[PATCH v2 3/3] crypto: caam: add RNG support

[Steffen Trumtrar <s.trumtrar@pengutronix.de>]

Add suport for the i.MX6 CAAM RNG module.
The device is registered as a char-device under /dev/hwrng to mimic the
linux userspace interface.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/crypto/caam/Kconfig   |   7 +
 drivers/crypto/caam/Makefile  |   1 +
 drivers/crypto/caam/caamrng.c | 313 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 321 insertions(+)
 create mode 100644 drivers/crypto/caam/caamrng.c

diff --git a/drivers/crypto/caam/Kconfig b/drivers/crypto/caam/Kconfig
index d54754c7a89b..4bf1c937c9a5 100644
--- a/drivers/crypto/caam/Kconfig
+++ b/drivers/crypto/caam/Kconfig
@@ -35,3 +35,10 @@ config CRYPTO_DEV_FSL_CAAM_RINGSIZE
 		7 => 128
 		8 => 256
 		9 => 512
+
+config CRYPTO_DEV_FSL_CAAM_RNG
+	bool "Register caam RNG device"
+	depends on CRYPTO_DEV_FSL_CAAM && CRYPTO_DEV_FSL_CAAM_JR
+	default n
+	help
+	  Selecting this will register the SEC4 hardware rng.
diff --git a/drivers/crypto/caam/Makefile b/drivers/crypto/caam/Makefile
index cd46936fb6b4..ea63f5894441 100644
--- a/drivers/crypto/caam/Makefile
+++ b/drivers/crypto/caam/Makefile
@@ -3,3 +3,4 @@
 #
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM) += ctrl.o error.o
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM_JR) += jr.o
+obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM_RNG) += caamrng.o
diff --git a/drivers/crypto/caam/caamrng.c b/drivers/crypto/caam/caamrng.c
new file mode 100644
index 000000000000..fc1ed3f4987c
--- /dev/null
+++ b/drivers/crypto/caam/caamrng.c
@@ -0,0 +1,313 @@
+/*
+ * caam - Freescale FSL CAAM support for hw_random
+ *
+ * Copyright (C) 2011-2015 Freescale Semiconductor, Inc.
+ *
+ * Based on caamalg.c crypto API driver.
+ *
+ * relationship between job descriptors to shared descriptors:
+ *
+ * ---------------                     --------------
+ * | JobDesc #0  |-------------------->| ShareDesc  |
+ * | *(buffer 0) |      |------------->| (generate) |
+ * ---------------      |              | (move)     |
+ *                      |              | (store)    |
+ * ---------------      |              --------------
+ * | JobDesc #1  |------|
+ * | *(buffer 1) |
+ * ---------------
+ *
+ * A job desc looks like this:
+ *
+ * ---------------------
+ * | Header            |
+ * | ShareDesc Pointer |
+ * | SEQ_OUT_PTR       |
+ * | (output buffer)   |
+ * ---------------------
+ *
+ * The SharedDesc never changes, and each job descriptor points to one of two
+ * buffers for each device, from which the data will be copied into the
+ * requested destination
+ */
+#include <common.h>
+#include <dma.h>
+#include <driver.h>
+#include <init.h>
+
+#include "regs.h"
+#include "intern.h"
+#include "desc_constr.h"
+#include "jr.h"
+#include "error.h"
+
+/*
+ * Maximum buffer size: maximum number of random, cache-aligned bytes that
+ * will be generated and moved to seq out ptr (extlen not allowed)
+ */
+#define RN_BUF_SIZE			32767
+
+/* length of descriptors */
+#define DESC_JOB_O_LEN			(CAAM_CMD_SZ * 2 + CAAM_PTR_SZ * 2)
+#define DESC_RNG_LEN			(10 * CAAM_CMD_SZ)
+
+/* Buffer, its dma address and lock */
+struct buf_data {
