crypto: caam - hwrng support

caam_read copies random bytes from two buffers into output.

caam rng can fill empty buffer 0xffff bytes at a time,
but the buffer sizes are rounded down to multiple of cacheline size.

Signed-off-by: Yuan Kang <Yuan.Kang@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/caam/Kconfig

@@ -82,3 +82,16 @@ config CRYPTO_DEV_FSL_CAAM_AHASH_API
 
 	  To compile this as a module, choose M here: the module
 	  will be called caamhash.
+
+config CRYPTO_DEV_FSL_CAAM_RNG_API
+	tristate "Register caam device for hwrng API"
+	depends on CRYPTO_DEV_FSL_CAAM
+	default y
+	select CRYPTO_RNG
+	select HW_RANDOM
+	help
+	  Selecting this will register the SEC4 hardware rng to
+	  the hw_random API for suppying the kernel entropy pool.
+
+	  To compile this as a module, choose M here: the module
+	  will be called caamrng.

drivers/crypto/caam/Makefile

@@ -5,5 +5,6 @@
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM) += caam.o
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM_CRYPTO_API) += caamalg.o
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM_AHASH_API) += caamhash.o
+obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM_RNG_API) += caamrng.o
 
 caam-objs := ctrl.o jr.o error.o key_gen.o

drivers/crypto/caam/caamrng.c

@@ -0,0 +1,309 @@
+/*
+ * caam - Freescale FSL CAAM support for hw_random
+ *
+ * Copyright 2011 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 <linux/hw_random.h>
+#include <linux/completion.h>
+#include <linux/atomic.h>
+
+#include "compat.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			(0xffff / L1_CACHE_BYTES * \
+					 L1_CACHE_BYTES)
+
+/* 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;
+	struct completion filled;
+	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 */
+	atomic_t empty;
+};
+
+/* rng per-device context */
+struct caam_rng_ctx {
+	struct device *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];
+};
+
+static struct caam_rng_ctx rng_ctx;
+
+static inline void rng_unmap_buf(struct device *jrdev, struct buf_data *bd)
+{
+	if (bd->addr)
+		dma_unmap_single(jrdev, bd->addr, RN_BUF_SIZE,
+				 DMA_FROM_DEVICE);
+}
+
+static inline void rng_unmap_ctx(struct caam_rng_ctx *ctx)
+{
+	struct device *jrdev = ctx->jrdev;
+
+	if (ctx->sh_desc_dma)
+		dma_unmap_single(jrdev, ctx->sh_desc_dma, DESC_RNG_LEN,
+				 DMA_TO_DEVICE);
+	rng_unmap_buf(jrdev, &ctx->bufs[0]);
+	rng_unmap_buf(jrdev, &ctx->bufs[1]);
+}
+
+static void rng_done(struct device *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) {
+		char tmp[CAAM_ERROR_STR_MAX];
+
+		dev_err(jrdev, "%08x: %s\n", err, caam_jr_strstatus(tmp, err));
+	}
+
+	atomic_set(&bd->empty, BUF_NOT_EMPTY);
+	complete(&bd->filled);
+#ifdef DEBUG
+	print_hex_dump(KERN_ERR, "rng refreshed buf@: ",
+		       DUMP_PREFIX_ADDRESS, 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 *jrdev = ctx->jrdev;
+	u32 *desc = bd->hw_desc;
+	int err;
+
+	dev_dbg(jrdev, "submitting job %d\n", !(to_current ^ ctx->current_buf));
+	init_completion(&bd->filled);
+	err = caam_jr_enqueue(jrdev, desc, rng_done, ctx);
+	if (err)
+		complete(&bd->filled); /* don't wait on failed job*/
+	else
+		atomic_inc(&bd->empty); /* note if pending */
+
+	return err;
+}
+
