1 files changed, 457 insertions, 0 deletions
diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
new file mode 100644
index 000000000000..d49f9886dd84
--- /dev/null
+++ b/drivers/usb/host/xhci-sideband.c
@@ -0,0 +1,457 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * xHCI host controller sideband support
+ *
+ * Copyright (c) 2023-2025, Intel Corporation.
+ *
+ * Author: Mathias Nyman
+ */
+
+#include <linux/usb/xhci-sideband.h>
+#include <linux/dma-direct.h>
+
+#include "xhci.h"
+
+/* sideband internal helpers */
+static struct sg_table *
+xhci_ring_to_sgtable(struct xhci_sideband *sb, struct xhci_ring *ring)
+{
+	struct xhci_segment *seg;
+	struct sg_table	*sgt;
+	unsigned int n_pages;
+	struct page **pages;
+	struct device *dev;
+	size_t sz;
+	int i;
+
+	dev = xhci_to_hcd(sb->xhci)->self.sysdev;
+	sz = ring->num_segs * TRB_SEGMENT_SIZE;
+	n_pages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+	pages = kvmalloc_array(n_pages, sizeof(struct page *), GFP_KERNEL);
+	if (!pages)
+		return NULL;
+
+	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
+	if (!sgt) {
+		kvfree(pages);
+		return NULL;
+	}
+
+	seg = ring->first_seg;
+	if (!seg)
+		goto err;
+	/*
+	 * Rings can potentially have multiple segments, create an array that
+	 * carries page references to allocated segments.  Utilize the
+	 * sg_alloc_table_from_pages() to create the sg table, and to ensure
+	 * that page links are created.
+	 */
+	for (i = 0; i < ring->num_segs; i++) {
+		dma_get_sgtable(dev, sgt, seg->trbs, seg->dma,
+				TRB_SEGMENT_SIZE);
+		pages[i] = sg_page(sgt->sgl);
+		sg_free_table(sgt);
+		seg = seg->next;
+	}
+
+	if (sg_alloc_table_from_pages(sgt, pages, n_pages, 0, sz, GFP_KERNEL))
+		goto err;
+
+	/*
+	 * Save first segment dma address to sg dma_address field for the sideband
+	 * client to have access to the IOVA of the ring.
+	 */
+	sg_dma_address(sgt->sgl) = ring->first_seg->dma;
+
+	return sgt;
+
+err:
+	kvfree(pages);
+	kfree(sgt);
+
+	return NULL;
+}
+
+static void
+__xhci_sideband_remove_endpoint(struct xhci_sideband *sb, struct xhci_virt_ep *ep)
+{
+	/*
+	 * Issue a stop endpoint command when an endpoint is removed.
+	 * The stop ep cmd handler will handle the ring cleanup.
+	 */
+	xhci_stop_endpoint_sync(sb->xhci, ep, 0, GFP_KERNEL);
+
+	ep->sideband = NULL;
+	sb->eps[ep->ep_index] = NULL;
+}
+
+/* sideband api functions */
+
+/**
+ * xhci_sideband_notify_ep_ring_free - notify client of xfer ring free
+ * @sb: sideband instance for this usb device
+ * @ep_index: usb endpoint index
+ *
+ * Notifies the xHCI sideband client driver of a xHCI transfer ring free
+ * routine.  This will allow for the client to ensure that all transfers
+ * are completed.
+ *
+ * The callback should be synchronous, as the ring free happens after.
+ */
+void xhci_sideband_notify_ep_ring_free(struct xhci_sideband *sb,
+				       unsigned int ep_index)
+{
+	struct xhci_sideband_event evt;
+
+	evt.type = XHCI_SIDEBAND_XFER_RING_FREE;
+	evt.evt_data = &ep_index;
+
+	if (sb->notify_client)
+		sb->notify_client(sb->intf, &evt);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_notify_ep_ring_free);
+
+/**
+ * xhci_sideband_add_endpoint - add endpoint to sideband access list
+ * @sb: sideband instance for this usb device
+ * @host_ep: usb host endpoint
+ *
+ * Adds an endpoint to the list of sideband accessed endpoints for this usb
+ * device.
+ * After an endpoint is added the sideband client can get the endpoint transfer
+ * ring buffer by calling xhci_sideband_endpoint_buffer()
+ *
+ * Return: 0 on success, negative error otherwise.
