[PATCH v5 4/5] remoteproc: qcom: Introduce sysmon

[Bjorn Andersson <bjorn.andersson@linaro.org>]

The sysmon client communicates either via a dedicated SMD/GLINK channel
or via QMI encoded messages over IPCROUTER with remote processors in
order to perform graceful shutdown and inform about other remote
processors shutting down.

Acked-by: Chris Lew <clew@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

Changes since v4:
- SPDX header

Changes since v3:
- Kerneldoc updates
- Style fixes

Changes since v2:
- Checkpatch fixes

Changes since v1:
- New patch

 drivers/remoteproc/Kconfig         |  17 ++
 drivers/remoteproc/Makefile        |   1 +
 drivers/remoteproc/qcom_adsp_pil.c |  12 +
 drivers/remoteproc/qcom_common.h   |  21 ++
 drivers/remoteproc/qcom_q6v5_pil.c |   3 +
 drivers/remoteproc/qcom_sysmon.c   | 579 +++++++++++++++++++++++++++++++++++++
 drivers/remoteproc/qcom_wcnss.c    |   4 +
 7 files changed, 637 insertions(+)
 create mode 100644 drivers/remoteproc/qcom_sysmon.c

diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
index b609e1d3654b..6556df21318e 100644
--- a/drivers/remoteproc/Kconfig
+++ b/drivers/remoteproc/Kconfig
@@ -90,6 +90,7 @@ config QCOM_ADSP_PIL
 	depends on QCOM_SMEM
 	depends on RPMSG_QCOM_SMD || (COMPILE_TEST && RPMSG_QCOM_SMD=n)
 	depends on RPMSG_QCOM_GLINK_SMEM || RPMSG_QCOM_GLINK_SMEM=n
+	depends on QCOM_SYSMON || QCOM_SYSMON=n
 	select MFD_SYSCON
 	select QCOM_MDT_LOADER
 	select QCOM_RPROC_COMMON
@@ -107,6 +108,7 @@ config QCOM_Q6V5_PIL
 	depends on QCOM_SMEM
 	depends on RPMSG_QCOM_SMD || (COMPILE_TEST && RPMSG_QCOM_SMD=n)
 	depends on RPMSG_QCOM_GLINK_SMEM || RPMSG_QCOM_GLINK_SMEM=n
+	depends on QCOM_SYSMON || QCOM_SYSMON=n
 	select MFD_SYSCON
 	select QCOM_RPROC_COMMON
 	select QCOM_SCM
@@ -114,12 +116,27 @@ config QCOM_Q6V5_PIL
 	  Say y here to support the Qualcomm Peripherial Image Loader for the
 	  Hexagon V5 based remote processors.
 
