soc: qcom: apr: Add avs/audio tracking functionality

Use PDR helper functions to track the protection domains that the apr
services are dependent upon on SDM845 SoC, specifically the "avs/audio"
service running on ADSP Q6.

Reviewed-by: Bjorn Andersson <[e-mail]>
Signed-off-by: Sibi Sankar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bjorn Andersson <[e-mail]>

drivers/soc/qcom/Kconfig

···
 	tristate "Qualcomm APR Bus (Asynchronous Packet Router)"
 	depends on ARCH_QCOM || COMPILE_TEST
 	depends on RPMSG
+	select QCOM_PDR_HELPERS
 	help
 	  Enable APR IPC protocol support between
 	  application processor and QDSP6. APR is

drivers/soc/qcom/apr.c

···
 #include <linux/workqueue.h>
 #include <linux/of_device.h>
 #include <linux/soc/qcom/apr.h>
+#include <linux/soc/qcom/pdr.h>
 #include <linux/rpmsg.h>
 #include <linux/of.h>
 
···
 	spinlock_t rx_lock;
 	struct idr svcs_idr;
 	int dest_domain_id;
+	struct pdr_handle *pdr;
 	struct workqueue_struct *rxwq;
 	struct work_struct rx_work;
 	struct list_head rx_list;
···
 		  id->svc_id + 1, GFP_ATOMIC);
 	spin_unlock(&apr->svcs_lock);
 
+	of_property_read_string_index(np, "qcom,protection-domain",
+				      1, &adev->service_path);
+
 	dev_info(dev, "Adding APR dev: %s\n", dev_name(&adev->dev));
 
 	ret = device_register(&adev->dev);
···
 	return ret;
 }
 
-static void of_register_apr_devices(struct device *dev)
+static int of_apr_add_pd_lookups(struct device *dev)
+{
+	const char *service_name, *service_path;
+	struct apr *apr = dev_get_drvdata(dev);
+	struct device_node *node;
+	struct pdr_service *pds;
+	int ret;
+
+	for_each_child_of_node(dev->of_node, node) {
+		ret = of_property_read_string_index(node, "qcom,protection-domain",
+						    0, &service_name);
+		if (ret < 0)
+			continue;
+
+		ret = of_property_read_string_index(node, "qcom,protection-domain",
+						    1, &service_path);
+		if (ret < 0) {
+			dev_err(dev, "pdr service path missing: %d\n", ret);
+			return ret;
+		}
+
+		pds = pdr_add_lookup(apr->pdr, service_name, service_path);
+		if (IS_ERR(pds) && PTR_ERR(pds) != -EALREADY) {
+			dev_err(dev, "pdr add lookup failed: %d\n", ret);
+			return PTR_ERR(pds);
+		}
+	}
+
+	return 0;
+}
+
+static void of_register_apr_devices(struct device *dev, const char *svc_path)
 {
 	struct apr *apr = dev_get_drvdata(dev);
 	struct device_node *node;
+	const char *service_path;
+	int ret;
 
 	for_each_child_of_node(dev->of_node, node) {
 		struct apr_device_id id = { {0} };
+
+		/*
+		 * This function is called with svc_path NULL during
+		 * apr_probe(), in which case we register any apr devices
+		 * without a qcom,protection-domain specified.
+		 *
+		 * Then as the protection domains becomes available
+		 * (if applicable) this function is again called, but with
+		 * svc_path representing the service becoming available. In
+		 * this case we register any apr devices with a matching
+		 * qcom,protection-domain.
+		 */
+
+		ret = of_property_read_string_index(node, "qcom,protection-domain",
+						    1, &service_path);
+		if (svc_path) {
+			/* skip APR services that are PD independent */
+			if (ret)
+				continue;
+
+			/* skip APR services whose PD paths don't match */
+			if (strcmp(service_path, svc_path))
+				continue;
+		} else {
+			/* skip APR services whose PD lookups are registered */
+			if (ret == 0)
+				continue;
+		}
 
 		if (of_property_read_u32(node, "reg", &id.svc_id))
 			continue;
···
 
 		if (apr_add_device(dev, node, &id))
 			dev_err(dev, "Failed to add apr %d svc\n", id.svc_id);
+	}
+}
+
+static int apr_remove_device(struct device *dev, void *svc_path)
+{
+	struct apr_device *adev = to_apr_device(dev);
+
+	if (svc_path && adev->service_path) {
+		if (!strcmp(adev->service_path, (char *)svc_path))
+			device_unregister(&adev->dev);
+	} else {
+		device_unregister(&adev->dev);
+	}
+
+	return 0;
+}
+
+static void apr_pd_status(int state, char *svc_path, void *priv)
+{
+	struct apr *apr = (struct apr *)priv;
+
+	switch (state) {
+	case SERVREG_SERVICE_STATE_UP:
+		of_register_apr_devices(apr->dev, svc_path);
+		break;
+	case SERVREG_SERVICE_STATE_DOWN:
+		device_for_each_child(apr->dev, svc_path, apr_remove_device);
+		break;
 	}
 }
 
···
 		return -ENOMEM;
 	}
 	INIT_WORK(&apr->rx_work, apr_rxwq);
+
+	apr->pdr = pdr_handle_alloc(apr_pd_status, apr);
+	if (IS_ERR(apr->pdr)) {
+		dev_err(dev, "Failed to init PDR handle\n");
+		ret = PTR_ERR(apr->pdr);
+		goto destroy_wq;
+	}
+
 	INIT_LIST_HEAD(&apr->rx_list);
 	spin_lock_init(&apr->rx_lock);
 	spin_lock_init(&apr->svcs_lock);
 	idr_init(&apr->svcs_idr);
-	of_register_apr_devices(dev);
+
+	ret = of_apr_add_pd_lookups(dev);
+	if (ret)
+		goto handle_release;
+
+	of_register_apr_devices(dev, NULL);
 
 	return 0;
-}
 
-static int apr_remove_device(struct device *dev, void *null)
-{
-	struct apr_device *adev = to_apr_device(dev);
-
-	device_unregister(&adev->dev);
-
-	return 0;
+handle_release:
+	pdr_handle_release(apr->pdr);
+destroy_wq:
+	destroy_workqueue(apr->rxwq);
+	return ret;
 }
 
 static void apr_remove(struct rpmsg_device *rpdev)
 {
 	struct apr *apr = dev_get_drvdata(&rpdev->dev);
 
+	pdr_handle_release(apr->pdr);
 	device_for_each_child(&rpdev->dev, NULL, apr_remove_device);
 	flush_workqueue(apr->rxwq);
 	destroy_workqueue(apr->rxwq);

include/linux/soc/qcom/apr.h

···
 	uint16_t	domain_id;
 	uint32_t	version;
 	char name[APR_NAME_SIZE];
+	const char *service_path;
 	spinlock_t	lock;
 	struct list_head node;
 };