scmi: Add an SCMI VirtIO transport driver

Add an SCMI transport driver based on the virtio-scmi backend.

Reviewed by:	andrew, bryanv
Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D43048

sys/conf/files.arm64

@@ -275,6 +275,7 @@ dev/firmware/arm/scmi_clk.c			optional fdt scmi
 dev/firmware/arm/scmi_if.m			optional fdt scmi
 dev/firmware/arm/scmi_mailbox.c			optional fdt scmi
 dev/firmware/arm/scmi_smc.c			optional fdt scmi
+dev/firmware/arm/scmi_virtio.c			optional fdt scmi
 dev/firmware/arm/scmi_shmem.c			optional fdt scmi
 
 dev/gpio/pl061.c				optional pl061 gpio

sys/dev/firmware/arm/scmi.c

@@ -484,10 +484,19 @@ scmi_process_response(struct scmi_softc *sc, uint32_t hdr)
 
 	mtx_lock_spin(&req->mtx);
 	req->done = true;
-	if (!req->timed_out)
-		wakeup(req);
-	else
+	if (!req->timed_out) {
+		/*
+		 * Consider the case in which a polled message is picked
+		 * by chance on the IRQ path on another CPU: setting poll_done
+		 * will terminate the other poll loop.
+		 */
+		if (!req->msg.polling)
+			wakeup(req);
+		else
+			atomic_store_rel_int(&req->msg.poll_done, 1);
+	} else {
 		timed_out = true;
+	}
 	mtx_unlock_spin(&req->mtx);
 
 	if (timed_out)

sys/dev/firmware/arm/scmi.h

@@ -62,12 +62,14 @@ struct scmi_softc {
 
 struct scmi_msg {
 	bool		polling;
+	int		poll_done;
 	uint32_t	tx_len;
 	uint32_t	rx_len;
 #define SCMI_MSG_HDR_SIZE	(sizeof(uint32_t))
 	uint32_t	hdr;
 	uint8_t		payld[];
 };
+#define hdr_to_msg(h)	__containerof((h), struct scmi_msg, hdr)
 
 void *scmi_buf_get(device_t dev, uint8_t protocol_id, uint8_t message_id,
 		   int tx_payd_sz, int rx_payld_sz);

