[PATCH] crypto: sun4i-ss: support the Security System PRNG

[Corentin Labbe]

From: LABBE Corentin <clabbe.montjoie at gmail.com>

The Security System have a PRNG.
This patch add support for it as an hwrng.

Signed-off-by: Corentin Labbe <clabbe.montjoie at gmail.com>
---
 drivers/crypto/Kconfig                   |  8 ++++
 drivers/crypto/sunxi-ss/Makefile         |  1 +
 drivers/crypto/sunxi-ss/sun4i-ss-core.c  | 14 +++++++
 drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c | 70 ++++++++++++++++++++++++++++++++
 drivers/crypto/sunxi-ss/sun4i-ss.h       |  8 ++++
 5 files changed, 101 insertions(+)
 create mode 100644 drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c

diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
index 4d2b81f..38f7aca 100644
--- a/drivers/crypto/Kconfig
+++ b/drivers/crypto/Kconfig
@@ -538,6 +538,14 @@ config CRYPTO_DEV_SUN4I_SS
 	  To compile this driver as a module, choose M here: the module
 	  will be called sun4i-ss.
 
+config CRYPTO_DEV_SUN4I_SS_PRNG
+	bool "Support for Allwinner Security System PRNG"
+	depends on CRYPTO_DEV_SUN4I_SS
+	select HW_RANDOM
+	help
+	  This driver provides kernel-side support for the Pseudo-Random
+	  Number Generator found in the Security System.
+
 config CRYPTO_DEV_ROCKCHIP
 	tristate "Rockchip's Cryptographic Engine driver"
 	depends on OF && ARCH_ROCKCHIP
diff --git a/drivers/crypto/sunxi-ss/Makefile b/drivers/crypto/sunxi-ss/Makefile
index 8f4c7a2..ca049ee 100644
--- a/drivers/crypto/sunxi-ss/Makefile
+++ b/drivers/crypto/sunxi-ss/Makefile
@@ -1,2 +1,3 @@
 obj-$(CONFIG_CRYPTO_DEV_SUN4I_SS) += sun4i-ss.o
 sun4i-ss-y += sun4i-ss-core.o sun4i-ss-hash.o sun4i-ss-cipher.o
+sun4i-ss-$(CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG) += sun4i-ss-hwrng.o
diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-core.c b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
index 3ac6c6c..fa739de 100644
--- a/drivers/crypto/sunxi-ss/sun4i-ss-core.c
+++ b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
@@ -359,6 +359,16 @@ static int sun4i_ss_probe(struct platform_device *pdev)
 		}
 	}
 	platform_set_drvdata(pdev, ss);
+
+#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
+	/* Voluntarily made the PRNG optional */
+	err = sun4i_ss_hwrng_register(&ss->hwrng);
+	if (!err)
+		dev_info(ss->dev, "sun4i-ss PRNG loaded");
+	else
+		dev_err(ss->dev, "sun4i-ss PRNG failed");
+#endif
+
 	return 0;
 error_alg:
 	i--;
@@ -386,6 +396,10 @@ static int sun4i_ss_remove(struct platform_device *pdev)
 	int i;
 	struct sun4i_ss_ctx *ss = platform_get_drvdata(pdev);
 
+#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
+	sun4i_ss_hwrng_remove(&ss->hwrng);
+#endif
+
 	for (i = 0; i < ARRAY_SIZE(ss_algs); i++) {
 		switch (ss_algs[i].type) {
 		case CRYPTO_ALG_TYPE_ABLKCIPHER:
diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
new file mode 100644
index 0000000..95fadb7
--- /dev/null
+++ b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
@@ -0,0 +1,70 @@
+#include "sun4i-ss.h"
+
+static int sun4i_ss_hwrng_init(struct hwrng *hwrng)
+{
+	struct sun4i_ss_ctx *ss;
+
+	ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
+	get_random_bytes(ss->seed, SS_SEED_LEN);
+
+	return 0;
+}
+
+static int sun4i_ss_hwrng_read(struct hwrng *hwrng, void *buf,
+			       size_t max, bool wait)
+{
+	int i;
+	u32 v;
+	u32 *data = buf;
+	const u32 mode = SS_OP_PRNG | SS_PRNG_CONTINUE | SS_ENABLED;
+	size_t len;
+	struct sun4i_ss_ctx *ss;
+
+	ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
+	len = min_t(size_t, SS_DATA_LEN, max);
+
+	spin_lock_bh(&ss->slock);
+
+	writel(mode, ss->base + SS_CTL);
+
+	/* write the seed */
+	for (i = 0; i < SS_SEED_LEN / 4; i++)
+		writel(ss->seed[i], ss->base + SS_KEY0 + i * 4);
+	writel(mode | SS_PRNG_START, ss->base + SS_CTL);
+
+	/* Read the random data */
+	readsl(ss->base + SS_TXFIFO, data, len / 4);
+
+	if (len % 4 > 0) {
+		v = readl(ss->base + SS_TXFIFO);
+		memcpy(data + len / 4, &v, len % 4);
+	}
+
+	/* Update the seed */
+	for (i = 0; i < SS_SEED_LEN / 4; i++) {
+		v = readl(ss->base + SS_KEY0 + i * 4);
+		ss->seed[i] = v;
+	}
+
+	writel(0, ss->base + SS_CTL);
+	spin_unlock_bh(&ss->slock);
+	return len;
+}
+
+int sun4i_ss_hwrng_register(struct hwrng *hwrng)
+{
+	hwrng->name = "sun4i Security System PRNG";
+	hwrng->init = sun4i_ss_hwrng_init;
+	hwrng->read = sun4i_ss_hwrng_read;
+	hwrng->quality = 1000;
+
+	/* Cannot use devm_hwrng_register() since we need to hwrng_unregister
+	 * before stopping clocks/regulator
+	 */
+	return hwrng_register(hwrng);
+}
+
+void sun4i_ss_hwrng_remove(struct hwrng *hwrng)
+{
+	hwrng_unregister(hwrng);
+}
diff --git a/drivers/crypto/sunxi-ss/sun4i-ss.h b/drivers/crypto/sunxi-ss/sun4i-ss.h
index f04c0f8..1297510 100644
--- a/drivers/crypto/sunxi-ss/sun4i-ss.h
+++ b/drivers/crypto/sunxi-ss/sun4i-ss.h
@@ -23,6 +23,7 @@
 #include <linux/scatterlist.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
+#include <linux/hw_random.h>
 #include <crypto/md5.h>
 #include <crypto/sha.h>
 #include <crypto/hash.h>
@@ -125,6 +126,9 @@
 #define SS_RXFIFO_EMP_INT_ENABLE	(1 << 2)
 #define SS_TXFIFO_AVA_INT_ENABLE	(1 << 0)
 
+#define SS_SEED_LEN (192 / 8)
+#define SS_DATA_LEN (160 / 8)
+
 struct sun4i_ss_ctx {
 	void __iomem *base;
 	int irq;
@@ -134,6 +138,8 @@ struct sun4i_ss_ctx {
 	struct device *dev;
 	struct resource *res;
 	spinlock_t slock; /* control the use of the device */
+	struct hwrng hwrng;
+	u32 seed[SS_SEED_LEN / 4];
 };
 
 struct sun4i_ss_alg_template {
@@ -199,3 +205,5 @@ int sun4i_ss_des_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
 			unsigned int keylen);
 int sun4i_ss_des3_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
 			 unsigned int keylen);
+int sun4i_ss_hwrng_register(struct hwrng *hwrng);
+void sun4i_ss_hwrng_remove(struct hwrng *hwrng);
-- 
2.7.3