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can: gs_usb: convert to NAPI/rx-offload to avoid OoO reception
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The driver used to pass received CAN frames/skbs to the network stack
with netif_rx(). In netif_rx() the skbs are queued to the local CPU.
If IRQs are handled in round robin, OoO packets may occur.

To avoid out-of-order reception convert the driver from netif_rx() to
NAPI.

For USB devices with timestamping support use the rx-offload helper
can_rx_offload_queue_timestamp() for the RX, and
can_rx_offload_get_echo_skb_queue_timestamp() for the TX path. Devices
without timestamping support use can_rx_offload_queue_tail() for RX,
and can_rx_offload_get_echo_skb_queue_tail() for the TX path.

Link: https://lore.kernel.org/all/[email protected]
Link: candle-usb/candleLight_fw#166
Link: https://lore.kernel.org/all/[email protected]
Signed-off-by: Marc Kleine-Budde <[email protected]>
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@marckleinebudde
marckleinebudde committed Jul 28, 2023
1 parent 8e0e295 commit 24bc41b
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Showing 2 changed files with 67 additions and 19 deletions.
1 change: 1 addition & 0 deletions drivers/net/can/usb/Kconfig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,7 @@ config CAN_F81604

config CAN_GS_USB
tristate "Geschwister Schneider UG and candleLight compatible interfaces"
select CAN_RX_OFFLOAD
help
This driver supports the Geschwister Schneider and
bytewerk.org candleLight compatible
Expand Down
85 changes: 66 additions & 19 deletions drivers/net/can/usb/gs_usb.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
* Copyright (C) 2013-2016 Geschwister Schneider Technologie-,
* Entwicklungs- und Vertriebs UG (Haftungsbeschränkt).
* Copyright (C) 2016 Hubert Denkmair
* Copyright (c) 2023 Pengutronix, Marc Kleine-Budde <[email protected]>
*
* Many thanks to all socketcan devs!
*/
Expand All @@ -24,6 +25,7 @@
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/can/rx-offload.h>

/* Device specific constants */
#define USB_GS_USB_1_VENDOR_ID 0x1d50
Expand Down Expand Up @@ -282,6 +284,8 @@ struct gs_host_frame {
#define GS_MAX_TX_URBS 10
/* Only launch a max of GS_MAX_RX_URBS usb requests at a time. */
#define GS_MAX_RX_URBS 30
#define GS_NAPI_WEIGHT 32

/* Maximum number of interfaces the driver supports per device.
* Current hardware only supports 3 interfaces. The future may vary.
*/
Expand All @@ -295,6 +299,7 @@ struct gs_tx_context {
struct gs_can {
struct can_priv can; /* must be the first member */

struct can_rx_offload offload;
struct gs_usb *parent;

struct net_device *netdev;
Expand Down Expand Up @@ -506,20 +511,59 @@ static void gs_update_state(struct gs_can *dev, struct can_frame *cf)
}
}

static void gs_usb_set_timestamp(struct gs_can *dev, struct sk_buff *skb,
const struct gs_host_frame *hf)
static u32 gs_usb_set_timestamp(struct gs_can *dev, struct sk_buff *skb,
const struct gs_host_frame *hf)
{
u32 timestamp;

if (!(dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP))
return;

if (hf->flags & GS_CAN_FLAG_FD)
timestamp = le32_to_cpu(hf->canfd_ts->timestamp_us);
else
timestamp = le32_to_cpu(hf->classic_can_ts->timestamp_us);

gs_usb_skb_set_timestamp(dev, skb, timestamp);
if (skb)
gs_usb_skb_set_timestamp(dev, skb, timestamp);

return timestamp;
}

static void gs_usb_rx_offload(struct gs_can *dev, struct sk_buff *skb,
const struct gs_host_frame *hf)
{
struct can_rx_offload *offload = &dev->offload;
int rc;

if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) {
const u32 ts = gs_usb_set_timestamp(dev, skb, hf);

rc = can_rx_offload_queue_timestamp(offload, skb, ts);
} else {
rc = can_rx_offload_queue_tail(offload, skb);
}