+	u8 buf[RN_BUF_SIZE];
+	dma_addr_t addr;
+	u32 hw_desc[DESC_JOB_O_LEN];
+#define BUF_NOT_EMPTY 0
+#define BUF_EMPTY 1
+#define BUF_PENDING 2  /* Empty, but with job pending --don't submit another */
+	int empty;
+};
+
+/* rng per-device context */
+struct caam_rng_ctx {
+	struct device_d *jrdev;
+	dma_addr_t sh_desc_dma;
+	u32 sh_desc[DESC_RNG_LEN];
+	unsigned int cur_buf_idx;
+	int current_buf;
+	struct buf_data bufs[2];
+	struct cdev cdev;
+};
+
+static struct caam_rng_ctx *rng_ctx;
+
+static void rng_done(struct device_d *jrdev, u32 *desc, u32 err, void *context)
+{
+	struct buf_data *bd;
+
+	bd = (struct buf_data *)((char *)desc -
+	      offsetof(struct buf_data, hw_desc));
+
+	if (err)
+		caam_jr_strstatus(jrdev, err);
+
+	bd->empty = BUF_NOT_EMPTY;
+
+	/* Buffer refilled, invalidate cache */
+	dma_sync_single_for_cpu(bd->addr, RN_BUF_SIZE, DMA_FROM_DEVICE);
+
+#ifdef DEBUG
+	print_hex_dump(KERN_ERR, "rng refreshed buf@: ",
+		       DUMP_PREFIX_OFFSET, 16, 4, bd->buf, RN_BUF_SIZE, 1);
+#endif
+}
+
+static inline int submit_job(struct caam_rng_ctx *ctx, int to_current)
+{
+	struct buf_data *bd = &ctx->bufs[!(to_current ^ ctx->current_buf)];
+	struct device_d *jrdev = ctx->jrdev;
+	u32 *desc = bd->hw_desc;
+	int err;
+
+	dev_dbg(jrdev, "submitting job %d\n", !(to_current ^ ctx->current_buf));
+
+	dma_sync_single_for_device((unsigned long)desc, desc_bytes(desc), DMA_TO_DEVICE);
+
+	err = caam_jr_enqueue(jrdev, desc, rng_done, ctx);
+	if (!err)
+		bd->empty += 1; /* note if pending */
+
+	return err;
+}
+
+static int caam_read(struct caam_rng_ctx *ctx, void *data, size_t max, bool wait)
+{
+	struct buf_data *bd = &ctx->bufs[ctx->current_buf];
+	int next_buf_idx, copied_idx;
+	int err;
+
+	if (bd->empty) {
+		/* try to submit job if there wasn't one */
+		if (bd->empty == BUF_EMPTY) {
+			err = submit_job(ctx, 1);
+			/* if can't submit job, can't even wait */
+			if (err)
+				return 0;
+		}
+		/* no immediate data, so exit if not waiting */
+		if (!wait)
+			return 0;
+	}
+
+	next_buf_idx = ctx->cur_buf_idx + max;
+	dev_dbg(ctx->jrdev, "%s: start reading at buffer %d, idx %d\n",
+		 __func__, ctx->current_buf, ctx->cur_buf_idx);
+
+	/* if enough data in current buffer */
+	if (next_buf_idx < RN_BUF_SIZE) {
+		memcpy(data, bd->buf + ctx->cur_buf_idx, max);
+		ctx->cur_buf_idx = next_buf_idx;
+		return max;
+	}
+
+	/* else, copy what's left... */
+	copied_idx = RN_BUF_SIZE - ctx->cur_buf_idx;
+	memcpy(data, bd->buf + ctx->cur_buf_idx, copied_idx);
+	ctx->cur_buf_idx = 0;
+	bd->empty = BUF_EMPTY;
+
+	/* ...refill... */
+	submit_job(ctx, 1);
+
+	/* and use next buffer */
+	ctx->current_buf = !ctx->current_buf;
+	dev_dbg(ctx->jrdev, "switched to buffer %d\n", ctx->current_buf);
+
+	/* since there already is some data read, don't wait */
+	return copied_idx + caam_read(ctx, data + copied_idx,
+				      max - copied_idx, false);
+}
+
+static inline int rng_create_sh_desc(struct caam_rng_ctx *ctx)
+{
+	u32 *desc = ctx->sh_desc;
+
+	init_sh_desc(desc, HDR_SHARE_SERIAL);
+
+	/* Propagate errors from shared to job descriptor */
+	append_cmd(desc, SET_OK_NO_PROP_ERRORS | CMD_LOAD);
+
+	/* Generate random bytes */
