[OpenWrt-Devel] [PATCH] uqmi: add timeout parameter

[Zefir Kurtisi]

Working with Quectel EM12 LTE-module, we observe
regular stalls of the QMI interface which cause
a request issued by uqmi to hang forever.

Most reproducibly this happens after the device
has been power-cycled and left untouched for a
while (~ 60s+). Most of the time the very first
QMI request fails, since it is not responded by
the module. This is the strace from such a run
(from --get-pin-status):

 open("/dev/cdc-wdm0", O_RDWR|O_EXCL|O_NOCTTY|O_NONBLOCK|O_LARGEFILE) = 6
 fcntl64(6, F_GETFL)                     = 0x10802 (flags O_RDWR|O_NONBLOCK|O_LARGEFILE)
 fcntl64(6, F_SETFL, O_RDWR|O_NONBLOCK|O_LARGEFILE) = 0
 epoll_ctl(3, EPOLL_CTL_ADD, 6, {EPOLLIN|EPOLLRDHUP|EPOLLET, {u32=268567076, u64=1153486808202346496}}) = 0
 write(6, "\1\17\0\0\0\0\0\1\"\0\4\0\1\1\0\2", 16) = 16
 clock_gettime(CLOCK_MONOTONIC, {tv_sec=95, tv_nsec=583444789}) = 0
 clock_gettime(CLOCK_MONOTONIC, {tv_sec=95, tv_nsec=583770264}) = 0
 epoll_pwait(3,
 [ hang forever ]

After killing the blocked uqmi process, the next
request works as expected.

We don't know whether this is a device FW issue
(we use the latest EM12GPAR01A15M4G) or whether
the device enters some undocumented power-save
mode after idling for some time.

This patch extends uqmi with a timeout option
(-t, --timeout <ms>) which if set terminates a
request after the given amount of msecs. In
our usecase it provides a means of preventing
infinitively stuck QMI requests. Since we
observe the issue only for the very first
request after cold-boot, we use a dummy access
early in qmi.sh, e.g.
  uqmi -d /dev/cdc-wdm0 --get-pin-status -t 3000 >/dev/null 2>&1

This ensures the QMI interface is un-stuck in
case it entered the stall-state observed. The
change is intentionally not included in this
commit, since you don't need it if it works
for you.


Signed-off-by: Zefir Kurtisi <zefir.kurtisi at neratec.com>
---
 main.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/main.c b/main.c
index 9b43e5e..aa4634c 100644
--- a/main.c
+++ b/main.c
@@ -44,6 +44,7 @@ static const struct option uqmi_getopt[] = {
 	{ "keep-client-id", required_argument, NULL, 'k' },
 	{ "release-client-id", required_argument, NULL, 'r' },
 	{ "mbim",  no_argument, NULL, 'm' },
+	{ "timeout", required_argument, NULL, 't' },
 	{ NULL, 0, NULL, 0 }
 };
 #undef __uqmi_command
@@ -57,6 +58,7 @@ static int usage(const char *progname)
 		"  --keep-client-id <name>:          Keep Client ID for service <name>\n"
 		"  --release-client-id <name>:       Release Client ID after exiting\n"
 		"  --mbim, -m                        NAME is an MBIM device with EXT_QMUX support\n"
+		"  --timeout, -t                     response timeout in msecs\n"
 		"\n"
 		"Services:                           dms, nas, pds, wds, wms\n"
 		"\n"
@@ -103,6 +105,14 @@ static void handle_exit_signal(int signal)
 	uloop_end();
 }
 
+static void _request_timeout_handler(struct uloop_timeout *timeout)
+{
+	fprintf(stderr, "Request timed out\n");
+	handle_exit_signal(0);
+}
+
+struct uloop_timeout request_timeout = { .cb = _request_timeout_handler, };
+
 int main(int argc, char **argv)
 {
 	static struct qmi_dev dev;
@@ -112,7 +122,7 @@ int main(int argc, char **argv)
 	signal(SIGINT, handle_exit_signal);
 	signal(SIGTERM, handle_exit_signal);
 
-	while ((ch = getopt_long(argc, argv, "d:k:sm", uqmi_getopt, NULL)) != -1) {
+	while ((ch = getopt_long(argc, argv, "d:k:smt:", uqmi_getopt, NULL)) != -1) {
 		int cmd_opt = CMD_OPT(ch);
 
 		if (ch < 0 && cmd_opt >= 0 && cmd_opt < __UQMI_COMMAND_LAST) {
@@ -136,6 +146,9 @@ int main(int argc, char **argv)
 		case 'm':
 			dev.is_mbim = true;
 			break;
+		case 't':
+			uloop_timeout_set(&request_timeout, atol(optarg));
+			break;
 		default:
 			return usage(argv[0]);
 		}
-- 
2.17.1


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