dm: gpio: introduce 74x164 driver

Introduce driver to support "fairchild,74hc595" devices.
1. Take linux drivers/drivers/gpio/gpio-74x164.c as reference.
2. Following the naming used in Linux driver with gen_7x164 as the prefix.
3. Enable CONFIG_DM_74X164 to use this driver.
4. Follow Documentation/devicetree/bindings/gpio/gpio-74x164.txt to add device
   nodes
5. Tested on i.MX6 UltraLite with 74LV595 using gpio command and oscillograph.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Chin Liang See <clsee@altera.com>
Cc: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/gpio/74x164_gpio.c

@@ -0,0 +1,193 @@
+/*
+ * Take drivers/gpio/gpio-74x164.c as reference.
+ *
+ * 74Hx164 - Generic serial-in/parallel-out 8-bits shift register GPIO driver
+ *
+ * Copyright (C) 2016 Peng Fan <van.freenix@gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ *
+ */
+
+#include <common.h>
+#include <errno.h>
+#include <dm.h>
+#include <fdtdec.h>
+#include <malloc.h>
+#include <asm/gpio.h>
+#include <asm/io.h>
+#include <dt-bindings/gpio/gpio.h>
+#include <spi.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/*
+ * struct gen_74x164_chip - Data for 74Hx164
+ *
+ * @oe: OE pin
+ * @nregs: number of registers
+ * @buffer: buffer for chained chips
+ */
+#define GEN_74X164_NUMBER_GPIOS 8
+
+struct gen_74x164_priv {
+	struct gpio_desc oe;
+	u32 nregs;
+	/*
+	 * Since the nregs are chained, every byte sent will make
+	 * the previous byte shift to the next register in the
+	 * chain. Thus, the first byte sent will end up in the last
+	 * register at the end of the transfer. So, to have a logical
+	 * numbering, store the bytes in reverse order.
+	 */
+	u8 *buffer;
+};
+
+static int gen_74x164_write_conf(struct udevice *dev)
+{
+	struct gen_74x164_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	ret = dm_spi_claim_bus(dev);
+	if (ret)
+		return ret;
+
+	ret = dm_spi_xfer(dev, priv->nregs * 8, priv->buffer, NULL,
+			  SPI_XFER_BEGIN | SPI_XFER_END);
+
+	dm_spi_release_bus(dev);
+
+	return ret;
+}
+
+static int gen_74x164_get_value(struct udevice *dev, unsigned offset)
+{
+	struct gen_74x164_priv *priv = dev_get_priv(dev);
+	uint bank = priv->nregs - 1 - offset / 8;
+	uint pin = offset % 8;
+
+	return (priv->buffer[bank] >> pin) & 0x1;
+}
+
+static int gen_74x164_set_value(struct udevice *dev, unsigned offset,
+				int value)
+{
+	struct gen_74x164_priv *priv = dev_get_priv(dev);
+	uint bank = priv->nregs - 1 - offset / 8;
+	uint pin = offset % 8;
+	int ret;
+
+	if (value)
+		priv->buffer[bank] |= 1 << pin;
+	else
+		priv->buffer[bank] &= ~(1 << pin);
+
+	ret = gen_74x164_write_conf(dev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int gen_74x164_direction_input(struct udevice *dev, unsigned offset)
+{
+	return -ENOSYS;
+}
+
+static int gen_74x164_direction_output(struct udevice *dev, unsigned offset,
+				      int value)
+{
+	return gen_74x164_set_value(dev, offset, value);
+}
+
+static int gen_74x164_get_function(struct udevice *dev, unsigned offset)
