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
 27static 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
 58static int ath9k_rng_kthread(void *data)
 59{
 60	int bytes_read;
 61	struct ath_softc *sc = data;
 62	u32 *rng_buf;
 63
 64	rng_buf = kmalloc_array(ATH9K_RNG_BUF_SIZE, sizeof(u32), GFP_KERNEL);
 65	if (!rng_buf)
 66		goto out;
 67
 68	while (!kthread_should_stop()) {
 69		bytes_read = ath9k_rng_data_read(sc, rng_buf,
 70						 ATH9K_RNG_BUF_SIZE);
 71		if (unlikely(!bytes_read)) {
 72			msleep_interruptible(10);
 73			continue;
 74		}
 75
 76		/* sleep until entropy bits under write_wakeup_threshold */
 77		add_hwgenerator_randomness((void *)rng_buf, bytes_read,
 78					   ATH9K_RNG_ENTROPY(bytes_read));
 79	}
 80
 81	kfree(rng_buf);
 82out:
 83	sc->rng_task = NULL;
 84
 85	return 0;
 86}
 87
 88void ath9k_rng_start(struct ath_softc *sc)
 89{
 90	struct ath_hw *ah = sc->sc_ah;
 91
 92	if (sc->rng_task)
 93		return;
 94
 95	if (!AR_SREV_9300_20_OR_LATER(ah))
 96		return;
 97
 98	sc->rng_task = kthread_run(ath9k_rng_kthread, sc, "ath9k-hwrng");
 99	if (IS_ERR(sc->rng_task))
100		sc->rng_task = NULL;
101}
102
103void ath9k_rng_stop(struct ath_softc *sc)
104{
105	if (sc->rng_task)
106		kthread_stop(sc->rng_task);
107}