drivers/crypto/caam/caamrng.c

   1 /*
   2  * caam - Freescale FSL CAAM support for hw_random
   3  *
   4  * Copyright 2011 Freescale Semiconductor, Inc.
   5  *
   6  * Based on caamalg.c crypto API driver.
   7  *
   8  * relationship between job descriptors to shared descriptors:
   9  *
  10  * ---------------                     --------------
  11  * | JobDesc #0  |-------------------->| ShareDesc  |
  12  * | *(buffer 0) |      |------------->| (generate) |
  13  * ---------------      |              | (move)     |
  14  *                      |              | (store)    |
  15  * ---------------      |              --------------
  16  * | JobDesc #1  |------|
  17  * | *(buffer 1) |
  18  * ---------------
  19  *
  20  * A job desc looks like this:
  21  *
  22  * ---------------------
  23  * | Header            |
  24  * | ShareDesc Pointer |
  25  * | SEQ_OUT_PTR       |
  26  * | (output buffer)   |
  27  * ---------------------
  28  *
  29  * The SharedDesc never changes, and each job descriptor points to one of two
  30  * buffers for each device, from which the data will be copied into the
  31  * requested destination
  32  */
  33
  34 #include <linux/hw_random.h>
  35 #include <linux/completion.h>
  36 #include <linux/atomic.h>
  37
  38 #include "compat.h"
  39
  40 #include "regs.h"
  41 #include "intern.h"
  42 #include "desc_constr.h"
  43 #include "jr.h"
  44 #include "error.h"
  45
  46 /*
  47  * Maximum buffer size: maximum number of random, cache-aligned bytes that
  48  * will be generated and moved to seq out ptr (extlen not allowed)
  49  */
  50 #define RN_BUF_SIZE                     (0xffff / L1_CACHE_BYTES * \
  51                                          L1_CACHE_BYTES)
  52
  53 /* length of descriptors */
  54 #define DESC_JOB_O_LEN                  (CAAM_CMD_SZ * 2 + CAAM_PTR_SZ * 2)
  55 #define DESC_RNG_LEN                    (10 * CAAM_CMD_SZ)
  56
  57 /* Buffer, its dma address and lock */
  58 struct buf_data {
  59         u8 buf[RN_BUF_SIZE];
  60         dma_addr_t addr;
  61         struct completion filled;
  62         u32 hw_desc[DESC_JOB_O_LEN];
  63 #define BUF_NOT_EMPTY 0
  64 #define BUF_EMPTY 1
  65 #define BUF_PENDING 2  /* Empty, but with job pending --don't submit another */
  66         atomic_t empty;
  67 };
  68
  69 /* rng per-device context */
  70 struct caam_rng_ctx {
  71         struct device *jrdev;
  72         dma_addr_t sh_desc_dma;
  73         u32 sh_desc[DESC_RNG_LEN];
  74         unsigned int cur_buf_idx;
  75         int current_buf;
  76         struct buf_data bufs[2];
  77 };
  78
  79 static struct caam_rng_ctx rng_ctx;
  80
  81 static inline void rng_unmap_buf(struct device *jrdev, struct buf_data *bd)
  82 {
  83         if (bd->addr)
  84                 dma_unmap_single(jrdev, bd->addr, RN_BUF_SIZE,
  85                                  DMA_FROM_DEVICE);
  86 }
  87
  88 static inline void rng_unmap_ctx(struct caam_rng_ctx *ctx)
  89 {
  90         struct device *jrdev = ctx->jrdev;
  91
  92         if (ctx->sh_desc_dma)
  93                 dma_unmap_single(jrdev, ctx->sh_desc_dma, DESC_RNG_LEN,
  94                                  DMA_TO_DEVICE);
  95         rng_unmap_buf(jrdev, &ctx->bufs[0]);
  96         rng_unmap_buf(jrdev, &ctx->bufs[1]);
  97 }
  98
  99 static void rng_done(struct device *jrdev, u32 *desc, u32 err, void *context)
 100 {
 101         struct buf_data *bd;
 102
 103         bd = (struct buf_data *)((char *)desc -
 104               offsetof(struct buf_data, hw_desc));
