[RFC PATCH v4 12/14] coco: host: arm64: Refcount root-port pdevs used by IDE streams

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

Keep the root-port RMM pdev alive while endpoint IDE streams are attached
to it.

Add a kref to the root-port descriptor, take a reference when reusing an
existing root-port pdev for stream setup, and drop it when the endpoint
disconnects. Release the root-port pdev once the final reference is
dropped, tearing down the RMM object and its communication buffers at that
point.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 drivers/virt/coco/arm-cca-host/arm-cca.c | 31 +++++++++++++++++++++---
 drivers/virt/coco/arm-cca-host/rmi-da.h  |  4 +++
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/drivers/virt/coco/arm-cca-host/arm-cca.c b/drivers/virt/coco/arm-cca-host/arm-cca.c
index de7a2e156549..0b1200f591ab 100644
--- a/drivers/virt/coco/arm-cca-host/arm-cca.c
+++ b/drivers/virt/coco/arm-cca-host/arm-cca.c
@@ -134,6 +134,23 @@ static int alloc_stream_id(struct pci_host_bridge *hb)
 	return stream_id;
 }
 
+static void cca_root_port_pdev_release(struct kref *kref)
+{
+	struct cca_host_rp_dsc *rp_dsc = container_of(kref, struct cca_host_rp_dsc,
+						      tsm_ref);
+	struct pci_dev *rp = rp_dsc->pci.pdev;
+
+	cca_pdev_stop_and_destroy(rp);
+	free_dev_communication_buffers(&rp_dsc->pdev.comm_data);
+	rp->tsm = NULL;
+	kfree(rp_dsc);
+}
+
+static inline void cca_root_port_pdev_put(struct cca_host_rp_dsc *rp_dsc)
+{
+	kref_put(&rp_dsc->tsm_ref, cca_root_port_pdev_release);
+}
+
 static int cca_root_port_pdev_create(struct pci_dev *rp, struct tsm_dev *tsm_dev)
 {
 	int ret;
@@ -151,6 +168,7 @@ static int cca_root_port_pdev_create(struct pci_dev *rp, struct tsm_dev *tsm_dev
 	rp->tsm->dsm_dev = rp;
 	rp->tsm->pdev = rp;
 	rp->tsm->tsm_dev = tsm_dev;
+	kref_init(&rp_dsc->tsm_ref);
 	mutex_init(&rp_dsc->pdev.object_lock);
 
 	ret = init_dev_communication_buffers(rp, &rp_dsc->pdev.comm_data);
@@ -222,12 +240,15 @@ static int cca_pdev_create_ncoh_stream(struct pci_dev *pdev, unsigned long strea
 		/* Make sure they use the same TSM */
 		if (rp->tsm->tsm_dev != pf0_ep_dsc->pci.base_tsm.tsm_dev)
 			return -EINVAL;
-	}
 
+		kref_get(&rp_dsc->tsm_ref);
+	}
 
 	params = (struct rmi_pdev_stream_params *)get_zeroed_page(GFP_KERNEL);
-	if (!params)
+	if (!params) {
+		cca_root_port_pdev_put(rp_dsc);
 		return -ENOMEM;
+	}
 
 	params->flags = 0;
 	params->type = RMI_PDEV_STREAM_NCOH;
@@ -237,7 +258,9 @@ static int cca_pdev_create_ncoh_stream(struct pci_dev *pdev, unsigned long strea
 	params->num_addr_range = pci_dev_addr_range(pdev, params->addr_range);
 
 	ret = cca_pdev_stream_connect(pdev, rp, params, &stream_handle);
-	if (!ret)
+	if (ret)
+		cca_root_port_pdev_put(rp_dsc);
+	else
 		pf0_ep_dsc->stream_handle = stream_handle;
 
 	free_page((unsigned long)params);
@@ -375,6 +398,8 @@ static void cca_tsm_disconnect(struct pci_dev *pdev)
 	}
 
 	cca_pdev_disconnect_stream(pdev, rp, pf0_ep_dsc->stream_handle);
+	if (rp)
+		cca_root_port_pdev_put(to_cca_rp_dsc(rp));
 
 	cca_pdev_stop_and_destroy(pdev);
 	free_dev_communication_buffers(&pf0_ep_dsc->pdev.comm_data);
diff --git a/drivers/virt/coco/arm-cca-host/rmi-da.h b/drivers/virt/coco/arm-cca-host/rmi-da.h
index ea5f7df3541f..798a8ed7505f 100644
--- a/drivers/virt/coco/arm-cca-host/rmi-da.h
+++ b/drivers/virt/coco/arm-cca-host/rmi-da.h
@@ -10,6 +10,9 @@
 #include <linux/pci-ide.h>
 #include <linux/pci-tsm.h>
 #include <linux/sizes.h>
+#include <linux/atomic.h>
+#include <linux/kref.h>
+#include <linux/wait.h>
 #include <asm/rmi_cmds.h>
 #include <asm/rmi_smc.h>
 
@@ -104,6 +107,7 @@ struct cca_host_pf0_ep_dsc {
 struct cca_host_rp_dsc {
 	struct pci_tsm pci;
 	struct cca_host_pdev_dsc pdev;
+	struct kref tsm_ref;
 };
 
 struct cca_host_fn_dsc {
-- 
2.43.0