ath9k: export HW random number generator

We measured the FFT-based entropy in 3 ways, Shannon entropy,
collision entropy, and directly measured min-entropy. Just to
be conservative, we recommend the estimated min-Entropy to be
10 bits per 16-bit value.

Analysis was done by Jacobson,David([e-mail]).

Signed-off-by: Miaoqing Pan <[e-mail]>
Signed-off-by: Kalle Valo <[e-mail]>

drivers/net/wireless/ath/ath9k/Kconfig

···
 	depends on ATH9K_HTC && DEBUG_FS
 	---help---
 	  Say Y, if you need access to ath9k_htc's statistics.
+
+config ATH9K_HWRNG
+	bool "Random number generator support"
+	depends on ATH9K && (HW_RANDOM = y || HW_RANDOM = ATH9K)
+	default y
+	---help---
+	  Provides a hardware random number generator to the kernel.

drivers/net/wireless/ath/ath9k/Makefile

···
 ath9k-$(CONFIG_ATH9K_DFS_CERTIFIED) += dfs.o
 ath9k-$(CONFIG_ATH9K_TX99) += tx99.o
 ath9k-$(CONFIG_ATH9K_WOW) += wow.o
+ath9k-$(CONFIG_ATH9K_HWRNG) += rng.o
 
 ath9k-$(CONFIG_ATH9K_DEBUGFS) += debug.o
 

drivers/net/wireless/ath/ath9k/ath9k.h

···
 #include <linux/leds.h>
 #include <linux/completion.h>
 #include <linux/time.h>
+#include <linux/hw_random.h>
 
 #include "common.h"
 #include "debug.h"
···
 	u32 wow_intr_before_sleep;
 	bool force_wow;
 #endif
+
+#ifdef CONFIG_ATH9K_HWRNG
+	struct hwrng rng;
+	bool rng_initialized;
+	u32 rng_last;
+#endif
 };
 
 /********/
···
 	return 0;
 }
 #endif /* CONFIG_ATH9K_TX99 */
+
+/***************************/
+/* Random Number Generator */
+/***************************/
+#ifdef CONFIG_ATH9K_HWRNG
+void ath9k_rng_register(struct ath_softc *sc);
+void ath9k_rng_unregister(struct ath_softc *sc);
+#else
+static inline void ath9k_rng_register(struct ath_softc *sc)
+{
+}
+
+static inline void ath9k_rng_unregister(struct ath_softc *sc)
+{
+}
+#endif
 
 static inline void ath_read_cachesize(struct ath_common *common, int *csz)
 {

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

···
 
 	ath9k_ps_restore(sc);
 
+	ath9k_rng_register(sc);
+
 	return 0;
 }
 
···
 	bool prev_idle;
 
 	ath9k_deinit_channel_context(sc);
+
+	ath9k_rng_unregister(sc);
 
 	mutex_lock(&sc->mutex);
 

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

···
+/*
+ * Copyright (c) 2015 Qualcomm Atheros, Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "ath9k.h"
+#include "hw.h"
+#include "ar9003_phy.h"
+
+static int ath9k_rng_data_read(struct hwrng *rng, u32 *data)
+{
+	u32 v1, v2;
+	struct ath_softc *sc = (struct ath_softc *)rng->priv;
+	struct ath_hw *ah = sc->sc_ah;
+
+	ath9k_ps_wakeup(sc);
+
+	REG_RMW_FIELD(ah, AR_PHY_TEST, AR_PHY_TEST_BBB_OBS_SEL, 5);
+	REG_CLR_BIT(ah, AR_PHY_TEST, AR_PHY_TEST_RX_OBS_SEL_BIT5);
+	REG_RMW_FIELD(ah, AR_PHY_TEST_CTL_STATUS, AR_PHY_TEST_CTL_RX_OBS_SEL, 0);
+
+	v1 = REG_READ(ah, AR_PHY_TST_ADC);
+	v2 = REG_READ(ah, AR_PHY_TST_ADC);
+
+	ath9k_ps_restore(sc);
+
+	/* wait for data ready */
+	if (v1 && v2 && sc->rng_last != v1 && v1 != v2) {
+		*data = (v1 & 0xffff) | (v2 << 16);
+		sc->rng_last = v2;
+
+		return sizeof(u32);
+	}
+
+	sc->rng_last = v2;
+
+	return 0;
+}
+
+void ath9k_rng_register(struct ath_softc *sc)
+{
+	struct ath_hw *ah = sc->sc_ah;
+
+	if (WARN_ON(sc->rng_initialized))
+		return;
+
+	if (!AR_SREV_9300_20_OR_LATER(ah))
+		return;
+
+	sc->rng.name = "ath9k";
+	sc->rng.data_read = ath9k_rng_data_read;
+	sc->rng.priv = (unsigned long)sc;
+
+	if (!hwrng_register(&sc->rng))
+		sc->rng_initialized = true;
+}
+
+void ath9k_rng_unregister(struct ath_softc *sc)
+{
+	if (sc->rng_initialized) {
+		hwrng_unregister(&sc->rng);
+		sc->rng_initialized = false;
+	}
+}