[U-Boot] [RFC PATCH 04/13] reset: add driver for generic reset controllers

[Andre Przywara]

From: Amit Singh Tomar <amittomer25 at gmail.com>

The simplest and most generic form of a reset controller just exposes
multiple MMIO registers, where each bit toggles a separate reset line.
Add a generic driver to describe this kind of reset controller.

This is used on the Nexell S5P6818, for instance, but also by other
SoCs.

Signed-off-by: Amit Singh Tomar <amittomer25 at gmail.com>
[Andre: make more generic, let it cover multiple registers, slight rework]
Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
 drivers/reset/Kconfig         |   6 +++
 drivers/reset/Makefile        |   1 +
 drivers/reset/reset-generic.c | 111 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+)
 create mode 100644 drivers/reset/reset-generic.c

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index ce46e2752c..3032b0064c 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -12,6 +12,12 @@ config DM_RESET
 	  although driving such reset isgnals using GPIOs may be more
 	  appropriate in this case.
 
+config GENERIC_RESET
+        bool "Generic Reset controller driver"
+        depends on DM_RESET
+        help
+          Support Generic reset controller.
+
 config SANDBOX_RESET
 	bool "Enable the sandbox reset test driver"
 	depends on DM_MAILBOX && SANDBOX
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 252cefeed5..81680837ef 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -12,3 +12,4 @@ obj-$(CONFIG_TEGRA186_RESET) += tegra186-reset.o
 obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o
 obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
 obj-$(CONFIG_AST2500_RESET) += ast2500-reset.o
+obj-$(CONFIG_GENERIC_RESET) += reset-generic.o
diff --git a/drivers/reset/reset-generic.c b/drivers/reset/reset-generic.c
new file mode 100644
index 0000000000..0a7740202d
--- /dev/null
+++ b/drivers/reset/reset-generic.c
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2017 Amit Singh Tomar <amittomer25 at gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <reset-uclass.h>
+#include <linux/bitops.h>
+#include <linux/io.h>
+#include <linux/sizes.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct generic_reset_priv {
+	void __iomem *membase;
+	int max_reset;
+};
+
+#define BITS_PER_BYTE 8
+static int generic_reset_toggle(struct reset_ctl *rst, bool assert)
+{
+	struct generic_reset_priv *priv = dev_get_priv(rst->dev);
+	int reg_width = sizeof(u32);
+	int bank, offset;
+	u32 reg;
+
+	if (rst->id >= priv->max_reset)
+		return -EINVAL;
+
+	bank = rst->id / (reg_width * BITS_PER_BYTE);
+	offset = rst->id % (reg_width * BITS_PER_BYTE);
+
+	reg = readl(priv->membase + (bank * reg_width));
+	if (assert)
+		writel(reg & ~BIT(offset), priv->membase + (bank * reg_width));
+	else
+		writel(reg | BIT(offset), priv->membase + (bank * reg_width));
+
+	return 0;
+}
+
+static int generic_reset_assert(struct reset_ctl *rst)
+{
+	return generic_reset_toggle(rst, true);
+}
+
+static int generic_reset_deassert(struct reset_ctl *rst)
+{
+	return generic_reset_toggle(rst, false);
+}
+
+static int generic_reset_free(struct reset_ctl *rst)
+{
+	return 0;
+}
+
+static int generic_reset_request(struct reset_ctl *rst)
+{
+	struct generic_reset_priv *priv = dev_get_priv(rst->dev);
+
+	if (rst->id >= priv->max_reset)
+		return -EINVAL;
+
+	return generic_reset_assert(rst);
+}
+
+struct reset_ops generic_reset_reset_ops = {
+	.free = generic_reset_free,
+	.request = generic_reset_request,
+	.rst_assert = generic_reset_assert,
+	.rst_deassert = generic_reset_deassert,
+};
+
+static const struct udevice_id generic_reset_ids[] = {
+	{ .compatible = "generic-reset" },
+	{ .compatible = "nexell,s5p6818-reset" },
+	{ }
+};
+
+static int generic_reset_probe(struct udevice *dev)
+{
+	struct generic_reset_priv *priv = dev_get_priv(dev);
+	fdt_addr_t addr;
+	fdt_size_t size;
+
+	addr = devfdt_get_addr_size_index(dev, 0, &size);
+	if (addr == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	priv->max_reset = dev_read_u32_default(dev, "num-resets", -1);
+	if (priv->max_reset == -1)
+		priv->max_reset = size * BITS_PER_BYTE;
+
+	priv->membase = devm_ioremap(dev, addr, size);
+	if (!priv->membase)
+		return -EFAULT;
+
+	return 0;
+}
+
+U_BOOT_DRIVER(generic_reset) = {
+	.name = "generic_reset",
+	.id = UCLASS_RESET,
+	.of_match = generic_reset_ids,
+	.ops = &generic_reset_reset_ops,
+	.probe = generic_reset_probe,
+	.priv_auto_alloc_size = sizeof(struct generic_reset_priv),
+};
-- 
2.14.1