+config QCOM_SYSMON
+	tristate "Qualcomm sysmon driver"
+	depends on RPMSG
+	depends on ARCH_QCOM
+	select QCOM_QMI_HELPERS
+	help
+	  The sysmon driver implements a sysmon QMI client and a handler for
+	  the sys_mon SMD and GLINK channel, which are used for graceful
+	  shutdown, retrieving failure information and propagating information
+	  about other subsystems being shut down.
+
+	  Say y here if your system runs firmware on any other subsystems, e.g.
+	  modem or DSP.
+
 config QCOM_WCNSS_PIL
 	tristate "Qualcomm WCNSS Peripheral Image Loader"
 	depends on OF && ARCH_QCOM
 	depends on RPMSG_QCOM_SMD || (COMPILE_TEST && RPMSG_QCOM_SMD=n)
 	depends on RPMSG_QCOM_GLINK_SMEM || RPMSG_QCOM_GLINK_SMEM=n
 	depends on QCOM_SMEM
+	depends on QCOM_SYSMON || QCOM_SYSMON=n
 	select QCOM_MDT_LOADER
 	select QCOM_RPROC_COMMON
 	select QCOM_SCM
diff --git a/drivers/remoteproc/Makefile b/drivers/remoteproc/Makefile
index 6e16450ce11f..02627ede8d4a 100644
--- a/drivers/remoteproc/Makefile
+++ b/drivers/remoteproc/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_KEYSTONE_REMOTEPROC)	+= keystone_remoteproc.o
 obj-$(CONFIG_QCOM_ADSP_PIL)		+= qcom_adsp_pil.o
 obj-$(CONFIG_QCOM_RPROC_COMMON)		+= qcom_common.o
 obj-$(CONFIG_QCOM_Q6V5_PIL)		+= qcom_q6v5_pil.o
+obj-$(CONFIG_QCOM_SYSMON)		+= qcom_sysmon.o
 obj-$(CONFIG_QCOM_WCNSS_PIL)		+= qcom_wcnss_pil.o
 qcom_wcnss_pil-y			+= qcom_wcnss.o
 qcom_wcnss_pil-y			+= qcom_wcnss_iris.o
diff --git a/drivers/remoteproc/qcom_adsp_pil.c b/drivers/remoteproc/qcom_adsp_pil.c
index 3f6af54dbc96..45e7e66604d4 100644
--- a/drivers/remoteproc/qcom_adsp_pil.c
+++ b/drivers/remoteproc/qcom_adsp_pil.c
@@ -38,7 +38,10 @@ struct adsp_data {
 	const char *firmware_name;
 	int pas_id;
 	bool has_aggre2_clk;
+
 	const char *ssr_name;
+	const char *sysmon_name;
+	int ssctl_id;
 };
 
 struct qcom_adsp {
@@ -75,6 +78,7 @@ struct qcom_adsp {
 	struct qcom_rproc_glink glink_subdev;
 	struct qcom_rproc_subdev smd_subdev;
 	struct qcom_rproc_ssr ssr_subdev;
+	struct qcom_sysmon *sysmon;
 };
 
 static int adsp_load(struct rproc *rproc, const struct firmware *fw)
@@ -404,6 +408,9 @@ static int adsp_probe(struct platform_device *pdev)
 	qcom_add_glink_subdev(rproc, &adsp->glink_subdev);
 	qcom_add_smd_subdev(rproc, &adsp->smd_subdev);
 	qcom_add_ssr_subdev(rproc, &adsp->ssr_subdev, desc->ssr_name);
+	adsp->sysmon = qcom_add_sysmon_subdev(rproc,
+					      desc->sysmon_name,
+					      desc->ssctl_id);
 
 	ret = rproc_add(rproc);
 	if (ret)
@@ -425,6 +432,7 @@ static int adsp_remove(struct platform_device *pdev)
 	rproc_del(adsp->rproc);
 
 	qcom_remove_glink_subdev(adsp->rproc, &adsp->glink_subdev);
+	qcom_remove_sysmon_subdev(adsp->sysmon);
 	qcom_remove_smd_subdev(adsp->rproc, &adsp->smd_subdev);
 	qcom_remove_ssr_subdev(adsp->rproc, &adsp->ssr_subdev);
 	rproc_free(adsp->rproc);
@@ -438,6 +446,8 @@ static const struct adsp_data adsp_resource_init = {
 		.pas_id = 1,
 		.has_aggre2_clk = false,
 		.ssr_name = "lpass",
+		.sysmon_name = "adsp",
+		.ssctl_id = 0x14,
 };
 
 static const struct adsp_data slpi_resource_init = {
@@ -446,6 +456,8 @@ static const struct adsp_data slpi_resource_init = {
 		.pas_id = 12,
 		.has_aggre2_clk = true,
 		.ssr_name = "dsps",
+		.sysmon_name = "slpi",
+		.ssctl_id = 0x16,
 };
 
 static const struct of_device_id adsp_of_match[] = {
diff --git a/drivers/remoteproc/qcom_common.h b/drivers/remoteproc/qcom_common.h
index 832e20271664..541586e528b3 100644
--- a/drivers/remoteproc/qcom_common.h
+++ b/drivers/remoteproc/qcom_common.h
@@ -4,6 +4,9 @@
 
