <linux/platform_data/sc18is602.h>
+
+enum chips { sc18is602, sc18is602b, sc18is603 };
+
+#define SC18IS602_BUFSIZ		200
+#define SC18IS602_CLOCK			7372000
+
+#define SC18IS602_MODE_CPHA		BIT(2)
+#define SC18IS602_MODE_CPOL		BIT(3)
+#define SC18IS602_MODE_LSB_FIRST	BIT(5)
+#define SC18IS602_MODE_CLOCK_DIV_4	0x0
+#define SC18IS602_MODE_CLOCK_DIV_16	0x1
+#define SC18IS602_MODE_CLOCK_DIV_64	0x2
+#define SC18IS602_MODE_CLOCK_DIV_128	0x3
+
+struct sc18is602 {
+	struct spi_master	*master;
+	struct device		*dev;
+	u8			ctrl;
+	u32			freq;
+	u32			speed;
+
+	/* I2C data */
+	struct i2c_client	*client;
+	enum chips		id;
+	u8			buffer[SC18IS602_BUFSIZ + 1];
+	int			tlen;	/* Data queued for tx in buffer */
+	int			rindex;	/* Receive data index in buffer */
+};
+
+static int sc18is602_wait_ready(struct sc18is602 *hw, int len)
+{
+	int i, err;
+	int usecs = 1000000 * len / hw->speed + 1;
+	u8 dummy[1];
+
+	for (i = 0; i < 10; i++) {
+		err = i2c_master_recv(hw->client, dummy, 1);
+		if (err >= 0)
+			return 0;
+		usleep_range(usecs, usecs * 2);
+	}
+	return -ETIMEDOUT;
+}
+
+static int sc18is602_txrx(struct sc18is602 *hw, struct spi_message *msg,
+			  struct spi_transfer *t, bool do_transfer)
+{
+	unsigned int len = t->len;
+	int ret;
+
+	if (hw->tlen == 0) {
+		/* First byte (I2C command) is chip select */
+		hw->buffer[0] = 1 << msg->spi->chip_select;
+		hw->tlen = 1;
+		hw->rindex = 0;
+	}
+	/*
+	 * We can not immediately send data to the chip, since each I2C message
+	 * resembles a full SPI message (from CS active to CS inactive).
+	 * Enqueue messages up to the first read or until do_transfer is true.
+	 */
+	if (t->tx_buf) {
+		memcpy(&hw->buffer[hw->tlen], t->tx_buf, len);
+		hw->tlen += len;
+		if (t->rx_buf)
+			do_transfer = true;
+		else
+			hw->rindex = hw->tlen - 1;
+	} else if (t->rx_buf) {
+		/*
+		 * For receive-only transfers we still need to perform a dummy
+		 * write to receive data from the SPI chip.
+		 * Read data starts at the end of transmit data (minus 1 to
+		 * account for CS).
+		 */
+		hw->rindex = hw->tlen - 1;
+		memset(&hw->buffer[hw->tlen], 0, len);
+		hw->tlen += len;
+		do_transfer = true;
+	}
+
+	if (do_transfer && hw->tlen > 1) {
+		ret = sc18is602_wait_ready(hw, SC18IS602_BUFSIZ);
+		if (ret < 0)
+			return ret;
+		ret = i2c_master_send(hw->client, hw->buffer, hw->tlen);
+		if (ret < 0)
+			return ret;
+		if (ret != hw->tlen)
+			return -EIO;
+
+		if (t->rx_buf) {
+			int rlen = hw->rindex + len;
+
+			ret = sc18is602_wait_ready(hw, hw->tlen);
+			if (ret < 0)
+				return ret;
+			ret = i2c_master_recv(hw->client, hw->buffer, rlen);
+			if (ret < 0)
+				return ret;
+			if (ret != rlen)
+				return -EIO;
+			memcpy(t->rx_buf, &hw->buffer[hw->rindex], len);
+		}
+		hw->tlen = 0;
+	}
+	return len;
+}
+
+static int sc18is602_setup_transfer(struct sc18is602 *hw, u32 hz, u8 mode)
+{
+	u8 ctrl = 0;
+	int ret;
+
+	if (mode & SPI_CPHA)
+		ctrl |= SC18IS602_MODE_CPHA;
+	if (mode & SPI_CPOL)
+		ctrl |= SC18IS602_MODE_CPOL;
+	if (mode & SPI_LSB_FIRST)
+		ctrl |= SC18IS602_MODE_LSB_FIRST;
+
+	/* Find the closest clock speed */
+	if (hz >= hw->freq / 4) {
+		ctrl |= SC18IS602_MODE_CLOCK_DIV_4;
+		hw->speed = hw->freq / 4;
+	} else if (hz >= hw->freq / 16) {
+		ctrl |= SC18IS602_MODE_CLOCK_DIV_16;
+		hw->speed = hw->freq / 16;
+	} else if (hz >= hw->freq / 64) {
+		ctrl |= SC18IS602_MODE_CLOCK_DIV_64;
+		hw->speed = hw->freq / 64;
+	} else {
+		ctrl |= SC18IS602_MODE_CLOCK_DIV_128;
+		hw->speed = hw->freq / 128;
+	}
+
+	/*
+	 * Don't do anything if the control value did not change. The initial
+	 * value of 0xff for hw->ctrl ensures that the correct mode will be set
+	 * with the first call to this function.
