reset: Add Amlogic Meson Reset Controller

The Amlogic Meson SoCs embeds up to 256 reset lines, add the corresponding
driver.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

drivers/reset/Kconfig

@@ -83,4 +83,12 @@ config RESET_ROCKCHIP
 	  though is that some reset signals, like I2C or MISC reset multiple
 	  devices.
 
+config RESET_MESON
+	bool "Reset controller driver for Amlogic Meson SoCs"
+	depends on DM_RESET && ARCH_MESON
+	imply REGMAP
+	default y
+	help
+	  Support for reset controller on Amlogic Meson SoC.
+
 endmenu

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_RESET_MESON) += reset-meson.o

drivers/reset/reset-meson.c

@@ -0,0 +1,90 @@
+/*
+ * Amlogic Meson Reset Controller driver
+ *
+ * Copyright (c) 2018 BayLibre, SAS.
+ * Author: Neil Armstrong <narmstrong@baylibre.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <reset-uclass.h>
+#include <regmap.h>
+
+#define REG_COUNT	8
+#define BITS_PER_REG	32
+#define LEVEL_OFFSET	0x7c
+
+struct meson_reset_priv {
+	struct regmap *regmap;
+};
+
+static int meson_reset_request(struct reset_ctl *reset_ctl)
+{
+	if (reset_ctl->id > (REG_COUNT * BITS_PER_REG))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int meson_reset_free(struct reset_ctl *reset_ctl)
+{
+	return 0;
+}
+
+static int meson_reset_level(struct reset_ctl *reset_ctl, bool assert)
+{
+	struct meson_reset_priv *priv = dev_get_priv(reset_ctl->dev);
+	uint bank = reset_ctl->id / BITS_PER_REG;
+	uint offset = reset_ctl->id % BITS_PER_REG;
+	uint reg_offset = LEVEL_OFFSET + (bank << 2);
+	uint val;
+
+	regmap_read(priv->regmap, reg_offset, &val);
+	if (assert)
+		val &= ~BIT(offset);
+	else
+		val |= BIT(offset);
+	regmap_write(priv->regmap, reg_offset, val);
+
+	return 0;
+}
+
+static int meson_reset_assert(struct reset_ctl *reset_ctl)
+{
+	return meson_reset_level(reset_ctl, true);
+}
+
+static int meson_reset_deassert(struct reset_ctl *reset_ctl)
+{
+	return meson_reset_level(reset_ctl, false);
+}
+
+struct reset_ops meson_reset_ops = {
+	.request = meson_reset_request,
+	.free = meson_reset_free,
+	.rst_assert = meson_reset_assert,
+	.rst_deassert = meson_reset_deassert,
+};
+
+static const struct udevice_id meson_reset_ids[] = {                          
+	{ .compatible = "amlogic,meson-gxbb-reset" },                                  
+	{ }                                                                     
+};  
+
+static int meson_reset_probe(struct udevice *dev)
+{
+	struct meson_reset_priv *priv = dev_get_priv(dev);
+	
+	return regmap_init_mem(dev, &priv->regmap);
+}
+
+U_BOOT_DRIVER(meson_reset) = {
+	.name = "meson_reset",
+	.id = UCLASS_RESET,
+	.of_match = meson_reset_ids,
+	.probe = meson_reset_probe,
+	.ops = &meson_reset_ops,
+	.priv_auto_alloc_size = sizeof(struct meson_reset_priv),
+};