 105
 106         if (err) {
 107                 char tmp[CAAM_ERROR_STR_MAX];
 108
 109                 dev_err(jrdev, "%08x: %s\n", err, caam_jr_strstatus(tmp, err));
 110         }
 111
 112         atomic_set(&bd->empty, BUF_NOT_EMPTY);
 113         complete(&bd->filled);
 114 #ifdef DEBUG
 115         print_hex_dump(KERN_ERR, "rng refreshed buf@: ",
 116                        DUMP_PREFIX_ADDRESS, 16, 4, bd->buf, RN_BUF_SIZE, 1);
 117 #endif
 118 }
 119
 120 static inline int submit_job(struct caam_rng_ctx *ctx, int to_current)
 121 {
 122         struct buf_data *bd = &ctx->bufs[!(to_current ^ ctx->current_buf)];
 123         struct device *jrdev = ctx->jrdev;
 124         u32 *desc = bd->hw_desc;
 125         int err;
 126
 127         dev_dbg(jrdev, "submitting job %d\n", !(to_current ^ ctx->current_buf));
 128         init_completion(&bd->filled);
 129         err = caam_jr_enqueue(jrdev, desc, rng_done, ctx);
 130         if (err)
 131                 complete(&bd->filled); /* don't wait on failed job*/
 132         else
 133                 atomic_inc(&bd->empty); /* note if pending */
 134
 135         return err;
 136 }
 137
 138 static int caam_read(struct hwrng *rng, void *data, size_t max, bool wait)
 139 {
 140         struct caam_rng_ctx *ctx = &rng_ctx;
 141         struct buf_data *bd = &ctx->bufs[ctx->current_buf];
 142         int next_buf_idx, copied_idx;
 143         int err;
 144
 145         if (atomic_read(&bd->empty)) {
 146                 /* try to submit job if there wasn't one */
 147                 if (atomic_read(&bd->empty) == BUF_EMPTY) {
 148                         err = submit_job(ctx, 1);
 149                         /* if can't submit job, can't even wait */
 150                         if (err)
 151                                 return 0;
 152                 }
 153                 /* no immediate data, so exit if not waiting */
 154                 if (!wait)
 155                         return 0;
 156
 157                 /* waiting for pending job */
 158                 if (atomic_read(&bd->empty))
 159                         wait_for_completion(&bd->filled);
 160         }
 161
 162         next_buf_idx = ctx->cur_buf_idx + max;
 163         dev_dbg(ctx->jrdev, "%s: start reading at buffer %d, idx %d\n",
 164                  __func__, ctx->current_buf, ctx->cur_buf_idx);
 165
 166         /* if enough data in current buffer */
 167         if (next_buf_idx < RN_BUF_SIZE) {
 168                 memcpy(data, bd->buf + ctx->cur_buf_idx, max);
 169                 ctx->cur_buf_idx = next_buf_idx;
 170                 return max;
 171         }
 172
 173         /* else, copy what's left... */
 174         copied_idx = RN_BUF_SIZE - ctx->cur_buf_idx;
 175         memcpy(data, bd->buf + ctx->cur_buf_idx, copied_idx);
 176         ctx->cur_buf_idx = 0;
 177         atomic_set(&bd->empty, BUF_EMPTY);
 178
 179         /* ...refill... */
 180         submit_job(ctx, 1);
 181
 182         /* and use next buffer */
 183         ctx->current_buf = !ctx->current_buf;
 184         dev_dbg(ctx->jrdev, "switched to buffer %d\n", ctx->current_buf);
 185
 186         /* since there already is some data read, don't wait */
 187         return copied_idx + caam_read(rng, data + copied_idx,
 188                                       max - copied_idx, false);
 189 }
 190
 191 static inline void rng_create_sh_desc(struct caam_rng_ctx *ctx)
 192 {
 193         struct device *jrdev = ctx->jrdev;
 194         u32 *desc = ctx->sh_desc;
 195
