[PATCH 3/6] crypto: jz4780-rng: Add Ingenic JZ4780 hardware PRNG driver

[PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>]

JZ4780 SoC pseudo random number generator driver using crypto framework.

Adding a delay before reading RNG data and disabling RNG after reading
data was suggested by Jeffery Walton.

Tested-by: Mathieu Malaterre <malat@debian.org>
Suggested-by: Jeffrey Walton <noloader@gmail.com>
Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
---
 drivers/crypto/Kconfig      |  19 +++++
 drivers/crypto/Makefile     |   1 +
 drivers/crypto/jz4780-rng.c | 173 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 193 insertions(+)
 create mode 100644 drivers/crypto/jz4780-rng.c

diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
index 8fa7e72..8263622 100644
--- a/drivers/crypto/Kconfig
+++ b/drivers/crypto/Kconfig
@@ -614,6 +614,25 @@ config CRYPTO_DEV_IMGTEC_HASH
 	  hardware hash accelerator. Supporting MD5/SHA1/SHA224/SHA256
 	  hashing algorithms.
 
+config CRYPTO_DEV_JZ4780_RNG
+	tristate "JZ4780 HW pseudo random number generator support"
+	depends on MACH_JZ4780 || COMPILE_TEST
+	depends on HAS_IOMEM
+	select CRYPTO_RNG
+	select REGMAP
+	select SYSCON
+	select MFD_SYSCON
+	---help---
+	  This driver provides kernel-side support through the
+	  cryptographic API for the pseudo random number generator
+	  hardware found in ingenic JZ4780 and X1000 SoC. MIPS
+	  Creator CI20 uses JZ4780 SoC.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called jz4780-rng.
+
+	  If unsure, say Y.
+
 config CRYPTO_DEV_SUN4I_SS
 	tristate "Support for Allwinner Security System cryptographic accelerator"
 	depends on ARCH_SUNXI && !64BIT
diff --git a/drivers/crypto/Makefile b/drivers/crypto/Makefile
index b12eb3c..3a3d970 100644
--- a/drivers/crypto/Makefile
+++ b/drivers/crypto/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_CRYPTO_DEV_GEODE) += geode-aes.o
 obj-$(CONFIG_CRYPTO_DEV_HIFN_795X) += hifn_795x.o
 obj-$(CONFIG_CRYPTO_DEV_IMGTEC_HASH) += img-hash.o
 obj-$(CONFIG_CRYPTO_DEV_IXP4XX) += ixp4xx_crypto.o
+obj-$(CONFIG_CRYPTO_DEV_JZ4780_RNG) += jz4780-rng.o
 obj-$(CONFIG_CRYPTO_DEV_MV_CESA) += mv_cesa.o
 obj-$(CONFIG_CRYPTO_DEV_MARVELL_CESA) += marvell/
 obj-$(CONFIG_CRYPTO_DEV_MEDIATEK) += mediatek/
diff --git a/drivers/crypto/jz4780-rng.c b/drivers/crypto/jz4780-rng.c
new file mode 100644
index 0000000..a03f2a0
--- /dev/null
+++ b/drivers/crypto/jz4780-rng.c
@@ -0,0 +1,173 @@
+/*
+ * jz4780-rng.c - Random Number Generator driver for the jz4780
+ *
+ * Copyright (c) 2017 PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/crypto.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#include <crypto/internal/rng.h>
+
+#define REG_RNG_CTRL	0xD8
+#define REG_RNG_DATA	0xDC
+
+/* Context for crypto */
+struct jz4780_rng_ctx {
+	struct jz4780_rng *rng;
+};
+
+/* Device associated memory */
+struct jz4780_rng {
+	struct device *dev;
+	struct regmap *regmap;
+};
+
+static struct jz4780_rng *jz4780_rng;
+
+static int jz4780_rng_readl(struct jz4780_rng *rng, u32 offset)
+{
+	u32 val = 0;
+	int ret;
+
+	ret = regmap_read(rng->regmap, offset, &val);