+	 */
+	if (ctrl == hw->ctrl)
+		return 0;
+
+	ret = i2c_smbus_write_byte_data(hw->client, 0xf0, ctrl);
+	if (ret < 0)
+		return ret;
+
+	hw->ctrl = ctrl;
+
+	return 0;
+}
+
+static int sc18is602_check_transfer(struct spi_device *spi,
+				    struct spi_transfer *t, int tlen)
+{
+	int bpw;
+	uint32_t hz;
+
+	if (t && t->len + tlen > SC18IS602_BUFSIZ)
+		return -EINVAL;
+
+	bpw = spi->bits_per_word;
+	if (t && t->bits_per_word)
+		bpw = t->bits_per_word;
+	if (bpw != 8)
+		return -EINVAL;
+
+	hz = spi->max_speed_hz;
+	if (t && t->speed_hz)
+		hz = t->speed_hz;
+	if (hz == 0)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int sc18is602_transfer_one(struct spi_master *master,
+				  struct spi_message *m)
+{
+	struct sc18is602 *hw = spi_master_get_devdata(master);
+	struct spi_device *spi = m->spi;
+	struct spi_transfer *t;
+	int status = 0;
+
+	/* SC18IS602 does not support CS2 */
+	if (hw->id == sc18is602 && spi->chip_select == 2) {
+		status = -ENXIO;
+		goto error;
+	}
+
+	hw->tlen = 0;
+	list_for_each_entry(t, &m->transfers, transfer_list) {
+		u32 hz = t->speed_hz ? : spi->max_speed_hz;
+		bool do_transfer;
+
+		status = sc18is602_check_transfer(spi, t, hw->tlen);
+		if (status < 0)
+			break;
+
+		status = sc18is602_setup_transfer(hw, hz, spi->mode);
+		if (status < 0)
+			break;
+
+		do_transfer = t->cs_change || list_is_last(&t->transfer_list,
+							   &m->transfers);
+
+		if (t->len) {
+			status = sc18is602_txrx(hw, m, t, do_transfer);
+			if (status < 0)
+				break;
+			m->actual_length += status;
+		}
+		status = 0;
+
+		if (t->delay_usecs)
+			udelay(t->delay_usecs);
+	}
+error:
+	m->status = status;
+	spi_finalize_current_message(master);
+
+	return status;
+}
+
+static int sc18is602_setup(struct spi_device *spi)
+{
+	if (!spi->bits_per_word)
+		spi->bits_per_word = 8;
+
+	if (spi->mode & ~(SPI_CPHA | SPI_CPOL | SPI_LSB_FIRST))
+		return -EINVAL;
+
+	return sc18is602_check_transfer(spi, NULL, 0);
+}
+
+static int sc18is602_probe(struct i2c_client *client,
+			   const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct device_node *np = dev->of_node;
+	struct sc18is602_platform_data *pdata = dev_get_platdata(dev);
+	struct sc18is602 *hw;
+	struct spi_master *master;
+	int error;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
+				     I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
+		return -ENODEV;
+
+	master = spi_alloc_master(dev, sizeof(struct sc18is602));
+	if (!master)
+		return -ENOMEM;
+
+	hw = spi_master_get_devdata(master);
+	i2c_set_clientdata(client, hw);
+
+	hw->master = master;
+	hw->client = client;
+	hw->dev = dev;
+	hw->ctrl = 0xff;
+
+	hw->id = id->driver_data;
+
+	switch (hw->id) {
+	case sc18is602:
+	case sc18is602b:
+		master->num_chipselect = 4;
+		hw->freq = SC18IS602_CLOCK;
+		break;
+	case sc18is603:
+		master->num_chipselect = 2;
+		if (pdata) {
+			hw->freq = pdata->clock_frequency;
+		} else {
+			const __be32 *val;
+			int len;
+
+			val = of_get_property(np, "clock-frequency", &len);
+			if (val && len >= sizeof(__be32))
+				hw->freq = be32_to_cpup(val);
+		}
+		if (!hw->freq)
+			hw->freq = SC18IS602_CLOCK;
+		break;
+	}
+	master->bus_num = client->adapter->nr;
+	master->mode_bits = SPI_CPHA | SPI_CPOL | SPI_LSB_FIRST;
+	master->setup = sc18is602_setup;
+	master->transfer_one_message = sc18is602_transfer_one;
+	master->dev.of_node = np;
+
+	error = spi_register_master(master);
+	if (error)
+		goto error_reg;
+
+	return 0;
+
+error_reg:
+	spi_master_put(master);
+	return error;
+}
+
+static int sc18is602_remove(struct i2c_client *client)
+{
+	struct sc18is602 *hw = i2c_get_clientdata(client);
+	struct spi_master *master = hw->master;
+
+	spi_unregister_master(master);
+
+	return 0;
+}
+
+static const struct i2c_device_id sc18is602_id[] = {
+	{ "sc18is602", sc18is602 },
+	{ "sc18is602b", sc18is602b },
+	{ "sc18is603", sc18is603 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sc18is602_id);
+
+static struct i2c_driver sc18is602_driver = {
+	.driver = {
+		.name = "sc18is602",
+	},
+	.probe = sc18is602_probe,
+	.remove = sc18is602_remove,
+	.id_table = sc18is602_id,
+};
+
+module_i2c_driver(sc18is602_driver);
+
+MODULE_DESCRIPTION("SC18IC602/603 SPI Master Driver");
+MODULE_AUTHOR("Guenter Roeck");
+MODULE_LICENSE("GPL");

include/linux/platform_data/sc18is602.h

+/*
+ * Platform data for NXP SC18IS602/603
+ *
+ * Copyright (C) 2012 Guenter Roeck <linux@roeck-us.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * For further information, see the Documentation/spi/sc18is602 file.
+ */
+
+/**
+ * struct sc18is602_platform_data - sc18is602 info
+ * @clock_frequency		SC18IS603 oscillator frequency
+ */
+struct sc18is602_platform_data {
+	u32 clock_frequency;
+};