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>

arch/riscv/include/asm/arch-fu540/reset.h

@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2020 SiFive, Inc.
+ *
+ * Author: Sagar Kadam <sagar.kadam@sifive.com>
+ */
+
+#ifndef __RESET_SIFIVE_H
+#define __RESET_SIFIVE_H
+
+int sifive_reset_bind(struct udevice *dev, ulong count);
+
+#endif

drivers/clk/sifive/fu540-prci.c

@@ -30,11 +30,15 @@
 
 #include <common.h>
 #include <asm/io.h>
+#include <asm/arch/reset.h>
 #include <clk-uclass.h>
 #include <clk.h>
 #include <div64.h>
 #include <dm.h>
 #include <errno.h>
+#include <reset-uclass.h>
+#include <dm/device.h>
+#include <dm/uclass.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 
@@ -132,6 +136,7 @@
 
 /* DEVICESRESETREG */
 #define PRCI_DEVICESRESETREG_OFFSET	0x28
+#define PRCI_DEVICERESETCNT 5
 
 #define PRCI_DEVICESRESETREG_DDR_CTRL_RST_N_MASK \
 			(0x1 << PRCI_RST_DDR_CTRL_N)
@@ -525,6 +530,41 @@ static const struct __prci_clock_ops sifive_fu540_prci_tlclksel_clk_ops = {
 	.recalc_rate = sifive_fu540_prci_tlclksel_recalc_rate,
 };
 
+static int __prci_consumer_reset(const char *rst_name, bool trigger)
+{
+	struct udevice *dev;
+	struct reset_ctl rst_sig;
+	int ret;
+
+	ret = uclass_get_device_by_driver(UCLASS_RESET,
+					  DM_GET_DRIVER(sifive_reset),
+					  &dev);
+	if (ret) {
+		dev_err(dev, "Reset driver not found: %d\n", ret);
+		return ret;
+	}
+
+	ret = reset_get_by_name(dev, rst_name, &rst_sig);
+	if (ret) {
+		dev_err(dev, "failed to get %s reset\n", rst_name);
+		return ret;
+	}
+
+	if (reset_valid(&rst_sig)) {
+		if (trigger)
+			ret = reset_deassert(&rst_sig);
+		else
+			ret = reset_assert(&rst_sig);
+		if (ret) {
+			dev_err(dev, "failed to trigger reset id = %ld\n",
+				rst_sig.id);
+			return ret;
+		}
+	}
+
+	return ret;
+}
+
 /**
  * __prci_ddr_release_reset() - Release DDR reset
  * @pd: struct __prci_data * for the PRCI containing the DDRCLK mux reg
@@ -532,19 +572,20 @@ static const struct __prci_clock_ops sifive_fu540_prci_tlclksel_clk_ops = {
  */
 static void __prci_ddr_release_reset(struct __prci_data *pd)
 {
-	u32 v;
+	/* Release DDR ctrl reset */
-
+	__prci_consumer_reset("ddr_ctrl", true);
-	v = __prci_readl(pd, PRCI_DEVICESRESETREG_OFFSET);
-	v |= PRCI_DEVICESRESETREG_DDR_CTRL_RST_N_MASK;
-	__prci_writel(v, PRCI_DEVICESRESETREG_OFFSET, pd);
 
 	/* HACK to get the '1 full controller clock cycle'. */
 	asm volatile ("fence");
-	v = __prci_readl(pd, PRCI_DEVICESRESETREG_OFFSET);
+
-	v |= (PRCI_DEVICESRESETREG_DDR_AXI_RST_N_MASK |
+	/* Release DDR AXI reset */
-			PRCI_DEVICESRESETREG_DDR_AHB_RST_N_MASK |
+	__prci_consumer_reset("ddr_axi", true);
-			PRCI_DEVICESRESETREG_DDR_PHY_RST_N_MASK);
+
-	__prci_writel(v, PRCI_DEVICESRESETREG_OFFSET, pd);
+	/* Release DDR AHB reset */
+	__prci_consumer_reset("ddr_ahb", true);
+
+	/* Release DDR PHY reset */
+	__prci_consumer_reset("ddr_phy", true);
 
 	/* HACK to get the '1 full controller clock cycle'. */
 	asm volatile ("fence");
@@ -564,12 +605,8 @@ static void __prci_ddr_release_reset(struct __prci_data *pd)
  */
 static void __prci_ethernet_release_reset(struct __prci_data *pd)
 {
-	u32 v;
-
 	/* Release GEMGXL reset */
-	v = __prci_readl(pd, PRCI_DEVICESRESETREG_OFFSET);
+	__prci_consumer_reset("gemgxl_reset", true);
-	v |= PRCI_DEVICESRESETREG_GEMGXL_RST_N_MASK;
-	__prci_writel(v, PRCI_DEVICESRESETREG_OFFSET, pd);
 
 	/* Procmon => core clock */
 	__prci_writel(PRCI_PROCMONCFG_CORE_CLOCK_MASK, PRCI_PROCMONCFG_OFFSET,
@@ -754,6 +791,11 @@ static struct clk_ops sifive_fu540_prci_ops = {
 	.disable = sifive_fu540_prci_disable,
 };
 
+static int sifive_fu540_clk_bind(struct udevice *dev)
+{
+	return sifive_reset_bind(dev, PRCI_DEVICERESETCNT);
+}
+
 static const struct udevice_id sifive_fu540_prci_ids[] = {
 	{ .compatible = "sifive,fu540-c000-prci" },
 	{ }
@@ -766,4 +808,5 @@ U_BOOT_DRIVER(sifive_fu540_prci) = {
 	.probe = sifive_fu540_prci_probe,
 	.ops = &sifive_fu540_prci_ops,
 	.priv_auto_alloc_size = sizeof(struct __prci_data),
+	.bind = sifive_fu540_clk_bind,
 };

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),
+};