Subject: [PATCH net-next 5/6] net: ipa: retry modem stop if busy

From: Alex Elder <[email-masked]>
Date: Thu, 19 Nov 2020 16:49:28 -0600

The IPA driver remove callback, ipa_remove(), calls ipa_modem_stop()
if the setup stage of initialization is complete.  If a concurrent
call to ipa_modem_start() or ipa_modem_stop() has begin but not
completed, ipa_modem_stop() can return an error (-EBUSY).

The next patch adds a driver shutdown callback, which will simply
call ipa_remove().  We really want our shutdown callback to clean
things up.  So add a single retry to the ipa_modem_stop() call in
ipa_remove() after a short (millisecond) delay.  This offers no
guarantee the shutdown will complete successfully, but we'll at
least try a little harder before giving up.

Signed-off-by: Alex Elder <[email-masked]>
---
 drivers/net/ipa/ipa_main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ipa/ipa_main.c b/drivers/net/ipa/ipa_main.c
index 3fb9c5d90b70e..9f4bd822ac625 100644
--- a/drivers/net/ipa/ipa_main.c
+++ b/drivers/net/ipa/ipa_main.c
@@ -864,6 +864,11 @@ static int ipa_remove(struct platform_device *pdev)
 
 	if (ipa->setup_complete) {
 		ret = ipa_modem_stop(ipa);
+		/* If starting or stopping is in progress, try once more */
+		if (ret == -EBUSY) {
+			usleep_range(USEC_PER_MSEC, 2 * USEC_PER_MSEC);
+			ret = ipa_modem_stop(ipa);
+		}
 		if (ret)
 			return ret;
 
-- 
2.20.1