sifive: reset: add DM based reset driver for SiFive SoC's

PRCI module within SiFive SoC's has register with which we can
reset the sub-systems within the SoC. The resets to DDR and ethernet
sub systems within FU540-C000 SoC are active low, and are hold low
by default on power-up. Currently these are directly asserted within
prci driver via register read/write.
With the DM based reset driver support here, we bind the reset
driver with clock (prci) driver and assert the reset signals of
both sub-system's appropriately.

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
Reviewed-by: Pragnesh Patel <Pragnesh.patel@sifive.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Tested-by: Bin Meng <bin.meng@windriver.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/drivers/reset/reset-sifive.c b/drivers/reset/reset-sifive.c
new file mode 100644
index 0000000000..527757f853
--- /dev/null
+++ b/drivers/reset/reset-sifive.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 Sifive, Inc.
+ * Author: Sagar Kadam <sagar.kadam@sifive.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <reset-uclass.h>
+#include <asm/io.h>
+#include <dm/device_compat.h>
+#include <dm/lists.h>
+#include <linux/bitops.h>
+
+#define PRCI_RESETREG_OFFSET 0x28
+
+struct sifive_reset_priv {
+	void *base;
+	/* number of reset signals */
+	int nr_reset;
+};
+
+static int sifive_rst_trigger(struct reset_ctl *rst, bool level)
+{
+	struct sifive_reset_priv *priv = dev_get_priv(rst->dev);
+	int id = rst->id;
+	int regval = readl(priv->base + PRCI_RESETREG_OFFSET);
+
+	/* Derive bitposition from rst id */
+	if (level)
+		/* Reset deassert */
+		regval |= BIT(id);
+	else
+		/* Reset assert */
+		regval &= ~BIT(id);
+
+	writel(regval, priv->base + PRCI_RESETREG_OFFSET);
+
+	return 0;
+}
+
+static int sifive_reset_assert(struct reset_ctl *rst)
+{
+	return sifive_rst_trigger(rst, false);
+}
+
+static int sifive_reset_deassert(struct reset_ctl *rst)
+{
+	return sifive_rst_trigger(rst, true);
+}
+
+static int sifive_reset_request(struct reset_ctl *rst)
+{
+	struct sifive_reset_priv *priv = dev_get_priv(rst->dev);
+
+	debug("%s(rst=%p) (dev=%p, id=%lu) (nr_reset=%d)\n", __func__,
+	      rst, rst->dev, rst->id, priv->nr_reset);
+
+	if (rst->id > priv->nr_reset)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int sifive_reset_free(struct reset_ctl *rst)
+{
+	struct sifive_reset_priv *priv = dev_get_priv(rst->dev);
+
+	debug("%s(rst=%p) (dev=%p, id=%lu) (nr_reset=%d)\n", __func__,
+	      rst, rst->dev, rst->id, priv->nr_reset);
+
+	return 0;
+}
+
+static int sifive_reset_probe(struct udevice *dev)
+{
+	struct sifive_reset_priv *priv = dev_get_priv(dev);
+
+	priv->base = dev_remap_addr(dev);
+	if (!priv->base)
+		return -ENOMEM;
+
+	return 0;
+}
+
+int sifive_reset_bind(struct udevice *dev, ulong count)
+{
+	struct udevice *rst_dev;
+	struct sifive_reset_priv *priv;
+	int ret;
+
+	ret = device_bind_driver_to_node(dev, "sifive-reset", "reset",
+					 dev_ofnode(dev), &rst_dev);
+	if (ret) {
+		dev_err(dev, "failed to bind sifive_reset driver (ret=%d)\n", ret);
+		return ret;
+	}
+	priv = malloc(sizeof(struct sifive_reset_priv));
+	priv->nr_reset = count;
+	rst_dev->priv = priv;
+
+	return 0;
+}
+
+const struct reset_ops sifive_reset_ops = {
+	.request = sifive_reset_request,
+	.rfree = sifive_reset_free,
+	.rst_assert = sifive_reset_assert,
+	.rst_deassert = sifive_reset_deassert,
+};
+
+U_BOOT_DRIVER(sifive_reset) = {
+	.name		= "sifive-reset",
+	.id		= UCLASS_RESET,
+	.ops		= &sifive_reset_ops,
+	.probe		= sifive_reset_probe,
+	.priv_auto_alloc_size = sizeof(struct sifive_reset_priv),
+};