gpio: Add driver for TI PCF8575 I2C GPIO expander

TI's PCF8575 is a 16-bit I2C GPIO expander.The device features a
16-bit quasi-bidirectional I/O ports. Each quasi-bidirectional I/O can
be used as an input or output without the use of a data-direction
control signal. The I/Os should be high before being used as inputs.
Read the device documentation for more details[1].

This driver is based on pcf857x driver available in Linux v4.7 kernel.
It supports basic reading and writing of gpio pins.

[1] http://www.ti.com/lit/ds/symlink/pcf8575.pdf

Signed-off-by: Vignesh R <vigneshr@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Mugunthan V N <mugunthanvnm@ti.com>

doc/device-tree-bindings/gpio/gpio-pcf857x.txt

@@ -0,0 +1,71 @@
+* PCF857x-compatible I/O expanders
+
+The PCF857x-compatible chips have "quasi-bidirectional" I/O lines that can be
+driven high by a pull-up current source or driven low to ground. This combines
+the direction and output level into a single bit per line, which can't be read
+back. We can't actually know at initialization time whether a line is configured
+(a) as output and driving the signal low/high, or (b) as input and reporting a
+low/high value, without knowing the last value written since the chip came out
+of reset (if any). The only reliable solution for setting up line direction is
+thus to do it explicitly.
+
+Required Properties:
+
+  - compatible: should be one of the following.
+    - "maxim,max7328": For the Maxim MAX7378
+    - "maxim,max7329": For the Maxim MAX7329
+    - "nxp,pca8574": For the NXP PCA8574
+    - "nxp,pca8575": For the NXP PCA8575
+    - "nxp,pca9670": For the NXP PCA9670
+    - "nxp,pca9671": For the NXP PCA9671
+    - "nxp,pca9672": For the NXP PCA9672
+    - "nxp,pca9673": For the NXP PCA9673
+    - "nxp,pca9674": For the NXP PCA9674
+    - "nxp,pca9675": For the NXP PCA9675
+    - "nxp,pcf8574": For the NXP PCF8574
+    - "nxp,pcf8574a": For the NXP PCF8574A
+    - "nxp,pcf8575": For the NXP PCF8575
+    - "ti,tca9554": For the TI TCA9554
+
+  - reg: I2C slave address.
+
+  - gpio-controller: Marks the device node as a gpio controller.
+  - #gpio-cells: Should be 2. The first cell is the GPIO number and the second
+    cell specifies GPIO flags, as defined in <dt-bindings/gpio/gpio.h>. Only the
+    GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags are supported.
+
+Optional Properties:
+
+  - lines-initial-states: Bitmask that specifies the initial state of each
+  line. When a bit is set to zero, the corresponding line will be initialized to
+  the input (pulled-up) state. When the  bit is set to one, the line will be
+  initialized the low-level output state. If the property is not specified
+  all lines will be initialized to the input state.
+
+  The I/O expander can detect input state changes, and thus optionally act as
+  an interrupt controller. When the expander interrupt line is connected all the
+  following properties must be set. For more information please see the
+  interrupt controller device tree bindings documentation available at
+  Documentation/devicetree/bindings/interrupt-controller/interrupts.txt.
+
+  - interrupt-controller: Identifies the node as an interrupt controller.
+  - #interrupt-cells: Number of cells to encode an interrupt source, shall be 2.
+  - interrupt-parent: phandle of the parent interrupt controller.
+  - interrupts: Interrupt specifier for the controllers interrupt.
+
+
+Please refer to gpio.txt in this directory for details of the common GPIO
+bindings used by client devices.
+
+Example: PCF8575 I/O expander node
+
+	pcf8575: gpio@20 {
+		compatible = "nxp,pcf8575";
+		reg = <0x20>;
+		interrupt-parent = <&irqpin2>;
+		interrupts = <3 0>;
+		gpio-controller;
+		#gpio-cells = <2>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+	};

drivers/gpio/Kconfig

@@ -79,6 +79,13 @@ config PM8916_GPIO
 	  Power and reset buttons are placed in "pm8916_key" bank and
           have gpio numbers 0 and 1 respectively.
 
+config PCF8575_GPIO
+	bool "PCF8575 I2C GPIO Expander driver"
+	depends on DM_GPIO && DM_I2C
+	help
+	 Support for PCF8575 I2C 16-bit GPIO expander. Most of these
+	 chips are from NXP and TI.
+
 config ROCKCHIP_GPIO
 	bool "Rockchip GPIO driver"
 	depends on DM_GPIO

drivers/gpio/Makefile

@@ -56,4 +56,5 @@ obj-$(CONFIG_HIKEY_GPIO)	+= hi6220_gpio.o
 obj-$(CONFIG_PIC32_GPIO)	+= pic32_gpio.o
 obj-$(CONFIG_MVEBU_GPIO)	+= mvebu_gpio.o
 obj-$(CONFIG_MSM_GPIO)		+= msm_gpio.o
+obj-$(CONFIG_$(SPL_)PCF8575_GPIO)	+= pcf8575_gpio.o
 obj-$(CONFIG_PM8916_GPIO)	+= pm8916_gpio.o