 #include <linux/remoteproc.h>
 #include "remoteproc_internal.h"
+#include <linux/soc/qcom/qmi.h>
+
+struct qcom_sysmon;
 
 struct qcom_rproc_glink {
 	struct rproc_subdev subdev;
@@ -41,4 +44,22 @@ void qcom_add_ssr_subdev(struct rproc *rproc, struct qcom_rproc_ssr *ssr,
 			 const char *ssr_name);
 void qcom_remove_ssr_subdev(struct rproc *rproc, struct qcom_rproc_ssr *ssr);
 
+#if IS_ENABLED(CONFIG_QCOM_SYSMON)
+struct qcom_sysmon *qcom_add_sysmon_subdev(struct rproc *rproc,
+					   const char *name,
+					   int ssctl_instance);
+void qcom_remove_sysmon_subdev(struct qcom_sysmon *sysmon);
+#else
+static inline struct qcom_sysmon *qcom_add_sysmon_subdev(struct rproc *rproc,
+							 const char *name,
+							 int ssctl_instance)
+{
+	return NULL;
+}
+
+static inline void qcom_remove_sysmon_subdev(struct qcom_sysmon *sysmon)
+{
+}
+#endif
+
 #endif
diff --git a/drivers/remoteproc/qcom_q6v5_pil.c b/drivers/remoteproc/qcom_q6v5_pil.c
index 8a3fa2bcc9f6..342d5eb5d6ed 100644
--- a/drivers/remoteproc/qcom_q6v5_pil.c
+++ b/drivers/remoteproc/qcom_q6v5_pil.c
@@ -168,6 +168,7 @@ struct q6v5 {
 
 	struct qcom_rproc_subdev smd_subdev;
 	struct qcom_rproc_ssr ssr_subdev;
+	struct qcom_sysmon *sysmon;
 	bool need_mem_protection;
 	int mpss_perm;
 	int mba_perm;
@@ -1231,6 +1232,7 @@ static int q6v5_probe(struct platform_device *pdev)
 	qproc->mba_perm = BIT(QCOM_SCM_VMID_HLOS);
 	qcom_add_smd_subdev(rproc, &qproc->smd_subdev);
 	qcom_add_ssr_subdev(rproc, &qproc->ssr_subdev, "mpss");
+	qproc->sysmon = qcom_add_sysmon_subdev(rproc, "modem", 0x12);
 
 	ret = rproc_add(rproc);
 	if (ret)
@@ -1250,6 +1252,7 @@ static int q6v5_remove(struct platform_device *pdev)
 
 	rproc_del(qproc->rproc);
 
