drivers/rng: add Amlogic hardware RNG driver

Add support for the hardware random number generator of Amlogic SOCs.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Sughosh Ganu <sughosh.ganu@linaro.org>

drivers/rng/Kconfig

@@ -8,6 +8,14 @@ config DM_RNG
 
 if DM_RNG
 
+config RNG_MESON
+	bool "Amlogic Meson Random Number Generator support"
+	depends on ARCH_MESON
+	default y
+	help
+	  Enable support for hardware random number generator
+	  of Amlogic Meson SoCs.
+
 config RNG_SANDBOX
 	bool "Sandbox random number generator"
 	depends on SANDBOX

drivers/rng/Makefile

@@ -4,5 +4,6 @@
 #
 
 obj-$(CONFIG_DM_RNG) += rng-uclass.o
+obj-$(CONFIG_RNG_MESON) += meson-rng.o
 obj-$(CONFIG_RNG_SANDBOX) += sandbox_rng.o
 obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o

drivers/rng/meson-rng.c

@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2020, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ *
+ * Driver for Amlogic hardware random number generator
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <dm.h>
+#include <rng.h>
+#include <asm/io.h>
+
+struct meson_rng_platdata {
+	fdt_addr_t base;
+	struct clk clk;
+};
+
+/**
+ * meson_rng_read() - fill buffer with random bytes
+ *
+ * @buffer:	buffer to receive data
+ * @size:	size of buffer
+ *
+ * Return:	0
+ */
+static int meson_rng_read(struct udevice *dev, void *data, size_t len)
+{
+	struct meson_rng_platdata *pdata = dev_get_platdata(dev);
+	char *buffer = (char *)data;
+
+	while (len) {
+		u32 rand = readl(pdata->base);
+		size_t step;
+
+		if (len >= 4)
+			step = 4;
+		else
+			step = len;
+		memcpy(buffer, &rand, step);
+		buffer += step;
+		len -= step;
+	}
+	return 0;
+}
+
+/**
+ * meson_rng_probe() - probe rng device
+ *
+ * @dev:	device
+ * Return:	0 if ok
+ */
+static int meson_rng_probe(struct udevice *dev)
+{
+	struct meson_rng_platdata *pdata = dev_get_platdata(dev);
+	int err;
+
+	err = clk_enable(&pdata->clk);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+/**
+ * meson_rng_remove() - deinitialize rng device
+ *
+ * @dev:	device
+ * Return:	0 if ok
+ */
+static int meson_rng_remove(struct udevice *dev)
+{
+	struct meson_rng_platdata *pdata = dev_get_platdata(dev);
+
+	return clk_disable(&pdata->clk);
+}
+
+/**
+ * meson_rng_ofdata_to_platdata() - transfer device tree data to plaform data
+ *
+ * @dev:	device
+ * Return:	0 if ok
+ */
+static int meson_rng_ofdata_to_platdata(struct udevice *dev)
+{
+	struct meson_rng_platdata *pdata = dev_get_platdata(dev);
+	int err;
+
+	pdata->base = dev_read_addr(dev);
+	if (!pdata->base)
+		return -ENODEV;
+
+	err = clk_get_by_name(dev, "core", &pdata->clk);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static const struct dm_rng_ops meson_rng_ops = {
+	.read = meson_rng_read,
+};
+
+static const struct udevice_id meson_rng_match[] = {
+	{
+		.compatible = "amlogic,meson-rng",
+	},
+	{},
+};
+
+U_BOOT_DRIVER(meson_rng) = {
+	.name = "meson-rng",
+	.id = UCLASS_RNG,
+	.of_match = meson_rng_match,
+	.ops = &meson_rng_ops,
+	.probe = meson_rng_probe,
+	.remove = meson_rng_remove,
+	.platdata_auto_alloc_size = sizeof(struct meson_rng_platdata),
+	.ofdata_to_platdata = meson_rng_ofdata_to_platdata,
+};