[PATCH 11/12] can: rx-fifo: Add support for simple irq offloading

[Marc Kleine-Budde <mkl@pengutronix.de>]

From: David Jander <david@protonic.nl>

Some CAN controllers have a usable FIFO already but can still benefit from
off-loading the CAN controller FIFO. The mailboxes of the FIFO  are copied to a
ring buffer during the interrupt and then transmitted in a NAPI context.

Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/Makefile    |   3 +-
 drivers/net/can/rx-fifo.c   | 180 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/can/rx-fifo.h |  58 ++++++++++++++
 3 files changed, 240 insertions(+), 1 deletion(-)
 create mode 100644 drivers/net/can/rx-fifo.c
 create mode 100644 include/linux/can/rx-fifo.h

diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile
index c533c62b0f5e..8b3f6e96e4ba 100644
--- a/drivers/net/can/Makefile
+++ b/drivers/net/can/Makefile
@@ -6,7 +6,8 @@ obj-$(CONFIG_CAN_VCAN)		+= vcan.o
 obj-$(CONFIG_CAN_SLCAN)		+= slcan.o
 
 obj-$(CONFIG_CAN_DEV)		+= can-dev.o
-can-dev-y			:= dev.o
+can-dev-y			+= dev.o
+can-dev-y			+= rx-fifo.o
 