 196         init_sh_desc(desc, HDR_SHARE_SERIAL);
 197
 198         /* Propagate errors from shared to job descriptor */
 199         append_cmd(desc, SET_OK_NO_PROP_ERRORS | CMD_LOAD);
 200
 201         /* Generate random bytes */
 202         append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG);
 203
 204         /* Store bytes */
 205         append_seq_fifo_store(desc, RN_BUF_SIZE, FIFOST_TYPE_RNGSTORE);
 206
 207         ctx->sh_desc_dma = dma_map_single(jrdev, desc, desc_bytes(desc),
 208                                           DMA_TO_DEVICE);
 209 #ifdef DEBUG
 210         print_hex_dump(KERN_ERR, "rng shdesc@: ", DUMP_PREFIX_ADDRESS, 16, 4,
 211                        desc, desc_bytes(desc), 1);
 212 #endif
 213 }
 214
 215 static inline void rng_create_job_desc(struct caam_rng_ctx *ctx, int buf_id)
 216 {
 217         struct device *jrdev = ctx->jrdev;
 218         struct buf_data *bd = &ctx->bufs[buf_id];
 219         u32 *desc = bd->hw_desc;
 220         int sh_len = desc_len(ctx->sh_desc);
 221
 222         init_job_desc_shared(desc, ctx->sh_desc_dma, sh_len, HDR_SHARE_DEFER |
 223                              HDR_REVERSE);
 224
 225         bd->addr = dma_map_single(jrdev, bd->buf, RN_BUF_SIZE, DMA_FROM_DEVICE);
 226
 227         append_seq_out_ptr_intlen(desc, bd->addr, RN_BUF_SIZE, 0);
 228 #ifdef DEBUG
 229         print_hex_dump(KERN_ERR, "rng job desc@: ", DUMP_PREFIX_ADDRESS, 16, 4,
 230                        desc, desc_bytes(desc), 1);
 231 #endif
 232 }
 233
 234 static void caam_cleanup(struct hwrng *rng)
 235 {
 236         int i;
 237         struct buf_data *bd;
 238
 239         for (i = 0; i < 2; i++) {
 240                 bd = &rng_ctx.bufs[i];
 241                 if (atomic_read(&bd->empty) == BUF_PENDING)
 242                         wait_for_completion(&bd->filled);
 243         }
 244
 245         rng_unmap_ctx(&rng_ctx);
 246 }
 247
 248 static void caam_init_buf(struct caam_rng_ctx *ctx, int buf_id)
 249 {
 250         struct buf_data *bd = &ctx->bufs[buf_id];
 251
 252         rng_create_job_desc(ctx, buf_id);
 253         atomic_set(&bd->empty, BUF_EMPTY);
 254         submit_job(ctx, buf_id == ctx->current_buf);
 255         wait_for_completion(&bd->filled);
 256 }
 257
 258 static void caam_init_rng(struct caam_rng_ctx *ctx, struct device *jrdev)
 259 {
 260         ctx->jrdev = jrdev;
 261         rng_create_sh_desc(ctx);
 262         ctx->current_buf = 0;
 263         ctx->cur_buf_idx = 0;
 264         caam_init_buf(ctx, 0);
 265         caam_init_buf(ctx, 1);
 266 }
 267
 268 static struct hwrng caam_rng = {
 269         .name           = "rng-caam",
 270         .cleanup        = caam_cleanup,
 271         .read           = caam_read,
 272 };
 273
 274 static void __exit caam_rng_exit(void)
 275 {
 276         caam_jr_free(rng_ctx.jrdev);
 277         hwrng_unregister(&caam_rng);
 278 }
 279
 280 static int __init caam_rng_init(void)
 281 {
 282         struct device *dev;
 283
 284         dev = caam_jr_alloc();
 285         if (IS_ERR(dev)) {
 286                 pr_err("Job Ring Device allocation for transform failed\n");
 287                 return PTR_ERR(dev);
 288         }
 289
 290         caam_init_rng(&rng_ctx, dev);
 291
 292         dev_info(dev, "registering rng-caam\n");
 293         return hwrng_register(&caam_rng);
 294 }
 295
 296 module_init(caam_rng_init);
 297 module_exit(caam_rng_exit);
 298
 299 MODULE_LICENSE("GPL");
 300 MODULE_DESCRIPTION("FSL CAAM support for hw_random API");
 301 MODULE_AUTHOR("Freescale Semiconductor - NMG");