mfd: Add support for STMPE SPI interface

Few STMPE controller can have register interface over SPI or I2C. Current
implementation only supports I2C.

This patch adds support for SPI interface for accessing STMPE's address space.
Signed-off-by: NViresh Kumar <viresh.kumar@st.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

drivers/mfd/Kconfig

@@ -258,7 +258,7 @@ config TWL6040_CORE
 
 config MFD_STMPE
 	bool "Support STMicroelectronics STMPE"
-	depends on I2C=y && GENERIC_HARDIRQS
+	depends on (I2C=y || SPI_MASTER=y) && GENERIC_HARDIRQS
 	select MFD_CORE
 	help
 	  Support for the STMPE family of I/O Expanders from
@@ -288,6 +288,12 @@ config STMPE_I2C
 	default y
 	help
 	  This is used to enable I2C interface of STMPE
+
+config STMPE_SPI
+	bool "STMPE SPI Inteface"
+	depends on SPI_MASTER
+	help
+	  This is used to enable SPI interface of STMPE
 endmenu
 
 config MFD_TC3589X

drivers/mfd/Makefile

@@ -17,6 +17,7 @@ obj-$(CONFIG_MFD_TI_SSP)	+= ti-ssp.o
 
 obj-$(CONFIG_MFD_STMPE)		+= stmpe.o
 obj-$(CONFIG_STMPE_I2C)		+= stmpe-i2c.o
+obj-$(CONFIG_STMPE_SPI)		+= stmpe-spi.o
 obj-$(CONFIG_MFD_TC3589X)	+= tc3589x.o
 obj-$(CONFIG_MFD_T7L66XB)	+= t7l66xb.o tmio_core.o
 obj-$(CONFIG_MFD_TC6387XB)	+= tc6387xb.o tmio_core.o

drivers/mfd/stmpe-spi.c

+/*
+ * ST Microelectronics MFD: stmpe's spi client specific driver
+ *
+ * Copyright (C) ST Microelectronics SA 2011
+ *
+ * License Terms: GNU General Public License, version 2
+ * Author: Viresh Kumar <viresh.kumar@st.com> for ST Microelectronics
+ */
+
+#include <linux/spi/spi.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include "stmpe.h"
+
+#define READ_CMD	(1 << 7)
+
+static int spi_reg_read(struct stmpe *stmpe, u8 reg)
+{
+	struct spi_device *spi = stmpe->client;
+	int status = spi_w8r16(spi, reg | READ_CMD);
+
+	return (status < 0) ? status : status >> 8;
+}
+
+static int spi_reg_write(struct stmpe *stmpe, u8 reg, u8 val)
+{
+	struct spi_device *spi = stmpe->client;
+	u16 cmd = (val << 8) | reg;
+
+	return spi_write(spi, (const u8 *)&cmd, 2);
+}
+
+static int spi_block_read(struct stmpe *stmpe, u8 reg, u8 length, u8 *values)
+{
+	int ret, i;
+
+	for (i = 0; i < length; i++) {
+		ret = spi_reg_read(stmpe, reg + i);
+		if (ret < 0)
+			return ret;
+		*(values + i) = ret;
+	}
+
+	return 0;
+}
+
+static int spi_block_write(struct stmpe *stmpe, u8 reg, u8 length,
+		const u8 *values)
+{
+	int ret = 0, i;
+
+	for (i = length; i > 0; i--, reg++) {
+		ret = spi_reg_write(stmpe, reg, *(values + i - 1));
+		if (ret < 0)
+			return ret;
+	}
+
+	return ret;
+}
+
+static void spi_init(struct stmpe *stmpe)
+{
+	struct spi_device *spi = stmpe->client;
+
+	spi->bits_per_word = 8;
+
+	/* This register is only present for stmpe811 */
+	if (stmpe->variant->id_val == 0x0811)
+		spi_reg_write(stmpe, STMPE811_REG_SPI_CFG, spi->mode);
+
+	if (spi_setup(spi) < 0)
+		dev_dbg(&spi->dev, "spi_setup failed\n");
+}
+
+static struct stmpe_client_info spi_ci = {
+	.read_byte = spi_reg_read,
+	.write_byte = spi_reg_write,
+	.read_block = spi_block_read,
+	.write_block = spi_block_write,
+	.init = spi_init,
+};
+
+static int __devinit
+stmpe_spi_probe(struct spi_device *spi)
+{
+	const struct spi_device_id *id = spi_get_device_id(spi);
+
+	/* don't exceed max specified rate - 1MHz - Limitation of STMPE */
+	if (spi->max_speed_hz > 1000000) {
+		dev_dbg(&spi->dev, "f(sample) %d KHz?\n",
+				(spi->max_speed_hz/1000));
+		return -EINVAL;
+	}
+
+	spi_ci.irq = spi->irq;
+	spi_ci.client = spi;
+	spi_ci.dev = &spi->dev;
+
+	return stmpe_probe(&spi_ci, id->driver_data);
+}
+
+static int __devexit stmpe_spi_remove(struct spi_device *spi)
+{
+	struct stmpe *stmpe = dev_get_drvdata(&spi->dev);
+
+	return stmpe_remove(stmpe);
+}
+
+static const struct spi_device_id stmpe_spi_id[] = {
+	{ "stmpe811", STMPE811 },
+	{ "stmpe1601", STMPE1601 },
+	{ "stmpe2401", STMPE2401 },
+	{ "stmpe2403", STMPE2403 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, stmpe_id);
+
+static struct spi_driver stmpe_spi_driver = {
+	.driver = {
+		.name	= "stmpe-spi",
+		.bus	= &spi_bus_type,
+		.owner	= THIS_MODULE,
+#ifdef CONFIG_PM
+		.pm	= &stmpe_dev_pm_ops,
+#endif
+	},
+	.probe		= stmpe_spi_probe,
+	.remove		= __devexit_p(stmpe_spi_remove),
+	.id_table	= stmpe_spi_id,
+};
+
+static int __init stmpe_init(void)
+{
+	return spi_register_driver(&stmpe_spi_driver);
+}
+subsys_initcall(stmpe_init);
+
+static void __exit stmpe_exit(void)
+{
+	spi_unregister_driver(&stmpe_spi_driver);
+}
+module_exit(stmpe_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("STMPE MFD SPI Interface Driver");
+MODULE_AUTHOR("Viresh Kumar <viresh.kumar@st.com>");

drivers/mfd/stmpe.h

@@ -120,6 +120,7 @@ int stmpe_remove(struct stmpe *stmpe);
 
 #define STMPE811_REG_CHIP_ID		0x00
 #define STMPE811_REG_SYS_CTRL2		0x04
+#define STMPE811_REG_SPI_CFG		0x08
 #define STMPE811_REG_INT_CTRL		0x09
 #define STMPE811_REG_INT_EN		0x0A
 #define STMPE811_REG_INT_STA		0x0B