+ */
+int
+xhci_sideband_add_endpoint(struct xhci_sideband *sb,
+			   struct usb_host_endpoint *host_ep)
+{
+	struct xhci_virt_ep *ep;
+	unsigned int ep_index;
+
+	mutex_lock(&sb->mutex);
+	ep_index = xhci_get_endpoint_index(&host_ep->desc);
+	ep = &sb->vdev->eps[ep_index];
+
+	if (ep->ep_state & EP_HAS_STREAMS) {
+		mutex_unlock(&sb->mutex);
+		return -EINVAL;
+	}
+
+	/*
+	 * Note, we don't know the DMA mask of the audio DSP device, if its
+	 * smaller than for xhci it won't be able to access the endpoint ring
+	 * buffer. This could be solved by not allowing the audio class driver
+	 * to add the endpoint the normal way, but instead offload it immediately,
+	 * and let this function add the endpoint and allocate the ring buffer
+	 * with the smallest common DMA mask
+	 */
+	if (sb->eps[ep_index] || ep->sideband) {
+		mutex_unlock(&sb->mutex);
+		return -EBUSY;
+	}
+
+	ep->sideband = sb;
+	sb->eps[ep_index] = ep;
+	mutex_unlock(&sb->mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_add_endpoint);
+
+/**
+ * xhci_sideband_remove_endpoint - remove endpoint from sideband access list
+ * @sb: sideband instance for this usb device
+ * @host_ep: usb host endpoint
+ *
+ * Removes an endpoint from the list of sideband accessed endpoints for this usb
+ * device.
+ * sideband client should no longer touch the endpoint transfer buffer after
+ * calling this.
+ *
+ * Return: 0 on success, negative error otherwise.
+ */
+int
+xhci_sideband_remove_endpoint(struct xhci_sideband *sb,
+			      struct usb_host_endpoint *host_ep)
+{
+	struct xhci_virt_ep *ep;
+	unsigned int ep_index;
+
+	mutex_lock(&sb->mutex);
+	ep_index = xhci_get_endpoint_index(&host_ep->desc);
+	ep = sb->eps[ep_index];
+
+	if (!ep || !ep->sideband || ep->sideband != sb) {
+		mutex_unlock(&sb->mutex);
+		return -ENODEV;
+	}
+
+	__xhci_sideband_remove_endpoint(sb, ep);
+	xhci_initialize_ring_info(ep->ring);
+	mutex_unlock(&sb->mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_remove_endpoint);
+
+int
+xhci_sideband_stop_endpoint(struct xhci_sideband *sb,
+			    struct usb_host_endpoint *host_ep)
+{
+	struct xhci_virt_ep *ep;
+	unsigned int ep_index;
+
+	ep_index = xhci_get_endpoint_index(&host_ep->desc);
+	ep = sb->eps[ep_index];
+
+	if (!ep || !ep->sideband || ep->sideband != sb)
+		return -EINVAL;
+
+	return xhci_stop_endpoint_sync(sb->xhci, ep, 0, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_stop_endpoint);
+
+/**
+ * xhci_sideband_get_endpoint_buffer - gets the endpoint transfer buffer address
+ * @sb: sideband instance for this usb device
+ * @host_ep: usb host endpoint
+ *
+ * Returns the address of the endpoint buffer where xHC controller reads queued
+ * transfer TRBs from. This is the starting address of the ringbuffer where the
+ * sideband client should write TRBs to.
+ *
+ * Caller needs to free the returned sg_table
+ *
+ * Return: struct sg_table * if successful. NULL otherwise.
+ */
+struct sg_table *
+xhci_sideband_get_endpoint_buffer(struct xhci_sideband *sb,
+				  struct usb_host_endpoint *host_ep)
+{
+	struct xhci_virt_ep *ep;
+	unsigned int ep_index;
+
+	ep_index = xhci_get_endpoint_index(&host_ep->desc);
+	ep = sb->eps[ep_index];
+
+	if (!ep || !ep->ring || !ep->sideband || ep->sideband != sb)
+		return NULL;
+
+	return xhci_ring_to_sgtable(sb, ep->ring);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_get_endpoint_buffer);
+
+/**
+ * xhci_sideband_get_event_buffer - return the event buffer for this device
+ * @sb: sideband instance for this usb device
+ *
+ * If a secondary xhci interupter is set up for this usb device then this
+ * function returns the address of the event buffer where xHC writes
+ * the transfer completion events.
+ *
+ * Caller needs to free the returned sg_table
+ *
+ * Return: struct sg_table * if successful. NULL otherwise.
+ */
+struct sg_table *
+xhci_sideband_get_event_buffer(struct xhci_sideband *sb)
+{
+	if (!sb || !sb->ir)
+		return NULL;
+
+	return xhci_ring_to_sgtable(sb, sb->ir->event_ring);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_get_event_buffer);
+
+/**
+ * xhci_sideband_create_interrupter - creates a new interrupter for this sideband
+ * @sb: sideband instance for this usb device
+ * @num_seg: number of event ring segments to allocate
+ * @ip_autoclear: IP autoclearing support such as MSI implemented
+ *
+ * Sets up a xhci interrupter that can be used for this sideband accessed usb
+ * device. Transfer events for this device can be routed to this interrupters
+ * event ring by setting the 'Interrupter Target' field correctly when queueing
+ * the transfer TRBs.
