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@@ -0,0 +1,389 @@
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+/*
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+ * exynos-rng.c - Random Number Generator driver for the Exynos
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+ *
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+ * Copyright (c) 2017 Krzysztof Kozlowski <krzk@kernel.org>
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+ *
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+ * Loosely based on old driver from drivers/char/hw_random/exynos-rng.c:
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+ * Copyright (C) 2012 Samsung Electronics
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+ * Jonghwa Lee <jonghwa3.lee@samsung.com>
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation;
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ */
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+
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+#include <linux/clk.h>
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+#include <linux/crypto.h>
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+#include <linux/err.h>
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+#include <linux/io.h>
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+#include <linux/module.h>
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+#include <linux/platform_device.h>
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+
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+#include <crypto/internal/rng.h>
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+
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+#define EXYNOS_RNG_CONTROL 0x0
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+#define EXYNOS_RNG_STATUS 0x10
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+#define EXYNOS_RNG_SEED_BASE 0x140
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+#define EXYNOS_RNG_SEED(n) (EXYNOS_RNG_SEED_BASE + (n * 0x4))
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+#define EXYNOS_RNG_OUT_BASE 0x160
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+#define EXYNOS_RNG_OUT(n) (EXYNOS_RNG_OUT_BASE + (n * 0x4))
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+
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+/* EXYNOS_RNG_CONTROL bit fields */
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+#define EXYNOS_RNG_CONTROL_START 0x18
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+/* EXYNOS_RNG_STATUS bit fields */
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+#define EXYNOS_RNG_STATUS_SEED_SETTING_DONE BIT(1)
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+#define EXYNOS_RNG_STATUS_RNG_DONE BIT(5)
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+
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+/* Five seed and output registers, each 4 bytes */
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+#define EXYNOS_RNG_SEED_REGS 5
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+#define EXYNOS_RNG_SEED_SIZE (EXYNOS_RNG_SEED_REGS * 4)
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+
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+/*
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+ * Driver re-seeds itself with generated random numbers to increase
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+ * the randomness.
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+ *
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+ * Time for next re-seed in ms.
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+ */
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+#define EXYNOS_RNG_RESEED_TIME 100
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+/*
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+ * In polling mode, do not wait infinitely for the engine to finish the work.
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+ */
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+#define EXYNOS_RNG_WAIT_RETRIES 100
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+
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+/* Context for crypto */
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+struct exynos_rng_ctx {
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+ struct exynos_rng_dev *rng;
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+};
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+
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+/* Device associated memory */
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+struct exynos_rng_dev {
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+ struct device *dev;
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+ void __iomem *mem;
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+ struct clk *clk;
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+ /* Generated numbers stored for seeding during resume */
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+ u8 seed_save[EXYNOS_RNG_SEED_SIZE];
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+ unsigned int seed_save_len;
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+ /* Time of last seeding in jiffies */
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+ unsigned long last_seeding;
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+};
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+
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+static struct exynos_rng_dev *exynos_rng_dev;
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+
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+static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset)
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+{
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+ return readl_relaxed(rng->mem + offset);
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+}
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+
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+static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset)
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+{
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+ writel_relaxed(val, rng->mem + offset);
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+}
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+
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+static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
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+ const u8 *seed, unsigned int slen)
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+{
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+ u32 val;
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+ int i;
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+
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+ /* Round seed length because loop iterates over full register size */
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+ slen = ALIGN_DOWN(slen, 4);
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+
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+ if (slen < EXYNOS_RNG_SEED_SIZE)
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+ return -EINVAL;
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+
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+ for (i = 0; i < slen ; i += 4) {
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+ unsigned int seed_reg = (i / 4) % EXYNOS_RNG_SEED_REGS;
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+
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+ val = seed[i] << 24;
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+ val |= seed[i + 1] << 16;
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+ val |= seed[i + 2] << 8;
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+ val |= seed[i + 3] << 0;
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+
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+ exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(seed_reg));
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+ }
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+
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+ val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
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+ if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
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+ dev_warn(rng->dev, "Seed setting not finished\n");
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+ return -EIO;
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+ }
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+
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+ rng->last_seeding = jiffies;
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+
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+ return 0;
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+}
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+
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+/*
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+ * Read from output registers and put the data under 'dst' array,
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+ * up to dlen bytes.
