[PATCH] sim7100: query until AT channel is ready

It's seen that the AT channel contains unknown data upon power on.
Query the modem until it answers with OK. Create a timer to re-issue
the AT command at regular intervals until the modem answers OK.

plugins/sim7100.c:sim7100_enable()
plugins/sim7100.c:open_device() devkey=AT
src/modem.c:get_modem_property() modem 0x261f20 property AT
plugins/sim7100.c:open_device() devkey=PPP
src/modem.c:get_modem_property() modem 0x261f20 property PPP
AT: > AT\r
AT: < \r\r*A
PPP: < \r\r*A
AT: < AT\r
plugins/sim7100.c:init_timeout_cb() 0x261f20
AT: > AT\r
AT: < AT\r
AT: < \r\nOK\r\n
AT: > ATE0Q0V1\r
AT: < ATE0Q0V1\r\r\nOK\r\n
AT: > AT+CGMM\r
AT: < \r\nA7672E-FASE\r\n\r\nOK\r\n
plugins/sim7100.c:cgmm_cb() modem model: A7672E-FASE
plugins/sim7100.c:cgmm_cb() before CFUN
AT: > AT+CFUN=4\r
AT: < \r\n+CGEV: ME DETACH\r\n\r\n+CGEV: NW PDN DEACT 1\r\n
PPP: < \r\n+CGEV: ME DETACH\r\n\r\n+CGEV: NW PDN DEACT 1\r\n
AT: < \r\nOK\r\n
plugins/sim7100.c:cfun_set_on_cb()
src/modem.c:modem_change_state() old state: 0, new state: 1
---

Is this the way to do it? It's quite weird that the serial channel
doesn't respond in a sane maner after power up.

Before this patch ofono would get stuck in enable and transmit CFUN=4,
our software would then restart ofono and everything would be fine
again.
I have done nearly 50 power cycles with this patch all being successful.

 plugins/sim7100.c | 75 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 62 insertions(+), 13 deletions(-)

diff --git a/plugins/sim7100.c b/plugins/sim7100.c
index b6389b09..d52e5b92 100644
--- a/plugins/sim7100.c
+++ b/plugins/sim7100.c
@@ -22,6 +22,7 @@
 #include <glib.h>
 #include <gatchat.h>
 #include <gattty.h>
+#include <ell/ell.h>
 
 #define OFONO_API_SUBJECT_TO_CHANGE
 #include <ofono/plugin.h>
@@ -57,6 +58,9 @@ struct sim7100_data {
 	GAtChat *at;
 	GAtChat *ppp;
 	enum sim7x00_model model;
+	struct l_timeout *init_timeout;
+	size_t init_count;
+	guint init_cmd;
 };
 
 static void sim7100_debug(const char *str, void *user_data)
@@ -154,6 +158,47 @@ static void cgmm_cb(gboolean ok, GAtResult *result, gpointer user_data)
 									NULL);
 }
 
+
+static void init_cmd_cb(gboolean ok, GAtResult *result, void *user_data)
+{
+	struct ofono_modem *modem = user_data;
+	struct sim7100_data *data = ofono_modem_get_data(modem);
+
+	/* ensure modem is in a known state; verbose on, echo/quiet off */
+	g_at_chat_send(data->at, "ATE0Q0V1", NULL, NULL, NULL, NULL);
+
+	g_at_chat_send(data->at, "AT+CGMM", NULL, cgmm_cb, modem, NULL);
+
+	l_timeout_remove(data->init_timeout);
+	data->init_timeout = NULL;
+}
+
+static void close_serial(struct ofono_modem *modem)
+{
+	struct sim7100_data *data = ofono_modem_get_data(modem);
+
+	g_at_chat_unref(data->ppp);
+	g_at_chat_unref(data->at);
+	data->at = data->ppp = NULL;
+}
+
+static void init_timeout_cb(struct l_timeout *timeout, void *user_data)
+{
+	struct ofono_modem *modem = user_data;
+	struct sim7100_data *data = ofono_modem_get_data(modem);
+
+	DBG("%p", modem);
+
+	if (data->init_count++ >= 30) {
+		ofono_error("failed to init modem after 30 attempts");
+		close_serial(modem);
+		return;
+	}
+
+	g_at_chat_retry(data->at, data->init_cmd);
+	l_timeout_modify_ms(timeout, 500);
+}
+
 static int open_device(struct ofono_modem *modem, char *devkey, GAtChat **chat)
 {
 	DBG("devkey=%s", devkey);
@@ -172,16 +217,22 @@ static int sim7100_enable(struct ofono_modem *modem)
 
 	DBG("");
 
-	err = open_device(modem, "AT", &data->at);
-	if (err < 0)
-		return err;
-
-	err = open_device(modem, "PPP", &data->ppp);
-	if (err < 0)
-		return err;
-
-	/* ensure modem is in a known state; verbose on, echo/quiet off */
-	g_at_chat_send(data->at, "ATE0Q0V1", NULL, NULL, NULL, NULL);
+	if (g_at_chat_get_channel(data->at) == NULL) {
+		err = open_device(modem, "AT", &data->at);
+		if (err < 0)
+			return err;
+
+		err = open_device(modem, "PPP", &data->ppp);
+		if (err < 0)
+			return err;
+
+		data->init_count = 0;
+		data->init_cmd = g_at_chat_send(data->at, "AT", NULL,
+				init_cmd_cb, modem, NULL);
+		data->init_timeout = l_timeout_create_ms(500, init_timeout_cb, modem,
+				NULL);
+		return -EINPROGRESS;
+	}
 
 	/* query modem model string */
 	g_at_chat_send(data->at, "AT+CGMM", NULL, cgmm_cb, modem, NULL);
@@ -196,9 +247,7 @@ static void cfun_set_off_cb(gboolean ok, GAtResult *result, gpointer user_data)
 
 	DBG("");
 
-	g_at_chat_unref(data->ppp);
-	g_at_chat_unref(data->at);
-	data->at = data->ppp = NULL;
+	close_serial(modem);
 
 	if (ok)
 		ofono_modem_set_powered(modem, FALSE);
-- 
2.49.0