+{
+	return GPIOF_OUTPUT;
+}
+
+static int gen_74x164_xlate(struct udevice *dev, struct gpio_desc *desc,
+			    struct fdtdec_phandle_args *args)
+{
+	desc->offset = args->args[0];
+	desc->flags = args->args[1] & GPIO_ACTIVE_LOW ? GPIOD_ACTIVE_LOW : 0;
+
+	return 0;
+}
+
+static const struct dm_gpio_ops gen_74x164_ops = {
+	.direction_input	= gen_74x164_direction_input,
+	.direction_output	= gen_74x164_direction_output,
+	.get_value		= gen_74x164_get_value,
+	.set_value		= gen_74x164_set_value,
+	.get_function		= gen_74x164_get_function,
+	.xlate			= gen_74x164_xlate,
+};
+
+static int gen_74x164_probe(struct udevice *dev)
+{
+	struct gen_74x164_priv *priv = dev_get_priv(dev);
+	struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+	char *str, name[32];
+	int ret;
+	const void *fdt = gd->fdt_blob;
+	int node = dev->of_offset;
+
+	snprintf(name, sizeof(name), "%s_", dev->name);
+	str = strdup(name);
+	if (!str)
+		return -ENOMEM;
+
+	/*
+	 * See Linux kernel:
+	 * Documentation/devicetree/bindings/gpio/gpio-74x164.txt
+	 */
+	priv->nregs = fdtdec_get_int(fdt, node, "registers-number", 1);
+	priv->buffer = calloc(priv->nregs, sizeof(u8));
+	if (!priv->buffer) {
+		ret = -ENOMEM;
+		goto free_str;
+	}
+
+	ret = fdtdec_get_byte_array(fdt, node, "registers-default",
+				    priv->buffer, priv->nregs);
+	if (ret)
+		dev_dbg(dev, "No registers-default property\n");
+
+	ret = gpio_request_by_name(dev, "oe-gpios", 0, &priv->oe,
+				   GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE);
+	if (ret) {
+		dev_err(dev, "No oe-pins property\n");
+		goto free_buf;
+	}
+
+	uc_priv->bank_name = str;
+	uc_priv->gpio_count = priv->nregs * 8;
+
+	ret = gen_74x164_write_conf(dev);
+	if (ret)
+		goto free_buf;
+
+	dev_dbg(dev, "%s is ready\n", dev->name);
+
+	return 0;
+
+free_buf:
+	free(priv->buffer);
+free_str:
+	free(str);
+	return ret;
+}
+
+static const struct udevice_id gen_74x164_ids[] = {
+	{ .compatible = "fairchild,74hc595" },
+	{ }
+};
+
+U_BOOT_DRIVER(74x164) = {
+	.name		= "74x164",
+	.id		= UCLASS_GPIO,
+	.ops		= &gen_74x164_ops,
+	.probe		= gen_74x164_probe,
+	.priv_auto_alloc_size = sizeof(struct gen_74x164_priv),
+	.of_match	= gen_74x164_ids,
+};

drivers/gpio/Kconfig

@@ -143,6 +143,14 @@ config ZYNQ_GPIO
 	help
 	  Supports GPIO access on Zynq SoC.
 
+config DM_74X164
+	bool "74x164 serial-in/parallel-out 8-bits shift register"
+	depends on DM_GPIO
+	help
+	  Driver for 74x164 compatible serial-in/parallel-out 8-outputs
+	  shift registers, such as 74lv165, 74hc595.
+	  This driver can be used to provide access to more gpio outputs.
+
 config DM_PCA953X
 	bool "PCA95[357]x, PCA9698, TCA64xx, and MAX7310 I/O ports"
 	depends on DM_GPIO

drivers/gpio/Makefile

@@ -12,6 +12,7 @@ endif
 obj-$(CONFIG_DM_GPIO)		+= gpio-uclass.o
 
 obj-$(CONFIG_DM_PCA953X)	+= pca953x_gpio.o
+obj-$(CONFIG_DM_74X164)		+= 74x164_gpio.o
 
 obj-$(CONFIG_AT91_GPIO)	+= at91_gpio.o
 obj-$(CONFIG_ATMEL_PIO4)	+= atmel_pio4.o