firmware: arm_scmi: virtio: Rework transport probe sequence

Use the new per-instance transport handles helpers to synchronize and
optionally defer the core SCMI driver probe up until the transport driver
has completely been initialized and it is fully operational as a supplier.

Introduce proper module init/exit routines while removing the ugly trick of
registering a driver from within the probe sequence of another one, just to
avoid to have to deal with probe deferrals.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://patch.msgid.link/20260510160527.3537474-4-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

diff --git a/drivers/firmware/arm_scmi/transports/virtio.c b/drivers/firmware/arm_scmi/transports/virtio.c
index 326c4a93e44b91099a5fd8cb441da78e7af3078f..3282d8271839df8579fc11e97df65c8d87b09666 100644 (file)
--- a/drivers/firmware/arm_scmi/transports/virtio.c
+++ b/drivers/firmware/arm_scmi/transports/virtio.c
@@ -4,7 +4,7 @@
  * (SCMI).
  *
  * Copyright (C) 2020-2022 OpenSynergy.
- * Copyright (C) 2021-2024 ARM Ltd.
+ * Copyright (C) 2021-2026 ARM Ltd.
  */
 
 /**
@@ -116,6 +116,8 @@ static struct scmi_transport_core_operations *core;
 /* Only one SCMI VirtIO device can possibly exist */
 static struct virtio_device *scmi_vdev;
 
+static DEFINE_SCMI_TRANSPORT_SUPPLIER(scmi_virtio_supplier);
+
 static void scmi_vio_channel_ready(struct scmi_vio_channel *vioch,
                                   struct scmi_chan_info *cinfo)
 {
@@ -394,6 +396,10 @@ static bool virtio_chan_available(struct device_node *of_node, int idx)
                return false;
        }
 
+       dev_dbg(&scmi_vdev->dev, "%s Channel %sAVAILABLE on SCMI Virtio device.\n",
+               idx == VIRTIO_SCMI_VQ_TX ? "TX" : "RX",
+               (vioch && !vioch->cinfo) ? "" : "NOT ");
+
        return vioch && !vioch->cinfo;
 }
 
@@ -410,7 +416,7 @@ static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
        int i;
 
        if (!scmi_vdev)
-               return -EPROBE_DEFER;
+               return -EINVAL;
 
        vioch = &((struct scmi_vio_channel *)scmi_vdev->priv)[index];
 
@@ -460,6 +466,9 @@ static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
 
        scmi_vio_channel_ready(vioch, cinfo);
 
+       dev_dbg(&scmi_vdev->dev, "%s Channel SETUP on SCMI Virtio device.\n",
+               tx ? "TX" : "RX");
+
        return 0;
 }
 
@@ -801,7 +810,7 @@ static struct scmi_desc scmi_virtio_desc = {
 };
 
 static const struct of_device_id scmi_of_match[] = {
-       { .compatible = "arm,scmi-virtio" },
+       { .compatible = "arm,scmi-virtio", .data = &scmi_virtio_supplier.th},
        { /* Sentinel */ },
 };
 
@@ -864,33 +873,33 @@ static int scmi_vio_probe(struct virtio_device *vdev)
                        sz = MSG_TOKEN_MAX;
                }
                channels[i].max_msg = sz;
+               dev_dbg(dev, "VQ%d initialized with max_msg: %d\n", i, sz);
        }
 
        vdev->priv = channels;
-
        /* Ensure initialized scmi_vdev is visible */
        smp_store_mb(scmi_vdev, vdev);
 
        /* Set device ready */
        virtio_device_ready(vdev);
 
-       ret = platform_driver_register(&scmi_virtio_driver);
+       ret = scmi_transport_supplier_put(&scmi_virtio_supplier.th, &vdev->dev);
        if (ret) {
+               virtio_reset_device(vdev);
                vdev->priv = NULL;
                vdev->config->del_vqs(vdev);
                /* Ensure NULLified scmi_vdev is visible */
                smp_store_mb(scmi_vdev, NULL);
-
                return ret;
        }
 
+       dev_dbg(dev, "Probed and initialized SCMI Virtio device.\n");
+
        return 0;
 }
 
 static void scmi_vio_remove(struct virtio_device *vdev)
 {
-       platform_driver_unregister(&scmi_virtio_driver);
-
        /*
         * Once we get here, virtio_chan_free() will have already been called by
         * the SCMI core for any existing channel and, as a consequence, all the
@@ -900,8 +909,10 @@ static void scmi_vio_remove(struct virtio_device *vdev)
         */
        virtio_reset_device(vdev);
        vdev->config->del_vqs(vdev);
+
        /* Ensure scmi_vdev is visible as NULL */
        smp_store_mb(scmi_vdev, NULL);
+       scmi_transport_supplier_put(&scmi_virtio_supplier.th, &vdev->dev);
 }
 
 static int scmi_vio_validate(struct virtio_device *vdev)
@@ -936,7 +947,30 @@ static struct virtio_driver virtio_scmi_driver = {
        .validate = scmi_vio_validate,
 };
 
-module_virtio_driver(virtio_scmi_driver);
+static int __init scmi_transport_virtio_init(void)
+{
+       int ret;
+
+       ret = register_virtio_driver(&virtio_scmi_driver);
+       if (ret)
+               return ret;
+
+       ret = platform_driver_register(&scmi_virtio_driver);
+       if (ret) {
+               unregister_virtio_driver(&virtio_scmi_driver);
+               return ret;
+       }
+
+       return ret;
+}
+module_init(scmi_transport_virtio_init);
+
+static void __exit scmi_transport_virtio_exit(void)
+{
+       platform_driver_unregister(&scmi_virtio_driver);
+       unregister_virtio_driver(&virtio_scmi_driver);
+}
+module_exit(scmi_transport_virtio_exit);
 
 MODULE_AUTHOR("Igor Skalkin <igor.skalkin@opensynergy.com>");
 MODULE_AUTHOR("Peter Hilber <peter.hilber@opensynergy.com>");