[PATCH can v2] can: gs_usb: fix hardware timestamp state for mixed channels

[Shuangpeng Bai <shuangpeng.kernel@gmail.com>]

The hardware timestamp state is shared by struct gs_usb, but gs_can_open()
and gs_can_close() tie its initialization and teardown to active_channels
and to the feature bits of the channel being opened or closed.

This is wrong for mixed-channel devices in both directions. If a
non-timestamp channel opens first, a later timestamp-capable channel does
not initialize the shared cyclecounter/timecounter because active_channels
is already non-zero. Timestamp RX then calls timecounter_cyc2time() with
parent->tc.cc unset.

Conversely, if a timestamp-capable channel opens first and starts the
shared delayed work, then closes while a non-timestamp channel remains
active, disconnect may close the non-timestamp channel last. The old
teardown check skips gs_usb_timestamp_stop() in that case and frees
struct gs_usb while the delayed work timer is still queued.

Count the number of active timestamp-capable channels. Start the shared
timestamp worker when the first such channel opens, stop it when the last
such channel closes, and unwind the count if open fails.

Fixes: 45dfa45f52e6 ("can: gs_usb: add RX and TX hardware timestamp support")
Cc: stable@vger.kernel.org
Suggested-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
---
Changes in v2:
- Count active timestamp-capable channels instead of tracking only whether
  the shared timestamp worker has been started.
- Stop the shared timestamp worker when the last timestamp-capable channel
  closes, even if non-timestamp channels remain open.
- Unwind the timestamp-capable channel count on gs_can_open() failures.

 drivers/net/can/usb/gs_usb.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
index ec9a7cbbbc69..9cc197803e0d 100644
--- a/drivers/net/can/usb/gs_usb.c
+++ b/drivers/net/can/usb/gs_usb.c
@@ -337,6 +337,7 @@ struct gs_usb {
 
 	unsigned int hf_size_rx;
 	u8 active_channels;
+	u8 active_timestamp_channels;
 	u8 channel_cnt;
 
 	unsigned int pipe_in;
@@ -980,10 +981,13 @@ static int gs_can_open(struct net_device *netdev)
 
 	can_rx_offload_enable(&dev->offload);
 
-	if (!parent->active_channels) {
-		if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP)
+	if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) {
+		if (!parent->active_timestamp_channels)
 			gs_usb_timestamp_init(parent);
+		parent->active_timestamp_channels++;
+	}
 
+	if (!parent->active_channels) {
 		for (i = 0; i < GS_MAX_RX_URBS; i++) {
 			u8 *buf;
 
@@ -1094,13 +1098,15 @@ static int gs_can_open(struct net_device *netdev)
 out_usb_free_urb:
 	usb_free_urb(urb);
 out_usb_kill_anchored_urbs:
-	if (!parent->active_channels) {
-		usb_kill_anchored_urbs(&parent->rx_submitted);
-
-		if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP)
+	if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) {
+		parent->active_timestamp_channels--;
+		if (!parent->active_timestamp_channels)
 			gs_usb_timestamp_stop(parent);
 	}
 
+	if (!parent->active_channels)
+		usb_kill_anchored_urbs(&parent->rx_submitted);
+
 	can_rx_offload_disable(&dev->offload);
 	close_candev(netdev);
 
@@ -1152,13 +1158,15 @@ static int gs_can_close(struct net_device *netdev)
 
 	/* Stop polling */
 	parent->active_channels--;
-	if (!parent->active_channels) {
-		usb_kill_anchored_urbs(&parent->rx_submitted);
-
-		if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP)
+	if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP) {
+		parent->active_timestamp_channels--;
+		if (!parent->active_timestamp_channels)
 			gs_usb_timestamp_stop(parent);
 	}
 
+	if (!parent->active_channels)
+		usb_kill_anchored_urbs(&parent->rx_submitted);
+
 	/* Stop sending URBs */
 	usb_kill_anchored_urbs(&dev->tx_submitted);
 	atomic_set(&dev->active_tx_urbs, 0);
-- 
2.43.0