hwrng: histb - Move driver to drivers/char/hw_random/histb-rng.c

Move to drivers/char/hw_random since histb-(t)rng does not provide
cryptography pseudo rng.

histb-rng is pretty like hisi-rng, but after investigation, we confirm
there is no RNG_PHY_SEED register on histb-rng so a separate driver is
needed.

Still we rename relevant function names to match those in hisi-rng.

Link: https://lore.kernel.org/r/20230401164448.1393336-1-mmyangfl@gmail.com
Signed-off-by: David Yang <mmyangfl@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 185 insertions, 0 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index dbad0c57e54a..baefa2e0edbc 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -335,6 +335,17 @@ config HW_RANDOM_HISI
 
 	  If unsure, say Y.
 
+config HW_RANDOM_HISTB
+	tristate "Hisilicon STB Random Number Generator support"
+	depends on ARCH_HISI || COMPILE_TEST
+	default ARCH_HISI
+	help
+	  This driver provides kernel-side support for the Random Number
+	  Generator hardware found on Hisilicon Hi37xx SoC.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called histb-rng.
+
 config HW_RANDOM_ST
 	tristate "ST Microelectronics HW Random Number Generator support"
 	depends on HW_RANDOM && ARCH_STI
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 09bde4a0f971..32549a1186dc 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
 obj-$(CONFIG_HW_RANDOM_POWERNV) += powernv-rng.o
 obj-$(CONFIG_HW_RANDOM_HISI)	+= hisi-rng.o
+obj-$(CONFIG_HW_RANDOM_HISTB) += histb-rng.o
 obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
 obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
 obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
diff --git a/drivers/char/hw_random/histb-rng.c b/drivers/char/hw_random/histb-rng.c
new file mode 100644
index 000000000000..f652e1135e4b
--- /dev/null
+++ b/drivers/char/hw_random/histb-rng.c
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+/*
+ * Copyright (c) 2023 David Yang
+ */
+
+#include <linux/err.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#define RNG_CTRL		0x0
+#define  RNG_SOURCE			GENMASK(1, 0)
+#define  DROP_ENABLE			BIT(5)
+#define  POST_PROCESS_ENABLE		BIT(7)
+#define  POST_PROCESS_DEPTH		GENMASK(15, 8)
+#define RNG_NUMBER		0x4
+#define RNG_STAT		0x8
+#define  DATA_COUNT			GENMASK(2, 0)	/* max 4 */
+
+struct histb_rng_priv {
+	struct hwrng rng;
+	void __iomem *base;
+};
+
+/*
+ * Observed:
+ * depth = 1 -> ~1ms
+ * depth = 255 -> ~16ms
+ */
+static int histb_rng_wait(void __iomem *base)
+{
+	u32 val;
+
+	return readl_relaxed_poll_timeout(base + RNG_STAT, val,
+					  val & DATA_COUNT, 1000, 30 * 1000);
+}
+
+static void histb_rng_init(void __iomem *base, unsigned int depth)
+{
+	u32 val;
+
+	val = readl_relaxed(base + RNG_CTRL);
+
+	val &= ~RNG_SOURCE;
+	val |= 2;
+
+	val &= ~POST_PROCESS_DEPTH;
+	val |= min(depth, 0xffu) << 8;
+
+	val |= POST_PROCESS_ENABLE;
+	val |= DROP_ENABLE;
+
+	writel_relaxed(val, base + RNG_CTRL);
+}
+
+static int histb_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct histb_rng_priv *priv = container_of(rng, typeof(*priv), rng);
+	void __iomem *base = priv->base;
+
+	for (int i = 0; i < max; i += sizeof(u32)) {
+		if (!(readl_relaxed(base + RNG_STAT) & DATA_COUNT)) {
+			if (!wait)
+				return i;
+			if (histb_rng_wait(base)) {
+				pr_err("failed to generate random number, generated %d\n",
+				       i);
+				return i ? i : -ETIMEDOUT;
+			}
+		}
+		*(u32 *) (data + i) = readl_relaxed(base + RNG_NUMBER);
+	}
+
+	return max;
+}
+
+static unsigned int histb_rng_get_depth(void __iomem *base)
+{
+	return (readl_relaxed(base + RNG_CTRL) & POST_PROCESS_DEPTH) >> 8;
+}
+
+static ssize_t
+depth_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct histb_rng_priv *priv = dev_get_drvdata(dev);
+	void __iomem *base = priv->base;
+
+	return sprintf(buf, "%d\n", histb_rng_get_depth(base));
+}
+
+static ssize_t
+depth_store(struct device *dev, struct device_attribute *attr,
+	    const char *buf, size_t count)
+{
+	struct histb_rng_priv *priv = dev_get_drvdata(dev);
+	void __iomem *base = priv->base;
+	unsigned int depth;
+
+	if (kstrtouint(buf, 0, &depth))
+		return -ERANGE;
+
+	histb_rng_init(base, depth);
+	return count;
+}
+
+static DEVICE_ATTR_RW(depth);
+
+static struct attribute *histb_rng_attrs[] = {
+	&dev_attr_depth.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(histb_rng);
+
+static int histb_rng_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct histb_rng_priv *priv;
+	void __iomem *base;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	histb_rng_init(base, 144);
+	if (histb_rng_wait(base)) {
+		dev_err(dev, "cannot bring up device\n");
+		return -ENODEV;
+	}
+
+	priv->base = base;
+	priv->rng.name = pdev->name;
+	priv->rng.read = histb_rng_read;
+	ret = devm_hwrng_register(dev, &priv->rng);
+	if (ret) {
+		dev_err(dev, "failed to register hwrng: %d\n", ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, priv);
+	dev_set_drvdata(dev, priv);
+	return 0;
+}
+
+static const struct of_device_id histb_rng_of_match[] = {
+	{ .compatible = "hisilicon,histb-rng", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, histb_rng_of_match);
+
+static struct platform_driver histb_rng_driver = {
+	.probe = histb_rng_probe,
+	.driver = {
+		.name = "histb-rng",
+		.of_match_table = histb_rng_of_match,
+		.dev_groups = histb_rng_groups,
+	},
+};
+
+module_platform_driver(histb_rng_driver);
+
+MODULE_DESCRIPTION("Hisilicon STB random number generator driver");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_AUTHOR("David Yang <mmyangfl@gmail.com>");