[U-Boot] [PATCH 1/4] gpio: Add driver for TI PCF8575 I2C GPIO expander
Vignesh R
vigneshr at ti.com
Mon Jul 25 15:10:20 CEST 2016
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 at ti.com>
---
doc/device-tree-bindings/gpio/gpio-pcf857x.txt | 71 +++++++++
drivers/gpio/Kconfig | 7 +
drivers/gpio/Makefile | 1 +
drivers/gpio/pcf8575_gpio.c | 199 +++++++++++++++++++++++++
4 files changed, 278 insertions(+)
create mode 100644 doc/device-tree-bindings/gpio/gpio-pcf857x.txt
create mode 100644 drivers/gpio/pcf8575_gpio.c
diff --git a/doc/device-tree-bindings/gpio/gpio-pcf857x.txt b/doc/device-tree-bindings/gpio/gpio-pcf857x.txt
new file mode 100644
index 000000000000..ada4e2973323
--- /dev/null
+++ b/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 at 20 {
+ compatible = "nxp,pcf8575";
+ reg = <0x20>;
+ interrupt-parent = <&irqpin2>;
+ interrupts = <3 0>;
+ gpio-controller;
+ #gpio-cells = <2>;
+ interrupt-controller;
+ #interrupt-cells = <2>;
+ };
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 73b862dc0b21..1af05358ec76 100644
--- a/drivers/gpio/Kconfig
+++ b/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
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 792d19186aad..8f426c82cdca 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -57,3 +57,4 @@ obj-$(CONFIG_PIC32_GPIO) += pic32_gpio.o
obj-$(CONFIG_MVEBU_GPIO) += mvebu_gpio.o
obj-$(CONFIG_MSM_GPIO) += msm_gpio.o
obj-$(CONFIG_PM8916_GPIO) += pm8916_gpio.o
+obj-$(CONFIG_PCF8575_GPIO) += pcf8575_gpio.o
diff --git a/drivers/gpio/pcf8575_gpio.c b/drivers/gpio/pcf8575_gpio.c
new file mode 100644
index 000000000000..3ca97eee11db
--- /dev/null
+++ b/drivers/gpio/pcf8575_gpio.c
@@ -0,0 +1,199 @@
+/*
+ * PCF8575 I2C GPIO EXPANDER DRIVER
+ *
+ * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * Vignesh R <vigneshr at ti.com>
+ *
+ * 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 version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * 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 16Bit expander by TI and NXP.
+ *
+ * TODO:
+ * 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 */
+ 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);
+ struct i2c_msg msg;
+ u8 buf[2] = { word & 0xff, word >> 8, };
+ int ret;
+
+ msg.addr = chip->chip_addr;
+ msg.buf = buf;
+ msg.flags = 0;
+ msg.len = 2;
+ ret = dm_i2c_xfer(dev, &msg, 1);
+
+ if (ret)
+ printf("%s i2c write failed to addr %x\n", __func__, msg.addr);
+
+ return ret;
+}
+
+static int pcf8575_i2c_read_le16(struct udevice *dev)
+{
+ struct dm_i2c_chip *chip = dev_get_parent_platdata(dev);
+ struct i2c_msg msg;
+ u8 buf[2];
+ int ret;
+
+ msg.addr = chip->chip_addr;
+ msg.buf = buf;
+ msg.flags = I2C_M_RD;
+ msg.len = 2;
+
+ ret = dm_i2c_xfer(dev, &msg, 1);
+ if (ret) {
+ printf("%s i2c read failed to addr %x\n", __func__, msg.addr);
+ return ret;
+ }
+
+ return (msg.buf[1] << 8) | msg.buf[0];
+}
+
+static int pcf8575_direction_input(struct udevice *dev, unsigned offset)
+{
+ struct pcf8575_chip *pc = dev_get_platdata(dev);
+ int status;
+
+ pc->out |= BIT(offset);
+ status = pcf8575_i2c_write_le16(dev, pc->out);
+
+ return status;
+}
+
+static int pcf8575_direction_output(struct udevice *dev,
+ unsigned int offset, int value)
+{
+ struct pcf8575_chip *pc = dev_get_platdata(dev);
+ int ret;
+
+ if (value)
+ pc->out |= BIT(offset);
+ else
+ pc->out &= ~BIT(offset);
+
+ ret = pcf8575_i2c_write_le16(dev, pc->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 *pc = 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);
+
+ /* 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 n_latch 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.
+ */
+
+ n_latch = fdtdec_get_uint(gd->fdt_blob, dev->of_offset,
+ "lines-initial-states", 0);
+ pc->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),
+};
--
2.9.2
More information about the U-Boot
mailing list