if (rc)
dev->netdev->stats.rx_fifo_errors++;
}

static unsigned int
gs_usb_get_echo_skb(struct gs_can *dev, struct sk_buff *skb,
const struct gs_host_frame *hf)
{
struct can_rx_offload *offload = &dev->offload;
const u32 echo_id = hf->echo_id;
unsigned int len;

if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) {
const u32 ts = gs_usb_set_timestamp(dev, skb, hf);

len = can_rx_offload_get_echo_skb_queue_timestamp(offload, echo_id,
ts, NULL);
} else {
len = can_rx_offload_get_echo_skb_queue_tail(offload, echo_id,
NULL);
}

return len;
}

static void gs_usb_receive_bulk_callback(struct urb *urb)
Expand Down Expand Up @@ -592,12 +636,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
gs_update_state(dev, cf);
}

gs_usb_set_timestamp(dev, skb, hf);

stats->rx_packets++;
stats->rx_bytes += hf->can_dlc;

netif_rx(skb);
gs_usb_rx_offload(dev, skb, hf);
} else { /* echo_id == hf->echo_id */
if (hf->echo_id >= GS_MAX_TX_URBS) {
netdev_err(netdev,
Expand All @@ -617,12 +656,8 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
}

skb = dev->can.echo_skb[hf->echo_id];
gs_usb_set_timestamp(dev, skb, hf);

stats->tx_packets++;
stats->tx_bytes += can_get_echo_skb(netdev, hf->echo_id,
NULL);

stats->tx_bytes += gs_usb_get_echo_skb(dev, skb, hf);
gs_free_tx_context(txc);

atomic_dec(&dev->active_tx_urbs);
Expand All @@ -641,9 +676,12 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
cf->can_id |= CAN_ERR_CRTL;
cf->len = CAN_ERR_DLC;
cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
netif_rx(skb);

gs_usb_rx_offload(dev, skb, hf);
}

can_rx_offload_irq_finish(&dev->offload);

resubmit_urb:
usb_fill_bulk_urb(urb, parent->udev,
usb_rcvbulkpipe(parent->udev, GS_USB_ENDPOINT_IN),
Expand Down Expand Up @@ -857,6 +895,8 @@ static int gs_can_open(struct net_device *netdev)
dev->hf_size_tx = struct_size(hf, classic_can, 1);
}

can_rx_offload_enable(&dev->offload);

if (!parent->active_channels) {
if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP)
gs_usb_timestamp_init(parent);
Expand Down Expand Up @@ -965,6 +1005,7 @@ static int gs_can_open(struct net_device *netdev)
gs_usb_timestamp_stop(parent);
}

can_rx_offload_disable(&dev->offload);
close_candev(netdev);

return rc;
Expand Down Expand Up @@ -1037,6 +1078,8 @@ static int gs_can_close(struct net_device *netdev)
dev->tx_context[rc].echo_id = GS_MAX_TX_URBS;
}

can_rx_offload_disable(&dev->offload);

/* close the netdev */
close_candev(netdev);

Expand Down Expand Up @@ -1336,18 +1379,21 @@ static struct gs_can *gs_make_candev(unsigned int channel,
dev->can.data_bittiming_const = &dev->data_bt_const;
}

can_rx_offload_add_manual(netdev, &dev->offload, GS_NAPI_WEIGHT);
SET_NETDEV_DEV(netdev, &intf->dev);

rc = register_candev(dev->netdev);
if (rc) {
dev_err(&intf->dev,
"Couldn't register candev for channel %d (%pe)\n",
channel, ERR_PTR(rc));
goto out_free_candev;
goto out_can_rx_offload_del;
}

return dev;

out_can_rx_offload_del:
can_rx_offload_del(&dev->offload);
out_free_candev:
free_candev(dev->netdev);
return ERR_PTR(rc);
Expand All @@ -1356,6 +1402,7 @@ static struct gs_can *gs_make_candev(unsigned int channel,
static void gs_destroy_candev(struct gs_can *dev)
{
unregister_candev(dev->netdev);
can_rx_offload_del(&dev->offload);
free_candev(dev->netdev);
}

Expand Down

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