+ * Once this interrupter is created the interrupter target ID can be obtained
+ * by calling xhci_sideband_interrupter_id()
+ *
+ * Returns 0 on success, negative error otherwise
+ */
+int
+xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
+				 bool ip_autoclear, u32 imod_interval, int intr_num)
+{
+	int ret = 0;
+
+	if (!sb || !sb->xhci)
+		return -ENODEV;
+
+	mutex_lock(&sb->mutex);
+	if (sb->ir) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	sb->ir = xhci_create_secondary_interrupter(xhci_to_hcd(sb->xhci),
+						   num_seg, imod_interval,
+						   intr_num);
+	if (!sb->ir) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	sb->ir->ip_autoclear = ip_autoclear;
+
+out:
+	mutex_unlock(&sb->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_create_interrupter);
+
+/**
+ * xhci_sideband_remove_interrupter - remove the interrupter from a sideband
+ * @sb: sideband instance for this usb device
+ *
+ * Removes a registered interrupt for a sideband.  This would allow for other
+ * sideband users to utilize this interrupter.
+ */
+void
+xhci_sideband_remove_interrupter(struct xhci_sideband *sb)
+{
+	if (!sb || !sb->ir)
+		return;
+
+	mutex_lock(&sb->mutex);
+	xhci_remove_secondary_interrupter(xhci_to_hcd(sb->xhci), sb->ir);
+
+	sb->ir = NULL;
+	mutex_unlock(&sb->mutex);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_remove_interrupter);
+
+/**
+ * xhci_sideband_interrupter_id - return the interrupter target id
+ * @sb: sideband instance for this usb device
+ *
+ * If a secondary xhci interrupter is set up for this usb device then this
+ * function returns the ID used by the interrupter. The sideband client
+ * needs to write this ID to the 'Interrupter Target' field of the transfer TRBs
+ * it queues on the endpoints transfer ring to ensure transfer completion event
+ * are written by xHC to the correct interrupter event ring.
+ *
+ * Returns interrupter id on success, negative error othgerwise
+ */
+int
+xhci_sideband_interrupter_id(struct xhci_sideband *sb)
+{
+	if (!sb || !sb->ir)
+		return -ENODEV;
+
+	return sb->ir->intr_num;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_interrupter_id);
+
+/**
+ * xhci_sideband_register - register a sideband for a usb device
+ * @intf: usb interface associated with the sideband device
+ *
+ * Allows for clients to utilize XHCI interrupters and fetch transfer and event
+ * ring parameters for executing data transfers.
+ *
+ * Return: pointer to a new xhci_sideband instance if successful. NULL otherwise.
+ */
+struct xhci_sideband *
+xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type,
+		       int (*notify_client)(struct usb_interface *intf,
+				    struct xhci_sideband_event *evt))
+{
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
+	struct xhci_virt_device *vdev;
+	struct xhci_sideband *sb;
+
+	/*
+	 * Make sure the usb device is connected to a xhci controller.  Fail
+	 * registration if the type is anything other than  XHCI_SIDEBAND_VENDOR,
+	 * as this is the only type that is currently supported by xhci-sideband.
+	 */
+	if (!udev->slot_id || type != XHCI_SIDEBAND_VENDOR)
+		return NULL;
+
+	sb = kzalloc_node(sizeof(*sb), GFP_KERNEL, dev_to_node(hcd->self.sysdev));
+	if (!sb)
+		return NULL;
+
+	mutex_init(&sb->mutex);
+
+	/* check this device isn't already controlled via sideband */
+	spin_lock_irq(&xhci->lock);
+
+	vdev = xhci->devs[udev->slot_id];
+
+	if (!vdev || vdev->sideband) {
+		xhci_warn(xhci, "XHCI sideband for slot %d already in use\n",
+			  udev->slot_id);
+		spin_unlock_irq(&xhci->lock);
+		kfree(sb);
+		return NULL;
+	}
+
+	sb->xhci = xhci;
+	sb->vdev = vdev;
+	sb->intf = intf;
+	sb->type = type;
+	sb->notify_client = notify_client;
+	vdev->sideband = sb;
+
+	spin_unlock_irq(&xhci->lock);
+
+	return sb;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_register);
+
+/**
+ * xhci_sideband_unregister - unregister sideband access to a usb device
+ * @sb: sideband instance to be unregistered
+ *
+ * Unregisters sideband access to a usb device and frees the sideband
+ * instance.
+ * After this the endpoint and interrupter event buffers should no longer
+ * be accessed via sideband. The xhci driver can now take over handling
+ * the buffers.
+ */
+void
+xhci_sideband_unregister(struct xhci_sideband *sb)
+{
+	struct xhci_hcd *xhci;
+	int i;
+
+	if (!sb)
+		return;
+
+	xhci = sb->xhci;
+
+	mutex_lock(&sb->mutex);
+	for (i = 0; i < EP_CTX_PER_DEV; i++)
+		if (sb->eps[i])
+			__xhci_sideband_remove_endpoint(sb, sb->eps[i]);
+	mutex_unlock(&sb->mutex);
+
+	xhci_sideband_remove_interrupter(sb);
+
+	spin_lock_irq(&xhci->lock);
+	sb->xhci = NULL;
+	sb->vdev->sideband = NULL;
+	spin_unlock_irq(&xhci->lock);
+
+	kfree(sb);
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_unregister);
+MODULE_DESCRIPTION("xHCI sideband driver for secondary interrupter management");
+MODULE_LICENSE("GPL");