drivers/gpio/pcf8575_gpio.c

@@ -0,0 +1,180 @@
+/*
+ * PCF8575 I2C GPIO EXPANDER DRIVER
+ *
+ * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * Vignesh R <vigneshr@ti.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ *
+ *
+ * Driver for TI PCF-8575 16-bit I2C gpio expander. Based on
+ * gpio-pcf857x Linux Kernel(v4.7) driver.
+ *
+ * Copyright (C) 2007 David Brownell
+ *
+ */
+
+/*
+ * NOTE: The driver and devicetree bindings are borrowed from Linux
+ * Kernel, but driver does not support all PCF857x devices. It currently
+ * supports PCF8575 16-bit expander by TI and NXP.
+ *
+ * TODO(vigneshr@ti.com):
+ * Support 8 bit PCF857x compatible expanders.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <i2c.h>
+#include <asm-generic/gpio.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct pcf8575_chip {
+	int gpio_count;		/* No. GPIOs supported by the chip */
+
+	/* NOTE:  these chips have strange "quasi-bidirectional" I/O pins.
+	 * We can't actually know whether a pin is configured (a) as output
+	 * and driving the signal low, or (b) as input and reporting a low
+	 * value ... without knowing the last value written since the chip
+	 * came out of reset (if any).  We can't read the latched output.
+	 * In short, the only reliable solution for setting up pin direction
+	 * is to do it explicitly.
+	 *
+	 * Using "out" avoids that trouble.  When left initialized to zero,
+	 * our software copy of the "latch" then matches the chip's all-ones
+	 * reset state.  Otherwise it flags pins to be driven low.
+	 */
+	unsigned int out;	/* software latch */
+	const char *bank_name;	/* Name of the expander bank */
+};
+
+/* Read/Write to 16-bit I/O expander */
+
+static int pcf8575_i2c_write_le16(struct udevice *dev, unsigned int word)
+{
+	struct dm_i2c_chip *chip = dev_get_parent_platdata(dev);
+	u8 buf[2] = { word & 0xff, word >> 8, };
+	int ret;
+
+	ret = dm_i2c_write(dev, 0, buf, 2);
+	if (ret)
+		printf("%s i2c write failed to addr %x\n", __func__,
+		       chip->chip_addr);
+
+	return ret;
+}
+
+static int pcf8575_i2c_read_le16(struct udevice *dev)
+{
+	struct dm_i2c_chip *chip = dev_get_parent_platdata(dev);
+	u8 buf[2];
+	int ret;
+
+	ret = dm_i2c_read(dev, 0, buf, 2);
+	if (ret) {
+		printf("%s i2c read failed from addr %x\n", __func__,
+		       chip->chip_addr);
+		return ret;
+	}
+
+	return (buf[1] << 8) | buf[0];
+}
+
+static int pcf8575_direction_input(struct udevice *dev, unsigned offset)
+{
+	struct pcf8575_chip *plat = dev_get_platdata(dev);
+	int status;
+
+	plat->out |= BIT(offset);
+	status = pcf8575_i2c_write_le16(dev, plat->out);
+
+	return status;
+}
+
+static int pcf8575_direction_output(struct udevice *dev,
+				    unsigned int offset, int value)
+{
+	struct pcf8575_chip *plat = dev_get_platdata(dev);
+	int ret;
+
+	if (value)
+		plat->out |= BIT(offset);
+	else
+		plat->out &= ~BIT(offset);
+
+	ret = pcf8575_i2c_write_le16(dev, plat->out);
+
+	return ret;
+}
+
+static int pcf8575_get_value(struct udevice *dev, unsigned int offset)
+{
+	int             value;
+
+	value = pcf8575_i2c_read_le16(dev);
+
+	return (value < 0) ? value : ((value & BIT(offset)) >> offset);
+}
+
+static int pcf8575_set_value(struct udevice *dev, unsigned int offset,
+			     int value)
+{
+	return pcf8575_direction_output(dev, offset, value);
+}
+
+static int pcf8575_ofdata_platdata(struct udevice *dev)
+{
+	struct pcf8575_chip *plat = dev_get_platdata(dev);
+	struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+
+	int n_latch;
+
+	uc_priv->gpio_count = fdtdec_get_int(gd->fdt_blob, dev->of_offset,
+					     "gpio-count", 16);
+	uc_priv->bank_name = fdt_getprop(gd->fdt_blob, dev->of_offset,
+					 "gpio-bank-name", NULL);
+	if (!uc_priv->bank_name)
+		uc_priv->bank_name = fdt_get_name(gd->fdt_blob,
+						  dev->of_offset, NULL);
+
+	n_latch = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+				  "lines-initial-states", 0);
+	plat->out = ~n_latch;
+
+	return 0;
+}
+
+static int pcf8575_gpio_probe(struct udevice  *dev)
+{
+	struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+
+	debug("%s GPIO controller with %d gpios probed\n",
+	      uc_priv->bank_name, uc_priv->gpio_count);
+
+	return 0;
+}
+
+static const struct dm_gpio_ops pcf8575_gpio_ops = {
+	.direction_input	= pcf8575_direction_input,
+	.direction_output	= pcf8575_direction_output,
+	.get_value		= pcf8575_get_value,
+	.set_value		= pcf8575_set_value,
+};
+
+static const struct udevice_id pcf8575_gpio_ids[] = {
+	{ .compatible = "nxp,pcf8575" },
+	{ .compatible = "ti,pcf8575" },
+	{ }
+};
+
+U_BOOT_DRIVER(gpio_pcf8575) = {
+	.name	= "gpio_pcf8575",
+	.id	= UCLASS_GPIO,
+	.ops	= &pcf8575_gpio_ops,
+	.of_match = pcf8575_gpio_ids,
+	.ofdata_to_platdata = pcf8575_ofdata_platdata,
+	.probe	= pcf8575_gpio_probe,
+	.platdata_auto_alloc_size = sizeof(struct pcf8575_chip),
+};