+	if (!ret)
+		return val;
+
+	return ret;
+}
+
+static int jz4780_rng_writel(struct jz4780_rng *rng, u32 val, u32 offset)
+{
+	return regmap_write(rng->regmap, offset, val);
+}
+
+static int jz4780_rng_generate(struct crypto_rng *tfm,
+			       const u8 *src, unsigned int slen,
+			       u8 *dst, unsigned int dlen)
+{
+	struct jz4780_rng_ctx *ctx = crypto_rng_ctx(tfm);
+	struct jz4780_rng *rng = ctx->rng;
+	u32 data;
+
+	/*
+	 * JZ4780 Programmers manual says the RNG should not run continuously
+	 * for more than 1s. So enable RNG, read data and disable it.
+	 * NOTE: No issue was observed with MIPS creator CI20 board even when
+	 * RNG ran continuously for longer periods. This is just a precaution.
+	 *
+	 * A delay is required so that the current RNG data is not bit shifted
+	 * version of previous RNG data which could happen if random data is
+	 * read continuously from this device.
+	 */
+	jz4780_rng_writel(rng, 1, REG_RNG_CTRL);
+	do {
+		data = jz4780_rng_readl(rng, REG_RNG_DATA);
+		memcpy((void *)dst, (void *)&data, 4);
+		dlen -= 4;
+		dst += 4;
+		udelay(20);
+	} while (dlen >= 4);
+
+	if (dlen > 0) {
+		data = jz4780_rng_readl(rng, REG_RNG_DATA);
+		memcpy((void *)dst, (void *)&data, dlen);
+	}
+	jz4780_rng_writel(rng, 0, REG_RNG_CTRL);
+
+	return 0;
+}
+
+static int jz4780_rng_kcapi_init(struct crypto_tfm *tfm)
+{
+	struct jz4780_rng_ctx *ctx = crypto_tfm_ctx(tfm);
+
+	ctx->rng = jz4780_rng;
+
+	return 0;
+}
+
+static struct rng_alg jz4780_rng_alg = {
+	.generate		= jz4780_rng_generate,
+	.base			= {
+		.cra_name		= "stdrng",
+		.cra_driver_name	= "jz4780_rng",
+		.cra_priority		= 100,
+		.cra_ctxsize		= sizeof(struct jz4780_rng_ctx),
+		.cra_module		= THIS_MODULE,
+		.cra_init		= jz4780_rng_kcapi_init,
+	}
+};
+
+static int jz4780_rng_probe(struct platform_device *pdev)
+{
+	struct jz4780_rng *rng;
+	struct resource *res;
+	int ret;
+
+	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
+	if (!rng)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	rng->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(rng->regmap))
+		return PTR_ERR(rng->regmap);
+
+	jz4780_rng = rng;
+
+	ret = crypto_register_rng(&jz4780_rng_alg);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"Couldn't register rng crypto alg: %d\n", ret);
+		jz4780_rng = NULL;
+	}
+
+	return ret;
+}
+
+static int jz4780_rng_remove(struct platform_device *pdev)
+{
+	crypto_unregister_rng(&jz4780_rng_alg);
+
+	jz4780_rng = NULL;
+
+	return 0;
+}
+
+static const struct of_device_id jz4780_rng_dt_match[] = {
+	{
+		.compatible = "ingenic,jz4780-rng",
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, jz4780_rng_dt_match);
+
+static struct platform_driver jz4780_rng_driver = {
+	.driver		= {
+		.name	= "jz4780-rng",
+		.of_match_table = jz4780_rng_dt_match,
+	},
+	.probe		= jz4780_rng_probe,
+	.remove		= jz4780_rng_remove,
+};
+
+module_platform_driver(jz4780_rng_driver);
+
+MODULE_DESCRIPTION("Ingenic JZ4780 H/W Pseudo Random Number Generator driver");
+MODULE_AUTHOR("PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>");
+MODULE_LICENSE("GPL");
-- 
2.10.0