text: /*
   * 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_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_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) {
  		dev_node = of_find_compatible_node(NULL, NULL, "fsl,sec4.0");
  		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");
  