+	qcom_remove_sysmon_subdev(qproc->sysmon);
 	qcom_remove_smd_subdev(qproc->rproc, &qproc->smd_subdev);
 	qcom_remove_ssr_subdev(qproc->rproc, &qproc->ssr_subdev);
 	rproc_free(qproc->rproc);
diff --git a/drivers/remoteproc/qcom_sysmon.c b/drivers/remoteproc/qcom_sysmon.c
new file mode 100644
index 000000000000..210914814654
--- /dev/null
+++ b/drivers/remoteproc/qcom_sysmon.c
@@ -0,0 +1,579 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2017, Linaro Ltd.
+ */
+#include <linux/firmware.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/notifier.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/remoteproc/qcom_rproc.h>
+#include <linux/rpmsg.h>
+
+#include "qcom_common.h"
+
+static BLOCKING_NOTIFIER_HEAD(sysmon_notifiers);
+
+struct qcom_sysmon {
+	struct rproc_subdev subdev;
+	struct rproc *rproc;
+
+	struct list_head node;
+
+	const char *name;
+
+	int ssctl_version;
+	int ssctl_instance;
+
+	struct notifier_block nb;
+
+	struct device *dev;
+
+	struct rpmsg_endpoint *ept;
+	struct completion comp;
+	struct mutex lock;
+
+	bool ssr_ack;
+
+	struct qmi_handle qmi;
+	struct sockaddr_qrtr ssctl;
+};
+
+static DEFINE_MUTEX(sysmon_lock);
+static LIST_HEAD(sysmon_list);
+
+/**
+ * sysmon_send_event() - send notification of other remote's SSR event
+ * @sysmon:	sysmon context
+ * @name:	other remote's name
+ */
+static void sysmon_send_event(struct qcom_sysmon *sysmon, const char *name)
+{
+	char req[50];
+	int len;
+	int ret;
+
+	len = snprintf(req, sizeof(req), "ssr:%s:before_shutdown", name);
+	if (len >= sizeof(req))
+		return;
+
+	mutex_lock(&sysmon->lock);
+	reinit_completion(&sysmon->comp);
+	sysmon->ssr_ack = false;
+
+	ret = rpmsg_send(sysmon->ept, req, len);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to send sysmon event\n");
+		goto out_unlock;
+	}
+
+	ret = wait_for_completion_timeout(&sysmon->comp,
+					  msecs_to_jiffies(5000));
+	if (!ret) {
+		dev_err(sysmon->dev, "timeout waiting for sysmon ack\n");
+		goto out_unlock;
+	}
+
+	if (!sysmon->ssr_ack)
+		dev_err(sysmon->dev, "unexpected response to sysmon event\n");
+
+out_unlock:
+	mutex_unlock(&sysmon->lock);
+}
+
+/**
+ * sysmon_request_shutdown() - request graceful shutdown of remote
+ * @sysmon:	sysmon context
+ */
+static void sysmon_request_shutdown(struct qcom_sysmon *sysmon)
+{
+	char *req = "ssr:shutdown";
+	int ret;
+
+	mutex_lock(&sysmon->lock);
+	reinit_completion(&sysmon->comp);
+	sysmon->ssr_ack = false;
+
+	ret = rpmsg_send(sysmon->ept, req, strlen(req) + 1);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "send sysmon shutdown request failed\n");
+		goto out_unlock;
+	}
+
+	ret = wait_for_completion_timeout(&sysmon->comp,
+					  msecs_to_jiffies(5000));
+	if (!ret) {
+		dev_err(sysmon->dev, "timeout waiting for sysmon ack\n");
+		goto out_unlock;
+	}
+
+	if (!sysmon->ssr_ack)
+		dev_err(sysmon->dev,
+			"unexpected response to sysmon shutdown request\n");
+
+out_unlock:
+	mutex_unlock(&sysmon->lock);
+}
+
+static int sysmon_callback(struct rpmsg_device *rpdev, void *data, int count,
+			   void *priv, u32 addr)
+{
+	struct qcom_sysmon *sysmon = priv;