sys/dev/firmware/arm/scmi_virtio.c

@@ -0,0 +1,298 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2023 Arm Ltd
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/bus.h>
+#include <sys/cpu.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
+
+#include <dev/fdt/simplebus.h>
+#include <dev/fdt/fdt_common.h>
+#include <dev/ofw/ofw_bus_subr.h>
+
+#include <dev/virtio/scmi/virtio_scmi.h>
+
+#include "scmi.h"
+#include "scmi_protocols.h"
+
+#define SCMI_VIRTIO_POLLING_INTERVAL_MS	2
+
+struct scmi_virtio_softc {
+	struct scmi_softc	base;
+	device_t		virtio_dev;
+	int			cmdq_sz;
+	int			evtq_sz;
+	void			*p2a_pool;
+};
+
+static void	scmi_virtio_callback(void *, unsigned int, void *);
+static void	*scmi_virtio_p2a_pool_init(device_t, unsigned int);
+static int	scmi_virtio_transport_init(device_t);
+static void	scmi_virtio_transport_cleanup(device_t);
+static int	scmi_virtio_xfer_msg(device_t, struct scmi_msg *);
+static int	scmi_virtio_poll_msg(device_t, struct scmi_msg *, unsigned int);
+static void	scmi_virtio_clear_channel(device_t, void *);
+static int	scmi_virtio_probe(device_t);
+static int	scmi_virtio_attach(device_t);
+
+static void
+scmi_virtio_callback(void *msg, unsigned int len, void *priv)
+{
+	struct scmi_virtio_softc *sc;
+	uint32_t hdr;
+
+	sc = priv;
+
+	if (msg == NULL || len < sizeof(hdr)) {
+		device_printf(sc->virtio_dev, "Ignoring malformed message.\n");
+		return;
+	}
+
+	hdr = le32toh(*((uint32_t *)msg));
+	scmi_rx_irq_callback(sc->base.dev, msg, hdr);
+}
+
+static void *
+scmi_virtio_p2a_pool_init(device_t dev, unsigned int max_msg)
+{
+	struct scmi_virtio_softc *sc;
+	void *pool;
+	uint8_t *buf;
+	int i;
+
+	sc = device_get_softc(dev);
+
+	pool = mallocarray(max_msg, SCMI_MAX_MSG_SIZE, M_DEVBUF,
+	    M_ZERO | M_WAITOK);
+
+	for (i = 0, buf = pool; i < max_msg; i++, buf += SCMI_MAX_MSG_SIZE) {
+		/* Feed platform with pre-allocated P2A buffers */
+		virtio_scmi_message_enqueue(sc->virtio_dev,
+		    VIRTIO_SCMI_CHAN_P2A, buf, 0, SCMI_MAX_MSG_SIZE);
+	}
+
+	device_printf(dev,
+	    "Fed %d initial P2A buffers to platform.\n", max_msg);
+
+	return (pool);
+}
+
+static void
+scmi_virtio_clear_channel(device_t dev, void *msg)
+{
+	struct scmi_virtio_softc *sc;
+
+	sc = device_get_softc(dev);
+	virtio_scmi_message_enqueue(sc->virtio_dev, VIRTIO_SCMI_CHAN_P2A,
+	    msg, 0, SCMI_MAX_MSG_SIZE);
+}
+
+static int
+scmi_virtio_transport_init(device_t dev)
+{
+	struct scmi_virtio_softc *sc;
+	int ret;
+
+	sc = device_get_softc(dev);
+
+	sc->cmdq_sz = virtio_scmi_channel_size_get(sc->virtio_dev,
+	    VIRTIO_SCMI_CHAN_A2P);
+	sc->evtq_sz = virtio_scmi_channel_size_get(sc->virtio_dev,
+	    VIRTIO_SCMI_CHAN_P2A);
+
+	if (!sc->cmdq_sz) {
+		device_printf(dev,
+		    "VirtIO cmdq virtqueue not found. Aborting.\n");
+		return (ENXIO);
+	}
+
+	/*
+	 * P2A buffers are owned by the platform initially; allocate a feed an
+	 * appropriate number of buffers.
+	 */
+	if (sc->evtq_sz != 0) {
+		sc->p2a_pool = scmi_virtio_p2a_pool_init(dev, sc->evtq_sz);
+		if (sc->p2a_pool == NULL)
+			return (ENOMEM);
+	}
+
+	/* Note that setting a callback also enables that VQ interrupts */
+	ret = virtio_scmi_channel_callback_set(sc->virtio_dev,
+	    VIRTIO_SCMI_CHAN_A2P, scmi_virtio_callback, sc);
+	if (ret) {
+		device_printf(dev, "Failed to set VirtIO cmdq callback.\n");
+		return (ENXIO);
+	}
+
+	device_printf(dev,
+	    "VirtIO cmdq virtqueue configured - cmdq_sz:%d\n", sc->cmdq_sz);
+
+	/* P2A channel is optional */
+	if (sc->evtq_sz) {
+		ret = virtio_scmi_channel_callback_set(sc->virtio_dev,