+static int caam_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct caam_rng_ctx *ctx = &rng_ctx;
+	struct buf_data *bd = &ctx->bufs[ctx->current_buf];
+	int next_buf_idx, copied_idx;
+	int err;
+
+	if (atomic_read(&bd->empty)) {
+		/* try to submit job if there wasn't one */
+		if (atomic_read(&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;
+
+		/* waiting for pending job */
+		if (atomic_read(&bd->empty))
+			wait_for_completion(&bd->filled);
+	}
+
+	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;
+	atomic_set(&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(rng, data + copied_idx,
+				      max - copied_idx, false);
+}
+
+static inline void rng_create_sh_desc(struct caam_rng_ctx *ctx)
+{
+	struct device *jrdev = ctx->jrdev;
+	u32 *desc = ctx->sh_desc;
+
+	init_sh_desc(desc, HDR_SHARE_WAIT);
+
+	/* 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_map_single(jrdev, desc, desc_bytes(desc),
+					  DMA_TO_DEVICE);
+#ifdef DEBUG
+	print_hex_dump(KERN_ERR, "rng shdesc@: ", DUMP_PREFIX_ADDRESS, 16, 4,
+		       desc, desc_bytes(desc), 1);
+#endif
+}
+
+static inline void rng_create_job_desc(struct caam_rng_ctx *ctx, int buf_id)
+{
+	struct device *jrdev = ctx->jrdev;
+	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_map_single(jrdev, bd->buf, RN_BUF_SIZE, DMA_FROM_DEVICE);
+
+	append_seq_out_ptr_intlen(desc, bd->addr, RN_BUF_SIZE, 0);
+#ifdef DEBUG
+	print_hex_dump(KERN_ERR, "rng job desc@: ", DUMP_PREFIX_ADDRESS, 16, 4,
+		       desc, desc_bytes(desc), 1);
+#endif
+}
+
+static void caam_cleanup(struct hwrng *rng)
+{
+	int i;
+	struct buf_data *bd;
+
+	for (i = 0; i < 2; i++) {
+		bd = &rng_ctx.bufs[i];
+		if (atomic_read(&bd->empty) == BUF_PENDING)
+			wait_for_completion(&bd->filled);
+	}
+
+	rng_unmap_ctx(&rng_ctx);
+}
+
+static void caam_init_buf(struct caam_rng_ctx *ctx, int buf_id)
+{
+	struct buf_data *bd = &ctx->bufs[buf_id];
+
+	rng_create_job_desc(ctx, buf_id);
+	atomic_set(&bd->empty, BUF_EMPTY);
+	submit_job(ctx, buf_id == ctx->current_buf);
+	wait_for_completion(&bd->filled);
+}
+
+static void caam_init_rng(struct caam_rng_ctx *ctx, struct device *jrdev)
+{
+	ctx->jrdev = jrdev;
+	rng_create_sh_desc(ctx);
+	ctx->current_buf = 0;
+	ctx->cur_buf_idx = 0;
+	caam_init_buf(ctx, 0);
+	caam_init_buf(ctx, 1);
+}
+
+static struct hwrng caam_rng = {
+	.name		= "rng-caam",
+	.cleanup	= caam_cleanup,
+	.read		= caam_read,
+};
+
+static void __exit caam_rng_exit(void)
+{
+	hwrng_unregister(&caam_rng);
+}
+
+static int __init caam_rng_init(void)
+{
+	struct device_node *dev_node;
+	struct platform_device *pdev;
+	struct device *ctrldev;
+	struct caam_drv_private *priv;
+
+	dev_node = of_find_compatible_node(NULL, NULL, "fsl,sec-v4.0");
+	if (!dev_node)
+		return -ENODEV;
+
+	pdev = of_find_device_by_node(dev_node);
+	if (!pdev)
+		return -ENODEV;
+
+	ctrldev = &pdev->dev;
+	priv = dev_get_drvdata(ctrldev);
+	of_node_put(dev_node);
+
+	caam_init_rng(&rng_ctx, priv->jrdev[0]);
+
+	dev_info(priv->jrdev[0], "registering rng-caam\n");
+	return hwrng_register(&caam_rng);
+}
+
+module_init(caam_rng_init);
+module_exit(caam_rng_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("FSL CAAM support for hw_random API");
+MODULE_AUTHOR("Freescale Semiconductor - NMG");