 can-dev-$(CONFIG_CAN_LEDS)	+= led.o
 
diff --git a/drivers/net/can/rx-fifo.c b/drivers/net/can/rx-fifo.c
new file mode 100644
index 000000000000..2a0fb37f1bbb
--- /dev/null
+++ b/drivers/net/can/rx-fifo.c
@@ -0,0 +1,180 @@
+/*
+ * Copyright (c) 2014 David Jander, Protonic Holland
+ * Copyright (C) 2014, 2015 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the version 2 of the GNU General Public License
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/circ_buf.h>
+#include <linux/can/dev.h>
+#include <linux/can/rx-fifo.h>
+
+static int can_rx_fifo_napi_read_frame(struct can_rx_fifo *fifo, int index)
+{
+	struct net_device *dev = fifo->dev;
+	struct net_device_stats *stats = &dev->stats;
+	struct sk_buff *skb;
+	struct can_frame *cf;
+
+	skb = alloc_can_skb(dev, &cf);
+	if (unlikely(!skb)) {
+		stats->rx_dropped++;
+		return 0;
+	}
+
+	memcpy(cf, &fifo->ring[index], sizeof(*cf));
+	memset(&fifo->ring[index], 0x0, sizeof(*cf));
+
+	stats->rx_packets++;
+	stats->rx_bytes += cf->can_dlc;
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
+static int can_rx_fifo_napi_poll(struct napi_struct *napi, int quota)
+{
+	struct can_rx_fifo *fifo = container_of(napi, struct can_rx_fifo, napi);
+	unsigned int tail;
+	int work_done = 0;
+
+	if (fifo->poll_pre_read && work_done < quota)
+		work_done += fifo->poll_pre_read(fifo);
+
+	/* handle mailboxes */
+	tail = fifo->ring_tail;
+	while ((CIRC_CNT(smp_load_acquire(&fifo->ring_head), tail, fifo->ring_size)) &&
+	       (work_done < quota)) {
+		work_done += can_rx_fifo_napi_read_frame(fifo, tail);
+		tail++;
+		tail &= fifo->ring_size -1;
+		smp_store_release(&fifo->ring_tail, tail);
+	}
+
+	if (fifo->poll_post_read && work_done < quota)
+		work_done += fifo->poll_post_read(fifo);
+
+	if (work_done < quota) {
+		unsigned int head;
+
+		napi_complete(napi);
+
+		/* Check if there was another interrupt */
+		head = smp_load_acquire(&fifo->ring_head);
+		if (((CIRC_CNT(head, tail, fifo->ring_size)) || fifo->poll_errors) &&
+		    napi_reschedule(&fifo->napi)) {
+			fifo->poll_errors = false;
+		}
+
+		if (fifo->poll_error_interrupts_enable)
+			fifo->poll_error_interrupts_enable(fifo);
+	}
+
+	can_led_event(fifo->dev, CAN_LED_EVENT_RX);
+
+	return work_done;
+}
+
+static unsigned int can_rx_fifo_offload_one(struct can_rx_fifo *fifo, unsigned int n)
+{
+	unsigned int head, tail;
+	unsigned int ret;
+
+	head = fifo->ring_head;
+	tail = ACCESS_ONCE(fifo->ring_tail);
+	if (CIRC_SPACE(head, tail, fifo->ring_size)) {
+		ret = fifo->mailbox_read(fifo, &fifo->ring[head], n);
+		if (ret) {
+			head++;
+			head &= fifo->ring_size - 1;
+			smp_store_release(&fifo->ring_head, head);
+		}
+	} else {
+		/* Circular buffer is fill, read to discard mailbox */
+		ret = fifo->mailbox_read(fifo, &fifo->overflow, n);
+		if (ret)
+			fifo->dev->stats.rx_dropped++;
+	}
+
+	return ret;
+}
+
+int can_rx_fifo_irq_offload_simple(struct can_rx_fifo *fifo)
+{
+	unsigned int received = 0;
+	unsigned int ret;
+
+	do {
+		ret = can_rx_fifo_offload_one(fifo, 0);
+		received += ret;
+	} while (ret);
+
+	if (received)
+		can_rx_fifo_schedule(fifo);
+
+	return received;
+}
+EXPORT_SYMBOL_GPL(can_rx_fifo_irq_offload_simple);
+
+static int can_rx_fifo_init_ring(struct net_device *dev,
+				 struct can_rx_fifo *fifo, unsigned int weight)
+{
+	fifo->dev = dev;
+
+	/* Make ring-buffer a sensible size that is a power of 2 */
+	fifo->ring_size = 2 << fls(weight);
+	fifo->ring = kzalloc(sizeof(struct can_frame) * fifo->ring_size,
+			     GFP_KERNEL);
+	if (!fifo->ring)
+		return -ENOMEM;
+
+	fifo->ring_head = fifo->ring_tail = 0;
+	netif_napi_add(dev, &fifo->napi, can_rx_fifo_napi_poll, weight);
+
+	return 0;
+}
+
+int can_rx_fifo_add_simple(struct net_device *dev, struct can_rx_fifo *fifo, unsigned int weight)
+{
+	int ret;
+
+	if (!fifo->mailbox_read)
+		return -EINVAL;
+
+	ret = can_rx_fifo_init_ring(dev, fifo, weight);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(can_rx_fifo_add_simple);
+
+void can_rx_fifo_enable(struct can_rx_fifo *fifo)
+{
+	napi_enable(&fifo->napi);
+}
+EXPORT_SYMBOL_GPL(can_rx_fifo_enable);
+
+void can_rx_fifo_irq_error(struct can_rx_fifo *fifo)
+{
+	fifo->poll_errors = true;
+	can_rx_fifo_schedule(fifo);
+}
+EXPORT_SYMBOL_GPL(can_rx_fifo_irq_error);
+
+void can_rx_fifo_del(struct can_rx_fifo *fifo)
+{
+	netif_napi_del(&fifo->napi);
+	kfree(fifo->ring);
+}
+EXPORT_SYMBOL_GPL(can_rx_fifo_del);
diff --git a/include/linux/can/rx-fifo.h b/include/linux/can/rx-fifo.h
new file mode 100644
index 000000000000..fc157f23722c
--- /dev/null
+++ b/include/linux/can/rx-fifo.h
@@ -0,0 +1,58 @@
+/*
+ * linux/can/rx-fifo.h
+ *
+ * Copyright (c) 2014 David Jander, Protonic Holland
+ * Copyright (c) 2014, 2015 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the version 2 of the GNU General Public License
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _CAN_RX_FIFO_H
+#define _CAN_RX_FIFO_H
+
+#include <linux/netdevice.h>
+#include <linux/can.h>
+
+struct can_rx_fifo {
+	struct net_device *dev;
+
+	void (*poll_error_interrupts_enable)(struct can_rx_fifo *fifo);
+	unsigned int (*mailbox_read)(struct can_rx_fifo *fifo, struct can_frame *cf, unsigned int mb);
+	unsigned int (*poll_pre_read)(struct can_rx_fifo *fifo);
+	unsigned int (*poll_post_read)(struct can_rx_fifo *fifo);
+
+	unsigned int ring_size;
+	unsigned int ring_head;
+	unsigned int ring_tail;
+
+	struct can_frame *ring;
+	struct can_frame overflow;
+	struct napi_struct napi;
+
+	bool poll_errors;
+};
+
+int can_rx_fifo_add_simple(struct net_device *dev, struct can_rx_fifo *fifo, unsigned int weight);
+int can_rx_fifo_irq_offload_simple(struct can_rx_fifo *fifo);
+void can_rx_fifo_irq_error(struct can_rx_fifo *fifo);
+void can_rx_fifo_del(struct can_rx_fifo *fifo);
+void can_rx_fifo_enable(struct can_rx_fifo *fifo);
+
+static inline void can_rx_fifo_schedule(struct can_rx_fifo *fifo)
+{
+	napi_schedule(&fifo->napi);
+}
+
+static inline void can_rx_fifo_disable(struct can_rx_fifo *fifo)
+{
+	napi_disable(&fifo->napi);
+}
+
+#endif /* !_CAN_RX_FIFO_H */
-- 
2.5.0