+	append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG);
+
+	/* Store bytes */
+	append_seq_fifo_store(desc, RN_BUF_SIZE, FIFOST_TYPE_RNGSTORE);
+
+	ctx->sh_desc_dma = (dma_addr_t)desc;
+
+	dma_sync_single_for_device((unsigned long)desc, desc_bytes(desc), DMA_TO_DEVICE);
+#ifdef DEBUG
+	print_hex_dump(KERN_ERR, "rng shdesc@: ", DUMP_PREFIX_OFFSET, 16, 4,
+		       desc, desc_bytes(desc), 1);
+#endif
+	return 0;
+}
+
+static inline int rng_create_job_desc(struct caam_rng_ctx *ctx, int buf_id)
+{
+	struct buf_data *bd = &ctx->bufs[buf_id];
+	u32 *desc = bd->hw_desc;
+	int sh_len = desc_len(ctx->sh_desc);
+
+	init_job_desc_shared(desc, ctx->sh_desc_dma, sh_len, HDR_SHARE_DEFER |
+			     HDR_REVERSE);
+
+	bd->addr = (dma_addr_t)bd->buf;
+
+	append_seq_out_ptr_intlen(desc, bd->addr, RN_BUF_SIZE, 0);
+#ifdef DEBUG
+	print_hex_dump(KERN_ERR, "rng job desc@: ", DUMP_PREFIX_OFFSET, 16, 4,
+		       desc, desc_bytes(desc), 1);
+#endif
+	return 0;
+}
+
+static int caam_init_buf(struct caam_rng_ctx *ctx, int buf_id)
+{
+	struct buf_data *bd = &ctx->bufs[buf_id];
+	int err;
+
+	err = rng_create_job_desc(ctx, buf_id);
+	if (err)
+		return err;
+
+	bd->empty = BUF_EMPTY;
+	submit_job(ctx, buf_id == ctx->current_buf);
+
+	return 0;
+}
+
+static int caam_init_rng(struct caam_rng_ctx *ctx, struct device_d *jrdev)
+{
+	int err;
+
+	ctx->jrdev = jrdev;
+
+	err = rng_create_sh_desc(ctx);
+	if (err)
+		return err;
+
+	ctx->current_buf = 0;
+	ctx->cur_buf_idx = 0;
+
+	err = caam_init_buf(ctx, 0);
+	if (err)
+		return err;
+
+	err = caam_init_buf(ctx, 1);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static ssize_t random_read(struct cdev *cdev, void *buf, size_t count, loff_t offset, ulong flags)
+{
+	struct caam_rng_ctx *ctx = container_of(cdev, struct caam_rng_ctx, cdev);
+
+	return caam_read(ctx, buf, count, true);
+}
+
+static struct file_operations randomops = {
+	.read  = random_read,
+	.lseek = dev_lseek_default,
+};
+
+static int caam_init_devrandom(struct caam_rng_ctx *ctx, struct device_d *jrdev)
+{
+	ctx->cdev.name = "hwrng";
+	ctx->cdev.flags = DEVFS_IS_CHARACTER_DEV;
+	ctx->cdev.ops = &randomops;
+	ctx->cdev.dev = jrdev;
+
+	return devfs_create(&ctx->cdev);
+}
+
+static int caam_rng_probe(struct device_d *d)
+{
+	struct device_d *dev;
+	struct device_node *dev_node;
+	int err;
+
+	dev_node = of_find_compatible_node(NULL, NULL, "fsl,sec-v4.0-job-ring");
+	if (!dev_node) {
+		dev_node = of_find_compatible_node(NULL, NULL, "fsl,sec4.0-job-ring");
+		if (!dev_node)
+			return -ENODEV;
+	}
+
+	dev = of_find_device_by_node(dev_node);
+	if (!dev)
+		return -ENODEV;
+	rng_ctx = xzalloc(sizeof(*rng_ctx));
+
+	err = caam_init_rng(rng_ctx, dev);
+	if (err)
+		return err;
+
+	err = caam_init_devrandom(rng_ctx, dev);
+	if (err)
+		return err;
+
+	dev_info(d, "registering rng-caam\n");
+
+	return 0;
+}
+
+static struct of_device_id caam_rng_ids[] = {
+	{
+		.compatible = "caam_rng",
+	},
+	{},
+};
+
+static struct driver_d caam_rng_driver = {
+	.name = "caam_rng",
+	.of_compatible = DRV_OF_COMPAT(caam_rng_ids),
+	.probe = caam_rng_probe,
+};
+device_platform_driver(caam_rng_driver);
-- 
2.7.0.rc3


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