rng: Add iProc RNG200 driver

Add support for random number generator RNG200.
This is for example found on RPi4.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
[mb: adapt to new struct driver memebers]
Signed-off-by: Matthias Brugger <mbrugger@suse.com>

drivers/rng/Kconfig

@@ -46,4 +46,10 @@ config RNG_ROCKCHIP
 	  Enable random number generator for rockchip.This driver is
 	  support rng module of crypto v1 and crypto v2.
 
+config RNG_IPROC200
+	bool "Broadcom iProc RNG200 random number generator"
+	depends on DM_RNG
+	default n
+	help
+	  Enable random number generator for RPI4.
 endif

drivers/rng/Makefile

@@ -9,3 +9,4 @@ obj-$(CONFIG_RNG_SANDBOX) += sandbox_rng.o
 obj-$(CONFIG_RNG_MSM) += msm_rng.o
 obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o
 obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o
+obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o

drivers/rng/iproc_rng200.c

@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2020, Matthias Brugger <mbrugger@suse.com>
+ *
+ * Driver for Raspberry Pi hardware random number generator
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <linux/delay.h>
+#include <rng.h>
+#include <asm/io.h>
+
+#define usleep_range(a, b) udelay((b))
+
+#define RNG_CTRL_OFFSET					0x00
+#define RNG_CTRL_RNG_RBGEN_MASK				0x00001FFF
+#define RNG_CTRL_RNG_RBGEN_ENABLE			0x00000001
+#define RNG_CTRL_RNG_RBGEN_DISABLE			0x00000000
+
+#define RNG_SOFT_RESET_OFFSET				0x04
+#define RNG_SOFT_RESET					0x00000001
+
+#define RBG_SOFT_RESET_OFFSET				0x08
+#define RBG_SOFT_RESET					0x00000001
+
+#define RNG_INT_STATUS_OFFSET				0x18
+#define RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK	0x80000000
+#define RNG_INT_STATUS_NIST_FAIL_IRQ_MASK		0x00000020
+
+#define RNG_FIFO_DATA_OFFSET				0x20
+
+#define RNG_FIFO_COUNT_OFFSET				0x24
+#define RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK		0x000000FF
+
+struct iproc_rng200_platdata {
+	fdt_addr_t base;
+};
+
+static void iproc_rng200_enable(struct iproc_rng200_platdata *pdata, bool enable)
+{
+	fdt_addr_t rng_base = pdata->base;
+	u32 val;
+
+	val = readl(rng_base + RNG_CTRL_OFFSET);
+	val &= ~RNG_CTRL_RNG_RBGEN_MASK;
+	if (enable)
+		val |= RNG_CTRL_RNG_RBGEN_ENABLE;
+	else
+		val &= ~RNG_CTRL_RNG_RBGEN_ENABLE;
+
+	writel(val, rng_base + RNG_CTRL_OFFSET);
+
+}
+
+static void iproc_rng200_restart(struct iproc_rng200_platdata *pdata)
+{
+	fdt_addr_t rng_base = pdata->base;
+	u32 val;
+
+	iproc_rng200_enable(pdata, false);
+
+	/* Clear all interrupt status */
+	writel(0xFFFFFFFFUL, rng_base + RNG_INT_STATUS_OFFSET);
+
+	/* Reset RNG and RBG */
+	val = readl(rng_base + RBG_SOFT_RESET_OFFSET);
+	val |= RBG_SOFT_RESET;
+	writel(val, rng_base + RBG_SOFT_RESET_OFFSET);
+
+	val = readl(rng_base + RNG_SOFT_RESET_OFFSET);
+	val |= RNG_SOFT_RESET;
+	writel(val, rng_base + RNG_SOFT_RESET_OFFSET);
+
+	val = readl(rng_base + RNG_SOFT_RESET_OFFSET);
+	val &= ~RNG_SOFT_RESET;
+	writel(val, rng_base + RNG_SOFT_RESET_OFFSET);
+
+	val = readl(rng_base + RBG_SOFT_RESET_OFFSET);
+	val &= ~RBG_SOFT_RESET;
+	writel(val, rng_base + RBG_SOFT_RESET_OFFSET);
+
+	iproc_rng200_enable(pdata, true);
+}
+
+static int iproc_rng200_read(struct udevice *dev, void *data, size_t len)
+{
+	struct iproc_rng200_platdata *priv = dev_get_plat(dev);
+	char *buf = (char *)data;
+	u32 num_remaining = len;
+	u32 status;
+
+	#define MAX_RESETS_PER_READ	1
+	u32 num_resets = 0;
+
+	while (num_remaining > 0) {
+
+		/* Is RNG sane? If not, reset it. */
+		status = readl(priv->base + RNG_INT_STATUS_OFFSET);
+		if ((status & (RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK |
+			RNG_INT_STATUS_NIST_FAIL_IRQ_MASK)) != 0) {
+
+			if (num_resets >= MAX_RESETS_PER_READ)
+				return len - num_remaining;
+
+			iproc_rng200_restart(priv);
+			num_resets++;
+		}
+
+		/* Are there any random numbers available? */
+		if ((readl(priv->base + RNG_FIFO_COUNT_OFFSET) &
+				RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK) > 0) {
+
+			if (num_remaining >= sizeof(u32)) {
+				/* Buffer has room to store entire word */
+				*(u32 *)buf = readl(priv->base +
+							RNG_FIFO_DATA_OFFSET);
+				buf += sizeof(u32);
+				num_remaining -= sizeof(u32);
+			} else {
+				/* Buffer can only store partial word */
+				u32 rnd_number = readl(priv->base +
+							RNG_FIFO_DATA_OFFSET);
+				memcpy(buf, &rnd_number, num_remaining);
+				buf += num_remaining;
+				num_remaining = 0;
+			}
+
+		} else {
+			/* Can wait, give others chance to run */
+			usleep_range(min(num_remaining * 10, 500U), 500);
+		}
+	}
+
+	return 0;
+}
+
+static int iproc_rng200_probe(struct udevice *dev)
+{
+	struct iproc_rng200_platdata *priv = dev_get_plat(dev);
+
+	iproc_rng200_enable(priv, true);
+
+	return 0;
+}
+
+static int iproc_rng200_remove(struct udevice *dev)
+{
+	struct iproc_rng200_platdata *priv = dev_get_plat(dev);
+
+	iproc_rng200_enable(priv, false);
+
+	return 0;
+}
+
+static int iproc_rng200_ofdata_to_platdata(struct udevice *dev)
+{
+	struct iproc_rng200_platdata *pdata = dev_get_plat(dev);
+
+	pdata->base = dev_read_addr(dev);
+	if (!pdata->base)
+		return -ENODEV;
+
+	return 0;
+}
+
+static const struct dm_rng_ops iproc_rng200_ops = {
+	.read = iproc_rng200_read,
+};
+
+static const struct udevice_id iproc_rng200_rng_match[] = {
+	{ .compatible = "brcm,bcm2711-rng200", },
+	{ .compatible = "brcm,iproc-rng200", },
+	{},
+};
+
+U_BOOT_DRIVER(iproc_rng200_rng) = {
+	.name = "iproc_rng200-rng",
+	.id = UCLASS_RNG,
+	.of_match = iproc_rng200_rng_match,
+	.ops = &iproc_rng200_ops,
+	.probe = iproc_rng200_probe,
+	.remove = iproc_rng200_remove,
+	.plat_auto = sizeof(struct iproc_rng200_platdata),
+	.of_to_plat = iproc_rng200_ofdata_to_platdata,
+};