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+ *
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+ * Returns number of bytes actually stored in 'dst' (dlen
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+ * or EXYNOS_RNG_SEED_SIZE).
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+ */
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+static unsigned int exynos_rng_copy_random(struct exynos_rng_dev *rng,
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+ u8 *dst, unsigned int dlen)
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+{
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+ unsigned int cnt = 0;
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+ int i, j;
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+ u32 val;
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+
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+ for (j = 0; j < EXYNOS_RNG_SEED_REGS; j++) {
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+ val = exynos_rng_readl(rng, EXYNOS_RNG_OUT(j));
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+
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+ for (i = 0; i < 4; i++) {
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+ dst[cnt] = val & 0xff;
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+ val >>= 8;
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+ if (++cnt >= dlen)
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+ return cnt;
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+ }
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+ }
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+
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+ return cnt;
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+}
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+
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+/*
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+ * Start the engine and poll for finish. Then read from output registers
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+ * filling the 'dst' buffer up to 'dlen' bytes or up to size of generated
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+ * random data (EXYNOS_RNG_SEED_SIZE).
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+ *
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+ * On success: return 0 and store number of read bytes under 'read' address.
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+ * On error: return -ERRNO.
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+ */
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+static int exynos_rng_get_random(struct exynos_rng_dev *rng,
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+ u8 *dst, unsigned int dlen,
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+ unsigned int *read)
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+{
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+ int retry = EXYNOS_RNG_WAIT_RETRIES;
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+
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+ exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
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+ EXYNOS_RNG_CONTROL);
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+
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+ while (!(exynos_rng_readl(rng,
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+ EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
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+ cpu_relax();
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+
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+ if (!retry)
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+ return -ETIMEDOUT;
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+
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+ /* Clear status bit */
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+ exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE,
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+ EXYNOS_RNG_STATUS);
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+ *read = exynos_rng_copy_random(rng, dst, dlen);
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+
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+ return 0;
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+}
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+
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+/* Re-seed itself from time to time */
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+static void exynos_rng_reseed(struct exynos_rng_dev *rng)
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+{
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+ unsigned long next_seeding = rng->last_seeding + \
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+ msecs_to_jiffies(EXYNOS_RNG_RESEED_TIME);
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+ unsigned long now = jiffies;
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+ unsigned int read = 0;
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+ u8 seed[EXYNOS_RNG_SEED_SIZE];
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+
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+ if (time_before(now, next_seeding))
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+ return;
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+
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+ if (exynos_rng_get_random(rng, seed, sizeof(seed), &read))
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+ return;
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+
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+ exynos_rng_set_seed(rng, seed, read);
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+}
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+
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+static int exynos_rng_generate(struct crypto_rng *tfm,
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+ const u8 *src, unsigned int slen,
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+ u8 *dst, unsigned int dlen)
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+{
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+ struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
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+ struct exynos_rng_dev *rng = ctx->rng;
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+ unsigned int read = 0;
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+ int ret;
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+
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+ ret = clk_prepare_enable(rng->clk);
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+ if (ret)
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+ return ret;
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+
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+ do {
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+ ret = exynos_rng_get_random(rng, dst, dlen, &read);
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+ if (ret)
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+ break;
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+
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+ dlen -= read;
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+ dst += read;
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+
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+ exynos_rng_reseed(rng);
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+ } while (dlen > 0);
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+
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+ clk_disable_unprepare(rng->clk);
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+
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+ return ret;
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+}
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+
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+static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed,
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+ unsigned int slen)
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+{
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+ struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
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+ struct exynos_rng_dev *rng = ctx->rng;
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+ int ret;
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+
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+ ret = clk_prepare_enable(rng->clk);
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+ if (ret)
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+ return ret;
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+
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+ ret = exynos_rng_set_seed(ctx->rng, seed, slen);
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+
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+ clk_disable_unprepare(rng->clk);
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+
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+ return ret;
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+}
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+
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+static int exynos_rng_kcapi_init(struct crypto_tfm *tfm)
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+{
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+ struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm);
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+
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+ ctx->rng = exynos_rng_dev;
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+
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+ return 0;
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+}
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+
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+static struct rng_alg exynos_rng_alg = {
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+ .generate = exynos_rng_generate,
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+ .seed = exynos_rng_seed,
