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 * 10) >> 5) /* quality: 10/32 */
 26
 27static DECLARE_WAIT_QUEUE_HEAD(rng_queue);
 28
 29static int ath9k_rng_data_read(struct ath_softc *sc, u32 *buf, u32 buf_size)
 30{
 31	int i, j;
 32	u32  v1, v2, rng_last = sc->rng_last;
 33	struct ath_hw *ah = sc->sc_ah;
 34
 35	ath9k_ps_wakeup(sc);
 36
 37	REG_RMW_FIELD(ah, AR_PHY_TEST, AR_PHY_TEST_BBB_OBS_SEL, 1);
 38	REG_CLR_BIT(ah, AR_PHY_TEST, AR_PHY_TEST_RX_OBS_SEL_BIT5);
 39	REG_RMW_FIELD(ah, AR_PHY_TEST_CTL_STATUS, AR_PHY_TEST_CTL_RX_OBS_SEL, 0);
 40
 41	for (i = 0, j = 0; i < buf_size; i++) {
 42		v1 = REG_READ(ah, AR_PHY_TST_ADC) & 0xffff;
 43		v2 = REG_READ(ah, AR_PHY_TST_ADC) & 0xffff;
 44
 45		/* wait for data ready */
 46		if (v1 && v2 && rng_last != v1 && v1 != v2 && v1 != 0xffff &&
 47		    v2 != 0xffff)
 48			buf[j++] = (v1 << 16) | v2;
 49
 50		rng_last = v2;
 51	}
 52
 53	ath9k_ps_restore(sc);
 54
 55	sc->rng_last = rng_last;
 56
 57	return j << 2;
 58}
 59
 60static u32 ath9k_rng_delay_get(u32 fail_stats)
 61{
 62	u32 delay;
 63
 64	if (fail_stats < 100)
 65		delay = 10;
 66	else if (fail_stats < 105)
 67		delay = 1000;
 68	else
 69		delay = 10000;
 70
 71	return delay;
 72}
 73
 74static int ath9k_rng_kthread(void *data)
 75{
 76	int bytes_read;
 77	struct ath_softc *sc = data;
 78	u32 *rng_buf;
 79	u32 delay, fail_stats = 0;
 80
 81	rng_buf = kmalloc_array(ATH9K_RNG_BUF_SIZE, sizeof(u32), GFP_KERNEL);
 82	if (!rng_buf)
 83		goto out;
 84
 85	while (!kthread_should_stop()) {
 86		bytes_read = ath9k_rng_data_read(sc, rng_buf,
 87						 ATH9K_RNG_BUF_SIZE);
 88		if (unlikely(!bytes_read)) {
 89			delay = ath9k_rng_delay_get(++fail_stats);
 90			wait_event_interruptible_timeout(rng_queue,
 91							 kthread_should_stop(),
 92							 msecs_to_jiffies(delay));
 93			continue;
 94		}
 95
 96		fail_stats = 0;
 97
 98		/* sleep until entropy bits under write_wakeup_threshold */
 99		add_hwgenerator_randomness((void *)rng_buf, bytes_read,
100					   ATH9K_RNG_ENTROPY(bytes_read));
101	}
102
103	kfree(rng_buf);
104out:
105	sc->rng_task = NULL;
106
107	return 0;
108}
109
110void ath9k_rng_start(struct ath_softc *sc)
111{
112	struct ath_hw *ah = sc->sc_ah;
113
114	if (sc->rng_task)
115		return;
116
117	if (!AR_SREV_9300_20_OR_LATER(ah))
118		return;
119
120	sc->rng_task = kthread_run(ath9k_rng_kthread, sc, "ath9k-hwrng");
121	if (IS_ERR(sc->rng_task))
122		sc->rng_task = NULL;
123}
124
125void ath9k_rng_stop(struct ath_softc *sc)
126{
127	if (sc->rng_task) {
128		kthread_stop(sc->rng_task);
129		sc->rng_task = NULL;
130	}
131}