+	const char *ssr_ack = "ssr:ack";
+	const int ssr_ack_len = strlen(ssr_ack) + 1;
+
+	if (!sysmon)
+		return -EINVAL;
+
+	if (count >= ssr_ack_len && !memcmp(data, ssr_ack, ssr_ack_len))
+		sysmon->ssr_ack = true;
+
+	complete(&sysmon->comp);
+
+	return 0;
+}
+
+#define SSCTL_SHUTDOWN_REQ		0x21
+#define SSCTL_SUBSYS_EVENT_REQ		0x23
+
+#define SSCTL_MAX_MSG_LEN		7
+
+#define SSCTL_SUBSYS_NAME_LENGTH	15
+
+enum {
+	SSCTL_SSR_EVENT_BEFORE_POWERUP,
+	SSCTL_SSR_EVENT_AFTER_POWERUP,
+	SSCTL_SSR_EVENT_BEFORE_SHUTDOWN,
+	SSCTL_SSR_EVENT_AFTER_SHUTDOWN,
+};
+
+enum {
+	SSCTL_SSR_EVENT_FORCED,
+	SSCTL_SSR_EVENT_GRACEFUL,
+};
+
+struct ssctl_shutdown_resp {
+	struct qmi_response_type_v01 resp;
+};
+
+static struct qmi_elem_info ssctl_shutdown_resp_ei[] = {
+	{
+		.data_type	= QMI_STRUCT,
+		.elem_len	= 1,
+		.elem_size	= sizeof(struct qmi_response_type_v01),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x02,
+		.offset		= offsetof(struct ssctl_shutdown_resp, resp),
+		.ei_array	= qmi_response_type_v01_ei,
+	},
+	{}
+};
+
+struct ssctl_subsys_event_req {
+	u8 subsys_name_len;
+	char subsys_name[SSCTL_SUBSYS_NAME_LENGTH];
+	u32 event;
+	u8 evt_driven_valid;
+	u32 evt_driven;
+};
+
+static struct qmi_elem_info ssctl_subsys_event_req_ei[] = {
+	{
+		.data_type	= QMI_DATA_LEN,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint8_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x01,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   subsys_name_len),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_UNSIGNED_1_BYTE,
+		.elem_len	= SSCTL_SUBSYS_NAME_LENGTH,
+		.elem_size	= sizeof(char),
+		.array_type	= VAR_LEN_ARRAY,
+		.tlv_type	= 0x01,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   subsys_name),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_SIGNED_4_BYTE_ENUM,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint32_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x02,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   event),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_OPT_FLAG,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint8_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x10,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   evt_driven_valid),
+		.ei_array	= NULL,
+	},
+	{
+		.data_type	= QMI_SIGNED_4_BYTE_ENUM,
+		.elem_len	= 1,
+		.elem_size	= sizeof(uint32_t),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x10,
+		.offset		= offsetof(struct ssctl_subsys_event_req,
+					   evt_driven),
+		.ei_array	= NULL,
+	},
+	{}
+};
+
+struct ssctl_subsys_event_resp {
+	struct qmi_response_type_v01 resp;
+};
+
+static struct qmi_elem_info ssctl_subsys_event_resp_ei[] = {
+	{
+		.data_type	= QMI_STRUCT,
+		.elem_len	= 1,
+		.elem_size	= sizeof(struct qmi_response_type_v01),
+		.array_type	= NO_ARRAY,
+		.tlv_type	= 0x02,
+		.offset		= offsetof(struct ssctl_subsys_event_resp,
+					   resp),
+		.ei_array	= qmi_response_type_v01_ei,
+	},
+	{}
+};
+
+/**
+ * ssctl_request_shutdown() - request shutdown via SSCTL QMI service
+ * @sysmon:	sysmon context
+ */
+static void ssctl_request_shutdown(struct qcom_sysmon *sysmon)
