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
ath9k_rng_data_read(struct ath_softc * sc,u32 * buf,u32 buf_size)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
ath9k_rng_delay_get(u32 fail_stats)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
ath9k_rng_kthread(void * data)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
ath9k_rng_start(struct ath_softc * sc)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
ath9k_rng_stop(struct ath_softc * sc)121 void ath9k_rng_stop(struct ath_softc *sc)
122 {
123 if (sc->rng_task) {
124 kthread_stop(sc->rng_task);
125 sc->rng_task = NULL;
126 }
127 }
128