+		    VIRTIO_SCMI_CHAN_P2A, scmi_virtio_callback, sc);
+		if (ret == 0) {
+			device_printf(dev,
+			    "VirtIO evtq virtqueue configured - evtq_sz:%d\n",
+			    sc->evtq_sz);
+		} else {
+			device_printf(dev,
+			    "Failed to set VirtIO evtq callback.Skip.\n");
+			sc->evtq_sz = 0;
+		}
+	}
+
+	sc->base.trs_desc.reply_timo_ms = 100;
+
+	return (0);
+}
+
+static void
+scmi_virtio_transport_cleanup(device_t dev)
+{
+	struct scmi_virtio_softc *sc;
+
+	sc = device_get_softc(dev);
+
+	if (sc->evtq_sz != 0) {
+		virtio_scmi_channel_callback_set(sc->virtio_dev,
+		    VIRTIO_SCMI_CHAN_P2A, NULL, NULL);
+		free(sc->p2a_pool, M_DEVBUF);
+	}
+
+	virtio_scmi_channel_callback_set(sc->virtio_dev,
+	    VIRTIO_SCMI_CHAN_A2P, NULL, NULL);
+}
+
+static int
+scmi_virtio_xfer_msg(device_t dev, struct scmi_msg *msg)
+{
+	struct scmi_virtio_softc *sc;
+
+	sc = device_get_softc(dev);
+
+	return (virtio_scmi_message_enqueue(sc->virtio_dev,
+	    VIRTIO_SCMI_CHAN_A2P, &msg->hdr, msg->tx_len, msg->rx_len));
+}
+
+static int
+scmi_virtio_poll_msg(device_t dev, struct scmi_msg *msg, unsigned int tmo_ms)
+{
+	struct scmi_virtio_softc *sc;
+	device_t vdev;
+	int tmo_loops;
+
+	sc = device_get_softc(dev);
+	vdev = sc->virtio_dev;
+
+	tmo_loops = tmo_ms / SCMI_VIRTIO_POLLING_INTERVAL_MS;
+	while (tmo_loops-- && atomic_load_acq_int(&msg->poll_done) == 0) {
+		struct scmi_msg *rx_msg;
+		void *rx_buf;
+		uint32_t rx_len;
+
+		rx_buf = virtio_scmi_message_poll(vdev, &rx_len);
+		if (rx_buf == NULL) {
+			DELAY(SCMI_VIRTIO_POLLING_INTERVAL_MS * 1000);
+			continue;
+		}
+
+		rx_msg = hdr_to_msg(rx_buf);
+		rx_msg->rx_len = rx_len;
+		/* Complete the polling on any poll path */
+		if (rx_msg->polling)
+			atomic_store_rel_int(&rx_msg->poll_done, 1);
+
+		if (__predict_true(rx_msg == msg))
+			break;
+
+		/*
+		 * Polling returned an unexpected message: either a message
+		 * polled by some other thread of execution or a message not
+		 * supposed to be polled.
+		 */
+		device_printf(dev, "POLLED OoO HDR:|%08X| - polling:%d\n",
+		    rx_msg->hdr, rx_msg->polling);
+
+		if (!rx_msg->polling)
+			scmi_rx_irq_callback(sc->base.dev, rx_msg, rx_msg->hdr);
+	}
+
+	return (tmo_loops > 0 ? 0 : ETIMEDOUT);
+}
+
+static int
+scmi_virtio_probe(device_t dev)
+{
+	if (!ofw_bus_is_compatible(dev, "arm,scmi-virtio"))
+		return (ENXIO);
+
+	if (!ofw_bus_status_okay(dev))
+		return (ENXIO);
+
+	device_set_desc(dev, "ARM SCMI VirtIO Transport driver");
+
+	return (BUS_PROBE_DEFAULT);
+}
+
+static int
+scmi_virtio_attach(device_t dev)
+{
+	struct scmi_virtio_softc *sc;
+
+	sc = device_get_softc(dev);
+	sc->virtio_dev = virtio_scmi_transport_get();
+	if (sc->virtio_dev == NULL)
+		return (1);
+
+	/* When attach fails there is nothing to cleanup*/
+	return (scmi_attach(dev));
+}
+
+static device_method_t scmi_virtio_methods[] = {
+	DEVMETHOD(device_probe,		scmi_virtio_probe),
+	DEVMETHOD(device_attach,	scmi_virtio_attach),
+
+	/* SCMI interface */
+	DEVMETHOD(scmi_transport_init,		scmi_virtio_transport_init),
+	DEVMETHOD(scmi_transport_cleanup,	scmi_virtio_transport_cleanup),
+	DEVMETHOD(scmi_xfer_msg,		scmi_virtio_xfer_msg),
+	DEVMETHOD(scmi_poll_msg,		scmi_virtio_poll_msg),
+	DEVMETHOD(scmi_clear_channel,		scmi_virtio_clear_channel),
+
+	DEVMETHOD_END
+};
+
+DEFINE_CLASS_1(scmi_virtio, scmi_virtio_driver, scmi_virtio_methods,
+    sizeof(struct scmi_virtio_softc), scmi_driver);
+
+/* Needs to be after the mmio_sram driver */
+DRIVER_MODULE(scmi_virtio, simplebus, scmi_virtio_driver, 0, 0);
+MODULE_VERSION(scmi_virtio, 1);