remoteproc: sysmon: Wait for SSCTL service to come up

The SSCTL service comes up after a finite time when the remote Q6 comes
out of reset. Any graceful shutdowns requested during this period will
be a NOP and abrupt tearing down of the glink channel might lead to pending
transactions on the remote Q6 side and will ultimately lead to a fatal
error. Fix this by waiting for the SSCTL service when a graceful shutdown
is requested.

Fixes: 1fb82ee8 ("remoteproc: qcom: Introduce sysmon")
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1657022900-2049-7-git-send-email-quic_sibis@quicinc.com

drivers/remoteproc/qcom_sysmon.c

@@ -41,6 +41,7 @@ struct qcom_sysmon {
 	struct completion comp;
 	struct completion ind_comp;
 	struct completion shutdown_comp;
+	struct completion ssctl_comp;
 	struct mutex lock;
 
 	bool ssr_ack;
@@ -445,6 +446,8 @@ static int ssctl_new_server(struct qmi_handle *qmi, struct qmi_service *svc)
 
 	svc->priv = sysmon;
 
+	complete(&sysmon->ssctl_comp);
+
 	return 0;
 }
 
@@ -501,6 +504,7 @@ static int sysmon_start(struct rproc_subdev *subdev)
 		.ssr_event = SSCTL_SSR_EVENT_AFTER_POWERUP
 	};
 
+	reinit_completion(&sysmon->ssctl_comp);
 	mutex_lock(&sysmon->state_lock);
 	sysmon->state = SSCTL_SSR_EVENT_AFTER_POWERUP;
 	blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);
@@ -545,6 +549,11 @@ static void sysmon_stop(struct rproc_subdev *subdev, bool crashed)
 	if (crashed)
 		return;
 
+	if (sysmon->ssctl_instance) {
+		if (!wait_for_completion_timeout(&sysmon->ssctl_comp, HZ / 2))
+			dev_err(sysmon->dev, "timeout waiting for ssctl service\n");
+	}
+
 	if (sysmon->ssctl_version)
 		sysmon->shutdown_acked = ssctl_request_shutdown(sysmon);
 	else if (sysmon->ept)
@@ -631,6 +640,7 @@ struct qcom_sysmon *qcom_add_sysmon_subdev(struct rproc *rproc,
 	init_completion(&sysmon->comp);
 	init_completion(&sysmon->ind_comp);
 	init_completion(&sysmon->shutdown_comp);
+	init_completion(&sysmon->ssctl_comp);
 	mutex_init(&sysmon->lock);
 	mutex_init(&sysmon->state_lock);