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+ .seedsize = EXYNOS_RNG_SEED_SIZE,
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+ .base = {
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+ .cra_name = "stdrng",
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+ .cra_driver_name = "exynos_rng",
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+ .cra_priority = 100,
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+ .cra_ctxsize = sizeof(struct exynos_rng_ctx),
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+ .cra_module = THIS_MODULE,
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+ .cra_init = exynos_rng_kcapi_init,
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+ }
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+};
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+
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+static int exynos_rng_probe(struct platform_device *pdev)
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+{
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+ struct exynos_rng_dev *rng;
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+ struct resource *res;
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+ int ret;
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+
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+ if (exynos_rng_dev)
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+ return -EEXIST;
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+
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+ rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
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+ if (!rng)
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+ return -ENOMEM;
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+
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+ rng->dev = &pdev->dev;
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+ rng->clk = devm_clk_get(&pdev->dev, "secss");
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+ if (IS_ERR(rng->clk)) {
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+ dev_err(&pdev->dev, "Couldn't get clock.\n");
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+ return PTR_ERR(rng->clk);
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+ }
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+
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+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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+ rng->mem = devm_ioremap_resource(&pdev->dev, res);
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+ if (IS_ERR(rng->mem))
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+ return PTR_ERR(rng->mem);
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+
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+ platform_set_drvdata(pdev, rng);
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+
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+ exynos_rng_dev = rng;
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+
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+ ret = crypto_register_rng(&exynos_rng_alg);
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+ if (ret) {
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+ dev_err(&pdev->dev,
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+ "Couldn't register rng crypto alg: %d\n", ret);
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+ exynos_rng_dev = NULL;
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+ }
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+
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+ return ret;
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+}
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+
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+static int exynos_rng_remove(struct platform_device *pdev)
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+{
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+ crypto_unregister_rng(&exynos_rng_alg);
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+
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+ exynos_rng_dev = NULL;
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+
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+ return 0;
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+}
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+
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+static int __maybe_unused exynos_rng_suspend(struct device *dev)
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+{
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+ struct platform_device *pdev = to_platform_device(dev);
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+ struct exynos_rng_dev *rng = platform_get_drvdata(pdev);
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+ int ret;
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+
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+ /* If we were never seeded then after resume it will be the same */
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+ if (!rng->last_seeding)
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+ return 0;
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+
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+ rng->seed_save_len = 0;
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+ ret = clk_prepare_enable(rng->clk);
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+ if (ret)
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+ return ret;
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+
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+ /* Get new random numbers and store them for seeding on resume. */
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+ exynos_rng_get_random(rng, rng->seed_save, sizeof(rng->seed_save),
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+ &(rng->seed_save_len));
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+ dev_dbg(rng->dev, "Stored %u bytes for seeding on system resume\n",
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+ rng->seed_save_len);
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+
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+ clk_disable_unprepare(rng->clk);
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+
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+ return 0;
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+}
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+
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+static int __maybe_unused exynos_rng_resume(struct device *dev)
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+{
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+ struct platform_device *pdev = to_platform_device(dev);
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+ struct exynos_rng_dev *rng = platform_get_drvdata(pdev);
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+ int ret;
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+
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+ /* Never seeded so nothing to do */
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+ if (!rng->last_seeding)
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+ return 0;
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+
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+ ret = clk_prepare_enable(rng->clk);
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+ if (ret)
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+ return ret;
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+
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+ ret = exynos_rng_set_seed(rng, rng->seed_save, rng->seed_save_len);
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+
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+ clk_disable_unprepare(rng->clk);
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+
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+ return ret;
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+}
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+
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+static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend,
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+ exynos_rng_resume);
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+
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+static const struct of_device_id exynos_rng_dt_match[] = {
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+ {
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+ .compatible = "samsung,exynos4-rng",
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+ },
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+ { },
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+};
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+MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);
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+
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+static struct platform_driver exynos_rng_driver = {
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+ .driver = {
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+ .name = "exynos-rng",
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+ .pm = &exynos_rng_pm_ops,
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+ .of_match_table = exynos_rng_dt_match,
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+ },
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+ .probe = exynos_rng_probe,
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+ .remove = exynos_rng_remove,
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+};
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+
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+module_platform_driver(exynos_rng_driver);
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+
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+MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver");
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+MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>");
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+MODULE_LICENSE("GPL");
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Krzysztof Kozlowski