[U-Boot] [PATCH] reset: Add generic GPIO reset driver

[Mario Six]

Some reset lines are implemented by toggling the line via a GPIO.

Add a driver to properly drive such reset lines.

Signed-off-by: Mario Six <mario.six at gdsys.cc>
---
 drivers/reset/Kconfig      |   7 ++++
 drivers/reset/Makefile     |   1 +
 drivers/reset/gpio-reset.c | 100 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+)
 create mode 100644 drivers/reset/gpio-reset.c

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index 71a786bab5..b8416fa85a 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -83,4 +83,11 @@ config RESET_ROCKCHIP
 	  though is that some reset signals, like I2C or MISC reset multiple
 	  devices.
 
+config GPIO_RESET
+	bool "Reset driver for GPIO-based reset lines"
+	depends on DM_RESET
+	help
+	  Support a generic reset controller that encapsulates a number of
+	  GPIOs of which each controls a single reset line.
+
 endmenu
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 7d7e080c78..a5d766b183 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o
 obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
 obj-$(CONFIG_AST2500_RESET) += ast2500-reset.o
 obj-$(CONFIG_RESET_ROCKCHIP) += reset-rockchip.o
+obj-$(CONFIG_GPIO_RESET) += gpio-reset.o
diff --git a/drivers/reset/gpio-reset.c b/drivers/reset/gpio-reset.c
new file mode 100644
index 0000000000..52dd47df60
--- /dev/null
+++ b/drivers/reset/gpio-reset.c
@@ -0,0 +1,100 @@
+/*
+ * (C) Copyright 2017
+ * Mario Six, Guntermann & Drunck GmbH, mario.six at gdsys.cc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <reset-uclass.h>
+#include <asm/gpio.h>
+
+struct gpio_reset_priv {
+	struct gpio_desc gpios[16];
+	uint gpio_num;
+};
+
+static int gpio_reset_request(struct reset_ctl *reset_ctl)
+{
+	struct gpio_reset_priv *priv = dev_get_priv(reset_ctl->dev);
+
+	debug("%s(reset_ctl=%p) (dev=%p, id=%lu)\n", __func__, reset_ctl,
+	      reset_ctl->dev, reset_ctl->id);
+
+	/* Reset ID = number of GPIO in list */
+	if (reset_ctl->id >= priv->gpio_num)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int gpio_reset_free(struct reset_ctl *reset_ctl)
+{
+	debug("%s(reset_ctl=%p) (dev=%p, id=%lu)\n", __func__, reset_ctl,
+	      reset_ctl->dev, reset_ctl->id);
+
+	return 0;
+}
+
+static int gpio_reset_assert(struct reset_ctl *reset_ctl)
+{
+	struct gpio_reset_priv *priv = dev_get_priv(reset_ctl->dev);
+
+	debug("%s(reset_ctl=%p) (dev=%p, id=%lu)\n", __func__, reset_ctl,
+	      reset_ctl->dev, reset_ctl->id);
+
+	dm_gpio_set_value(&priv->gpios[reset_ctl->id], 1);
+
+	return 0;
+}
+
+static int gpio_reset_deassert(struct reset_ctl *reset_ctl)
+{
+	struct gpio_reset_priv *priv = dev_get_priv(reset_ctl->dev);
+
+	debug("%s(reset_ctl=%p) (dev=%p, id=%lu)\n", __func__, reset_ctl,
+	      reset_ctl->dev, reset_ctl->id);
+
+	dm_gpio_set_value(&priv->gpios[reset_ctl->id], 0);
+
+	return 0;
+}
+
+struct reset_ops gpio_reset_ops = {
+	.request = gpio_reset_request,
+	.free = gpio_reset_free,
+	.rst_assert = gpio_reset_assert,
+	.rst_deassert = gpio_reset_deassert,
+};
+
+static int gpio_reset_probe(struct udevice *dev)
+{
+	struct gpio_reset_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	debug("%s(dev=%p)\n", __func__, dev);
+
+	ret = gpio_request_list_by_name(dev, "gpios", priv->gpios,
+					ARRAY_SIZE(priv->gpios), GPIOD_IS_OUT);
+	if (ret <= 0)
+		return ret;
+
+	priv->gpio_num = ret;
+
+	return 0;
+}
+
+static const struct udevice_id gpio_reset[] = {
+	{ .compatible = "gpio-reset", },
+	{ /* sentinel */ }
+};
+
+U_BOOT_DRIVER(gpio_reset) = {
+	.name = "gpio_reset",
+	.id = UCLASS_RESET,
+	.of_match = gpio_reset,
+	.probe = gpio_reset_probe,
+	.ops = &gpio_reset_ops,
+	.priv_auto_alloc_size = sizeof(struct gpio_reset_priv),
+};
-- 
2.16.1