+{
+	struct ssctl_shutdown_resp resp;
+	struct qmi_txn txn;
+	int ret;
+
+	ret = qmi_txn_init(&sysmon->qmi, &txn, ssctl_shutdown_resp_ei, &resp);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to allocate QMI txn\n");
+		return;
+	}
+
+	ret = qmi_send_request(&sysmon->qmi, &sysmon->ssctl, &txn,
+			       SSCTL_SHUTDOWN_REQ, 0, NULL, NULL);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to send shutdown request\n");
+		qmi_txn_cancel(&txn);
+		return;
+	}
+
+	ret = qmi_txn_wait(&txn, 5 * HZ);
+	if (ret < 0)
+		dev_err(sysmon->dev, "failed receiving QMI response\n");
+	else if (resp.resp.result)
+		dev_err(sysmon->dev, "shutdown request failed\n");
+	else
+		dev_dbg(sysmon->dev, "shutdown request completed\n");
+}
+
+/**
+ * ssctl_send_event() - send notification of other remote's SSR event
+ * @sysmon:	sysmon context
+ * @name:	other remote's name
+ */
+static void ssctl_send_event(struct qcom_sysmon *sysmon, const char *name)
+{
+	struct ssctl_subsys_event_resp resp;
+	struct ssctl_subsys_event_req req;
+	struct qmi_txn txn;
+	int ret;
+
+	memset(&resp, 0, sizeof(resp));
+	ret = qmi_txn_init(&sysmon->qmi, &txn, ssctl_subsys_event_resp_ei, &resp);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to allocate QMI txn\n");
+		return;
+	}
+
+	memset(&req, 0, sizeof(req));
+	strlcpy(req.subsys_name, name, sizeof(req.subsys_name));
+	req.subsys_name_len = strlen(req.subsys_name);
+	req.event = SSCTL_SSR_EVENT_BEFORE_SHUTDOWN;
+	req.evt_driven_valid = true;
+	req.evt_driven = SSCTL_SSR_EVENT_FORCED;
+
+	ret = qmi_send_request(&sysmon->qmi, &sysmon->ssctl, &txn,
+			       SSCTL_SUBSYS_EVENT_REQ, 40,
+			       ssctl_subsys_event_req_ei, &req);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to send shutdown request\n");
+		qmi_txn_cancel(&txn);
+		return;
+	}
+
+	ret = qmi_txn_wait(&txn, 5 * HZ);
+	if (ret < 0)
+		dev_err(sysmon->dev, "failed receiving QMI response\n");
+	else if (resp.resp.result)
+		dev_err(sysmon->dev, "ssr event send failed\n");
+	else
+		dev_dbg(sysmon->dev, "ssr event send completed\n");
+}
+
+/**
+ * ssctl_new_server() - QMI callback indicating a new service
+ * @qmi:	QMI handle
+ * @svc:	service information
+ *
+ * Return: 0 if we're interested in this service, -EINVAL otherwise.
+ */
+static int ssctl_new_server(struct qmi_handle *qmi, struct qmi_service *svc)
+{
+	struct qcom_sysmon *sysmon = container_of(qmi, struct qcom_sysmon, qmi);
+
+	switch (svc->version) {
+	case 1:
+		if (svc->instance != 0)
+			return -EINVAL;
+		if (strcmp(sysmon->name, "modem"))
+			return -EINVAL;
+		break;
+	case 2:
+		if (svc->instance != sysmon->ssctl_instance)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	};
+
+	sysmon->ssctl_version = svc->version;
+
+	sysmon->ssctl.sq_family = AF_QIPCRTR;
+	sysmon->ssctl.sq_node = svc->node;
+	sysmon->ssctl.sq_port = svc->port;
+
+	svc->priv = sysmon;
+
+	return 0;
+}
+
+/**
+ * ssctl_del_server() - QMI callback indicating that @svc is removed
+ * @qmi:	QMI handle
+ * @svc:	service information
+ */
+static void ssctl_del_server(struct qmi_handle *qmi, struct qmi_service *svc)
