drivers/net/wireless/ath/ath9k/rng.c

   1 /*
   2  * Copyright (c) 2015 Qualcomm Atheros, Inc.
   3  *
   4  * Permission to use, copy, modify, and/or distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16
  17 #include <linux/hw_random.h>
  18 #include <linux/kthread.h>
  19
  20 #include "ath9k.h"
  21 #include "hw.h"
  22 #include "ar9003_phy.h"
  23
  24 #define ATH9K_RNG_BUF_SIZE      320
  25 #define ATH9K_RNG_ENTROPY(x)    (((x) * 8 * 320) >> 10) /* quality: 320/1024 */
  26
  27 static int ath9k_rng_data_read(struct ath_softc *sc, u32 *buf, u32 buf_size)
  28 {
  29         int i, j;
  30         u32  v1, v2, rng_last = sc->rng_last;
  31         struct ath_hw *ah = sc->sc_ah;
  32
  33         ath9k_ps_wakeup(sc);
  34
  35         REG_RMW_FIELD(ah, AR_PHY_TEST, AR_PHY_TEST_BBB_OBS_SEL, 1);
  36         REG_CLR_BIT(ah, AR_PHY_TEST, AR_PHY_TEST_RX_OBS_SEL_BIT5);
  37         REG_RMW_FIELD(ah, AR_PHY_TEST_CTL_STATUS, AR_PHY_TEST_CTL_RX_OBS_SEL, 0);
  38
  39         for (i = 0, j = 0; i < buf_size; i++) {
  40                 v1 = REG_READ(ah, AR_PHY_TST_ADC) & 0xffff;
  41                 v2 = REG_READ(ah, AR_PHY_TST_ADC) & 0xffff;
  42
  43                 /* wait for data ready */
  44                 if (v1 && v2 && rng_last != v1 && v1 != v2 && v1 != 0xffff &&
  45                     v2 != 0xffff)
  46                         buf[j++] = (v1 << 16) | v2;
  47
  48                 rng_last = v2;
  49         }
  50
  51         ath9k_ps_restore(sc);
  52
  53         sc->rng_last = rng_last;
  54
  55         return j << 2;
  56 }
  57
  58 static u32 ath9k_rng_delay_get(u32 fail_stats)
  59 {
  60         u32 delay;
  61
  62         if (fail_stats < 100)
  63                 delay = 10;
  64         else if (fail_stats < 105)
  65                 delay = 1000;
  66         else
  67                 delay = 10000;
  68
  69         return delay;
  70 }
  71
  72 static int ath9k_rng_kthread(void *data)
  73 {
  74         int bytes_read;
  75         struct ath_softc *sc = data;
  76         u32 *rng_buf;
  77         u32 delay, fail_stats = 0;
  78
  79         rng_buf = kmalloc_array(ATH9K_RNG_BUF_SIZE, sizeof(u32), GFP_KERNEL);
  80         if (!rng_buf)
  81                 goto out;
  82
  83         while (!kthread_should_stop()) {
  84                 bytes_read = ath9k_rng_data_read(sc, rng_buf,
  85                                                  ATH9K_RNG_BUF_SIZE);
  86                 if (unlikely(!bytes_read)) {
  87                         delay = ath9k_rng_delay_get(++fail_stats);
  88                         msleep_interruptible(delay);
  89                         continue;
  90                 }
  91
  92                 fail_stats = 0;
  93
  94                 /* sleep until entropy bits under write_wakeup_threshold */
  95                 add_hwgenerator_randomness((void *)rng_buf, bytes_read,
  96                                            ATH9K_RNG_ENTROPY(bytes_read));
  97         }
  98
  99         kfree(rng_buf);
 100 out:
 101         sc->rng_task = NULL;
 102
 103         return 0;
 104 }
 105
 106 void ath9k_rng_start(struct ath_softc *sc)
 107 {
 108         struct ath_hw *ah = sc->sc_ah;
 109
 110         if (sc->rng_task)
 111                 return;
 112
 113         if (!AR_SREV_9300_20_OR_LATER(ah))
 114                 return;
 115
 116         sc->rng_task = kthread_run(ath9k_rng_kthread, sc, "ath9k-hwrng");
 117         if (IS_ERR(sc->rng_task))
 118                 sc->rng_task = NULL;
 119 }
 120
 121 void ath9k_rng_stop(struct ath_softc *sc)
 122 {
 123         if (sc->rng_task)
 124                 kthread_stop(sc->rng_task);
 125 }