linux-kernel - [PATCH v2] ath9k: use hw_random API instead of directly dumping into random.c

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Date:   Wed, 16 Feb 2022 01:02:30 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     miaoqing@...eaurora.org, rsalvaterra@...il.com,
        Toke Høiland-Jørgensen <toke@...e.dk>,
        "Sepehrdad, Pouyan" <pouyans@....qualcomm.com>,
        ath9k-devel <ath9k-devel@....qualcomm.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        Kalle Valo <kvalo@...nel.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: [PATCH v2] ath9k: use hw_random API instead of directly dumping into random.c

Hardware random number generators are supposed to use the hw_random
framework. This commit turns ath9k's kthread-based design into a proper
hw_random driver.

This compiles, but I have no hardware or other ability to determine
whether it works. I'll leave further development up to the ath9k
and hw_random maintainers.

Cc: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: Kalle Valo <kvalo@...nel.org>
Cc: Dominik Brodowski <linux@...inikbrodowski.net>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
v2 operates on whole words when possible.

 drivers/net/wireless/ath/ath9k/ath9k.h |  2 +-
 drivers/net/wireless/ath/ath9k/rng.c   | 72 +++++++++++---------------
 2 files changed, 30 insertions(+), 44 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index ef6f5ea06c1f..142f472903dc 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -1072,7 +1072,7 @@ struct ath_softc {
 
 #ifdef CONFIG_ATH9K_HWRNG
 	u32 rng_last;
-	struct task_struct *rng_task;
+	struct hwrng rng_ops;
 #endif
 };
 
diff --git a/drivers/net/wireless/ath/ath9k/rng.c b/drivers/net/wireless/ath/ath9k/rng.c
index aae2bd3cac69..a0a58f8e08d3 100644
--- a/drivers/net/wireless/ath/ath9k/rng.c
+++ b/drivers/net/wireless/ath/ath9k/rng.c
@@ -22,11 +22,6 @@
 #include "hw.h"
 #include "ar9003_phy.h"
 
-#define ATH9K_RNG_BUF_SIZE	320
-#define ATH9K_RNG_ENTROPY(x)	(((x) * 8 * 10) >> 5) /* quality: 10/32 */
-
-static DECLARE_WAIT_QUEUE_HEAD(rng_queue);
-
 static int ath9k_rng_data_read(struct ath_softc *sc, u32 *buf, u32 buf_size)
 {
 	int i, j;
@@ -72,61 +67,52 @@ static u32 ath9k_rng_delay_get(u32 fail_stats)
 	return delay;
 }
 
-static int ath9k_rng_kthread(void *data)
+static int ath9k_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
 {
-	int bytes_read;
-	struct ath_softc *sc = data;
-	u32 *rng_buf;
-	u32 delay, fail_stats = 0;
-
-	rng_buf = kmalloc_array(ATH9K_RNG_BUF_SIZE, sizeof(u32), GFP_KERNEL);
-	if (!rng_buf)
-		goto out;
-
-	while (!kthread_should_stop()) {
-		bytes_read = ath9k_rng_data_read(sc, rng_buf,
-						 ATH9K_RNG_BUF_SIZE);
-		if (unlikely(!bytes_read)) {
-			delay = ath9k_rng_delay_get(++fail_stats);
-			wait_event_interruptible_timeout(rng_queue,
-							 kthread_should_stop(),
-							 msecs_to_jiffies(delay));
-			continue;
-		}
-
-		fail_stats = 0;
-
-		/* sleep until entropy bits under write_wakeup_threshold */
-		add_hwgenerator_randomness((void *)rng_buf, bytes_read,
-					   ATH9K_RNG_ENTROPY(bytes_read));
+	struct ath_softc *sc = container_of(rng, struct ath_softc, rng_ops);
+	int bytes_read = 0;
+	u32 fail_stats = 0, word;
+
+retry:
+	if (max & ~3UL)
+		bytes_read = ath9k_rng_data_read(sc, buf, max >> 2);
+	if ((max & 3UL) && ath9k_rng_data_read(sc, &word, 1)) {
+		memcpy(buf + bytes_read, &word, max & 3);
+		bytes_read += max & 3;
+		memzero_explicit(&word, sizeof(word));
+	}
+	if (max && unlikely(!bytes_read) && wait) {
+		msleep(ath9k_rng_delay_get(++fail_stats));
+		goto retry;
 	}
 
-	kfree(rng_buf);
-out:
-	sc->rng_task = NULL;
-
-	return 0;
+	return bytes_read;
 }
 
 void ath9k_rng_start(struct ath_softc *sc)
 {
 	struct ath_hw *ah = sc->sc_ah;
+	int ret;
 
-	if (sc->rng_task)
+	if (sc->rng_ops.read)
 		return;
 
 	if (!AR_SREV_9300_20_OR_LATER(ah))
 		return;
 
-	sc->rng_task = kthread_run(ath9k_rng_kthread, sc, "ath9k-hwrng");
-	if (IS_ERR(sc->rng_task))
-		sc->rng_task = NULL;
+	sc->rng_ops.name = "ath9k";
+	sc->rng_ops.read = ath9k_rng_read;
+	sc->rng_ops.quality = 320;
+
+	ret = devm_hwrng_register(sc->dev, &sc->rng_ops);
+	if (ret)
+		sc->rng_ops.read = NULL;
 }
 
 void ath9k_rng_stop(struct ath_softc *sc)
 {
-	if (sc->rng_task) {
-		kthread_stop(sc->rng_task);
-		sc->rng_task = NULL;
+	if (sc->rng_ops.read) {
+		devm_hwrng_unregister(sc->dev, &sc->rng_ops);
+		sc->rng_ops.read = NULL;
 	}
 }
-- 
2.35.0