+{
+	struct qcom_sysmon *sysmon = svc->priv;
+
+	sysmon->ssctl_version = 0;
+}
+
+static const struct qmi_ops ssctl_ops = {
+	.new_server = ssctl_new_server,
+	.del_server = ssctl_del_server,
+};
+
+static int sysmon_start(struct rproc_subdev *subdev)
+{
+	return 0;
+}
+
+static void sysmon_stop(struct rproc_subdev *subdev, bool graceful)
+{
+	struct qcom_sysmon *sysmon = container_of(subdev, struct qcom_sysmon, subdev);
+
+	blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)sysmon->name);
+
+	/* Don't request graceful shutdown if we've crashed */
+	if (!graceful)
+		return;
+
+	if (sysmon->ssctl_version)
+		ssctl_request_shutdown(sysmon);
+	else if (sysmon->ept)
+		sysmon_request_shutdown(sysmon);
+}
+
+/**
+ * sysmon_notify() - notify sysmon target of another's SSR
+ * @nb:		notifier_block associated with sysmon instance
+ * @event:	unused
+ * @data:	SSR identifier of the remote that is going down
+ */
+static int sysmon_notify(struct notifier_block *nb, unsigned long event,
+			 void *data)
+{
+	struct qcom_sysmon *sysmon = container_of(nb, struct qcom_sysmon, nb);
+	struct rproc *rproc = sysmon->rproc;
+	const char *ssr_name = data;
+
+	/* Skip non-running rprocs and the originating instance */
+	if (rproc->state != RPROC_RUNNING || !strcmp(data, sysmon->name)) {
+		dev_dbg(sysmon->dev, "not notifying %s\n", sysmon->name);
+		return NOTIFY_DONE;
+	}
+
+	/* Only SSCTL version 2 supports SSR events */
+	if (sysmon->ssctl_version == 2)
+		ssctl_send_event(sysmon, ssr_name);
+	else if (sysmon->ept)
+		sysmon_send_event(sysmon, ssr_name);
+
+	return NOTIFY_DONE;
+}
+
+/**
+ * qcom_add_sysmon_subdev() - create a sysmon subdev for the given remoteproc
+ * @rproc:	rproc context to associate the subdev with
+ * @name:	name of this subdev, to use in SSR
+ * @ssctl_instance: instance id of the ssctl QMI service
+ *
+ * Return: A new qcom_sysmon object, or NULL on failure
+ */
+struct qcom_sysmon *qcom_add_sysmon_subdev(struct rproc *rproc,
+					   const char *name,
+					   int ssctl_instance)
+{
+	struct qcom_sysmon *sysmon;
+	int ret;
+
+	sysmon = kzalloc(sizeof(*sysmon), GFP_KERNEL);
+	if (!sysmon)
+		return NULL;
+
+	sysmon->dev = rproc->dev.parent;
+	sysmon->rproc = rproc;
+
+	sysmon->name = name;
+	sysmon->ssctl_instance = ssctl_instance;
+
+	init_completion(&sysmon->comp);
+	mutex_init(&sysmon->lock);
+
+	ret = qmi_handle_init(&sysmon->qmi, SSCTL_MAX_MSG_LEN, &ssctl_ops, NULL);
+	if (ret < 0) {
+		dev_err(sysmon->dev, "failed to initialize qmi handle\n");
+		kfree(sysmon);
+		return NULL;
+	}
+
+	qmi_add_lookup(&sysmon->qmi, 43, 0, 0);
+
+	rproc_add_subdev(rproc, &sysmon->subdev, sysmon_start, sysmon_stop);
+
+	sysmon->nb.notifier_call = sysmon_notify;
+	blocking_notifier_chain_register(&sysmon_notifiers, &sysmon->nb);
+
+	mutex_lock(&sysmon_lock);
+	list_add(&sysmon->node, &sysmon_list);
+	mutex_unlock(&sysmon_lock);
+
+	return sysmon;
+}
+EXPORT_SYMBOL_GPL(qcom_add_sysmon_subdev);
+
+/**
+ * qcom_remove_sysmon_subdev() - release a qcom_sysmon
+ * @sysmon:	sysmon context, as retrieved by qcom_add_sysmon_subdev()
+ */
