From 95bffa4b847b09a46b3c05e87d22d8a932dbad4c Mon Sep 17 00:00:00 2001
From: kettenis <kettenis@openbsd.org>
Date: Sat, 24 Feb 2018 13:46:22 +0000
Subject: [PATCH] Add bcmrng(4), a driver for the random number generator on
 the Raspberry Pi.

---
 sys/dev/fdt/bcm2835_rng.c | 114 ++++++++++++++++++++++++++++++++++++++
 sys/dev/fdt/files.fdt     |   6 +-
 2 files changed, 119 insertions(+), 1 deletion(-)
 create mode 100644 sys/dev/fdt/bcm2835_rng.c

diff --git a/sys/dev/fdt/bcm2835_rng.c b/sys/dev/fdt/bcm2835_rng.c
new file mode 100644
index 00000000000..4712e835375
--- /dev/null
+++ b/sys/dev/fdt/bcm2835_rng.c
@@ -0,0 +1,114 @@
+/*	$OpenBSD: bcm2835_rng.c,v 1.1 2018/02/24 13:46:22 kettenis Exp $	*/
+/*
+ * Copyright (c) 2018 Mark Kettenis <kettenis@openbsd.org>
+ *
+ * Permission to use, copy, modify, and 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 <sys/param.h>
+#include <sys/systm.h>
+#include <sys/device.h>
+#include <sys/timeout.h>
+
+#include <machine/bus.h>
+#include <machine/fdt.h>
+
+#include <dev/rndvar.h>
+#include <dev/ofw/openfirm.h>
+#include <dev/ofw/fdt.h>
+
+/* Registers */
+#define RNG_CTRL		0x0000
+#define  RNG_CTRL_EN		(1 << 0)
+#define RNG_STATUS		0x0004
+#define  RNG_STATUS_COUNT(x)	((x) >> 24)
+#define RNG_DATA		0x0008
+
+#define HREAD4(sc, reg)							\
+	(bus_space_read_4((sc)->sc_iot, (sc)->sc_ioh, (reg)))
+#define HWRITE4(sc, reg, val)						\
+	bus_space_write_4((sc)->sc_iot, (sc)->sc_ioh, (reg), (val))
+
+struct bcmrng_softc {
+	struct device		sc_dev;
+	bus_space_tag_t		sc_iot;
+	bus_space_handle_t	sc_ioh;
+
+	struct timeout		sc_to;
+};
+
+int	bcmrng_match(struct device *, void *, void *);
+void	bcmrng_attach(struct device *, struct device *, void *);
+
+struct cfattach	bcmrng_ca = {
+	sizeof (struct bcmrng_softc), bcmrng_match, bcmrng_attach
+};
+
+struct cfdriver bcmrng_cd = {
+	NULL, "bcmrng", DV_DULL
+};
+
+void	bcmrng_rnd(void *);
+
+int
+bcmrng_match(struct device *parent, void *match, void *aux)
+{
+	struct fdt_attach_args *faa = aux;
+
+	return OF_is_compatible(faa->fa_node, "brcm,bcm2835-rng");
+}
+
+void
+bcmrng_attach(struct device *parent, struct device *self, void *aux)
+{
+	struct bcmrng_softc *sc = (struct bcmrng_softc *)self;
+	struct fdt_attach_args *faa = aux;
+
+	if (faa->fa_nreg < 1) {
+		printf(": no registers\n");
+		return;
+	}
+
+	sc->sc_iot = faa->fa_iot;
+	if (bus_space_map(sc->sc_iot, faa->fa_reg[0].addr,
+	    faa->fa_reg[0].size, 0, &sc->sc_ioh)) {
+		printf(": can't map registers\n");
+		return;
+	}
+
+	printf("\n");
+
+	/* Discard initial numbers which may be "less" random. */
+	HWRITE4(sc, RNG_STATUS, 250000);
+	HWRITE4(sc, RNG_CTRL, RNG_CTRL_EN);
+
+	timeout_set(&sc->sc_to, bcmrng_rnd, sc);
+	bcmrng_rnd(sc);
+}
+
+void
+bcmrng_rnd(void *arg)
+{
+	struct bcmrng_softc *sc = arg;
+	uint32_t status, data;
+	int i, count;
+
+	status = HREAD4(sc, RNG_STATUS);
+	count = MIN(4, RNG_STATUS_COUNT(status));
+	for (i = 0; i < count; i++) {
+		data = HREAD4(sc, RNG_DATA);
+		add_true_randomness(data);
+	}
+
+	timeout_add_sec(&sc->sc_to, 1);
+}
diff --git a/sys/dev/fdt/files.fdt b/sys/dev/fdt/files.fdt
index 5ab9386670f..e17ff35fad9 100644
--- a/sys/dev/fdt/files.fdt
+++ b/sys/dev/fdt/files.fdt
@@ -1,4 +1,4 @@
-#	$OpenBSD: files.fdt,v 1.39 2018/02/24 13:23:21 kettenis Exp $
+#	$OpenBSD: files.fdt,v 1.40 2018/02/24 13:46:22 kettenis Exp $
 #
 # Config file and device description for machine-independent FDT code.
 # Included by ports that need it.
@@ -57,6 +57,10 @@ device	bcmdog
 attach	bcmdog at fdt
 file	dev/fdt/bcm2835_dog.c		bcmdog
 
+device	bcmrng
+attach	bcmrng at fdt
+file	dev/fdt/bcm2835_rng.c		bcmrng
+
 device	bcmtemp
 attach	bcmtemp at fdt
 file	dev/fdt/bcm2835_temp.c		bcmtemp
-- 
2.20.1