caamrng.c

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/*
 * 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");