+void qcom_remove_sysmon_subdev(struct qcom_sysmon *sysmon)
+{
+	if (!sysmon)
+		return;
+
+	mutex_lock(&sysmon_lock);
+	list_del(&sysmon->node);
+	mutex_unlock(&sysmon_lock);
+
+	blocking_notifier_chain_unregister(&sysmon_notifiers, &sysmon->nb);
+
+	rproc_remove_subdev(sysmon->rproc, &sysmon->subdev);
+
+	qmi_handle_release(&sysmon->qmi);
+
+	kfree(sysmon);
+}
+EXPORT_SYMBOL_GPL(qcom_remove_sysmon_subdev);
+
+/**
+ * sysmon_probe() - probe sys_mon channel
+ * @rpdev:	rpmsg device handle
+ *
+ * Find the sysmon context associated with the ancestor remoteproc and assign
+ * this rpmsg device with said sysmon context.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+static int sysmon_probe(struct rpmsg_device *rpdev)
+{
+	struct qcom_sysmon *sysmon;
+	struct rproc *rproc;
+
+	rproc = rproc_get_by_child(&rpdev->dev);
+	if (!rproc) {
+		dev_err(&rpdev->dev, "sysmon device not child of rproc\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&sysmon_lock);
+	list_for_each_entry(sysmon, &sysmon_list, node) {
+		if (sysmon->rproc == rproc)
+			goto found;
+	}
+	mutex_unlock(&sysmon_lock);
+
+	dev_err(&rpdev->dev, "no sysmon associated with parent rproc\n");
+
+	return -EINVAL;
+
+found:
+	mutex_unlock(&sysmon_lock);
+
+	rpdev->ept->priv = sysmon;
+	sysmon->ept = rpdev->ept;
+
+	return 0;
+}
+
+/**
+ * sysmon_remove() - sys_mon channel remove handler
+ * @rpdev:	rpmsg device handle
+ *
+ * Disassociate the rpmsg device with the sysmon instance.
+ */
+static void sysmon_remove(struct rpmsg_device *rpdev)
+{
+	struct qcom_sysmon *sysmon = rpdev->ept->priv;
+
+	sysmon->ept = NULL;
+}
+
+static const struct rpmsg_device_id sysmon_match[] = {
+	{ "sys_mon" },
+	{}
+};
+
+static struct rpmsg_driver sysmon_driver = {
+	.probe = sysmon_probe,
+	.remove = sysmon_remove,
+	.callback = sysmon_callback,
+	.id_table = sysmon_match,
+	.drv = {
+		.name = "qcom_sysmon",
+	},
+};
+
+module_rpmsg_driver(sysmon_driver);
+
+MODULE_DESCRIPTION("Qualcomm sysmon driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/remoteproc/qcom_wcnss.c b/drivers/remoteproc/qcom_wcnss.c
index c7686393d505..dc79239c43f9 100644
--- a/drivers/remoteproc/qcom_wcnss.c
+++ b/drivers/remoteproc/qcom_wcnss.c
@@ -40,6 +40,7 @@
 #define WCNSS_CRASH_REASON_SMEM		422
 #define WCNSS_FIRMWARE_NAME		"wcnss.mdt"
 #define WCNSS_PAS_ID			6
+#define WCNSS_SSCTL_ID			0x13
 
 #define WCNSS_SPARE_NVBIN_DLND		BIT(25)
 
@@ -98,6 +99,7 @@ struct qcom_wcnss {
 	size_t mem_size;
 
 	struct qcom_rproc_subdev smd_subdev;
+	struct qcom_sysmon *sysmon;
 };
 
 static const struct wcnss_data riva_data = {
@@ -557,6 +559,7 @@ static int wcnss_probe(struct platform_device *pdev)
 	}
 
 	qcom_add_smd_subdev(rproc, &wcnss->smd_subdev);
+	wcnss->sysmon = qcom_add_sysmon_subdev(rproc, "wcnss", WCNSS_SSCTL_ID);
 
 	ret = rproc_add(rproc);
 	if (ret)
@@ -579,6 +582,7 @@ static int wcnss_remove(struct platform_device *pdev)
 	qcom_smem_state_put(wcnss->state);
 	rproc_del(wcnss->rproc);
 
+	qcom_remove_sysmon_subdev(wcnss->sysmon);
 	qcom_remove_smd_subdev(wcnss->rproc, &wcnss->smd_subdev);
 	rproc_free(wcnss->rproc);
 
-- 
2.15.0