[PATCH net-next v2] net: wwan: mhi_wwan_ctrl: say the DTR drop flush is best effort

[Peter Hunt <peter.hunt@opengear.com>]

Four comments around the DTR/RTS work don't match the code since
commit 10f51f4fb99d ("net: wwan: mhi_wwan_ctrl: send a DTR drop before
it can be coalesced"):

- the ->dtr_rts() comment says the drop is sent now, but a drop that
  hits a full UL ring or a failed allocation is retried with whatever
  state is latest by then,
- the stop() comment says pending state is sent before the channel
  stops, but the flush there makes one attempt as well, and a retry
  goes out from dtr_work after the channel has stopped,
- the dtr_mdmbits comment only describes coalescing,
- the remove() comment says the removal drop gets one attempt, but the
  drop and stop() paths now flush the work as well.

Update them. No functional change.

Link: https://lore.kernel.org/all/179340002701.3131.15535297427661129303@kernel.org/
Signed-off-by: Peter Hunt <peter.hunt@opengear.com>
---
Changes in v2:
- Also update the stop() comment, its flush makes one attempt too.
- Name a failed allocation as well as a full UL ring as a retry cause.
- v1: https://lore.kernel.org/all/20261109185731.182990-1-peter.hunt@opengear.com/

 drivers/net/wwan/mhi_wwan_ctrl.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
index 772319927867..387ab1bb0c41 100644
--- a/drivers/net/wwan/mhi_wwan_ctrl.c
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c
@@ -68,7 +68,8 @@ struct mhi_wwan_dev {
 	unsigned int rx_budget;
 
 	/* Latest DTR/RTS state for the modem, sent from dtr_work so a burst of
-	 * changes is coalesced and only the final state has to get through
+	 * changes is coalesced and only the final state has to get through.
+	 * A DTR drop is flushed out on its own, see mhi_wwan_ctrl_dtr_rts().
 	 */
 	unsigned int dtr_mdmbits;
 	struct delayed_work dtr_work;
@@ -216,7 +217,9 @@ static void mhi_wwan_ctrl_dtr_rts(struct wwan_port *port, unsigned int mdmbits)
 	schedule_delayed_work(&mhiwwan->dtr_work, 0);
 
 	/* A DTR drop matters on its own, e.g. to hang up a modem set to AT&D2,
-	 * so send it now rather than let a following raise coalesce it away
+	 * so try to send it now rather than let a following raise coalesce it
+	 * away. This is best effort, a drop that hits a full UL ring or a failed
+	 * allocation is retried with whatever state is latest by then.
 	 */
 	if (drop)
 		flush_delayed_work(&mhiwwan->dtr_work);
@@ -254,7 +257,10 @@ static void mhi_wwan_ctrl_stop(struct wwan_port *port)
 
 	cancel_work_sync(&mhiwwan->rx_refill);
 
-	/* Send any pending DTR/RTS state before the channel stops */
+	/* Try to send any pending DTR/RTS state before the channel stops. This
+	 * is best effort too, a send that has to be retried goes out from
+	 * dtr_work after the channel has stopped.
+	 */
 	flush_delayed_work(&mhiwwan->dtr_work);
 
 	mhi_unprepare_from_transfer(mhiwwan->mhi_dev);
@@ -376,7 +382,7 @@ static void mhi_wwan_ctrl_remove(struct mhi_device *mhi_dev)
 	struct mhi_wwan_dev *mhiwwan = dev_get_drvdata(&mhi_dev->dev);
 
 	wwan_remove_port(mhiwwan->wwan_port);
-	/* Give the DTR/RTS drop from removal one attempt, then stop the work */
+	/* Give any pending DTR/RTS state a last attempt, then stop the work */
 	flush_delayed_work(&mhiwwan->dtr_work);
 	disable_delayed_work_sync(&mhiwwan->dtr_work);
 	kfree(mhiwwan);
-- 
2.43.0