usb: core: add dma-noncoherent buffer alloc and free API

This will add usb_alloc_noncoherent() and usb_free_noncoherent()
functions to support alloc and free buffer in a dma-noncoherent way.

To explicit manage the memory ownership for the kernel and device,
this will also add usb_dma_noncoherent_sync_for_cpu/device() functions
and call it at proper time.  The management requires the user save
sg_table returned by usb_alloc_noncoherent() to urb->sgt.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20250704095751.73765-2-xu.yang_2@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd.c

@@ -1342,29 +1342,35 @@ void usb_hcd_unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
 
 	dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
 	if (IS_ENABLED(CONFIG_HAS_DMA) &&
-	    (urb->transfer_flags & URB_DMA_MAP_SG))
+	    (urb->transfer_flags & URB_DMA_MAP_SG)) {
 		dma_unmap_sg(hcd->self.sysdev,
 				urb->sg,
 				urb->num_sgs,
 				dir);
-	else if (IS_ENABLED(CONFIG_HAS_DMA) &&
-		 (urb->transfer_flags & URB_DMA_MAP_PAGE))
+	} else if (IS_ENABLED(CONFIG_HAS_DMA) &&
+		 (urb->transfer_flags & URB_DMA_MAP_PAGE)) {
 		dma_unmap_page(hcd->self.sysdev,
 				urb->transfer_dma,
 				urb->transfer_buffer_length,
 				dir);
-	else if (IS_ENABLED(CONFIG_HAS_DMA) &&
-		 (urb->transfer_flags & URB_DMA_MAP_SINGLE))
+	} else if (IS_ENABLED(CONFIG_HAS_DMA) &&
+		 (urb->transfer_flags & URB_DMA_MAP_SINGLE)) {
 		dma_unmap_single(hcd->self.sysdev,
 				urb->transfer_dma,
 				urb->transfer_buffer_length,
 				dir);
-	else if (urb->transfer_flags & URB_MAP_LOCAL)
+	} else if (urb->transfer_flags & URB_MAP_LOCAL) {
 		hcd_free_coherent(urb->dev->bus,
 				&urb->transfer_dma,
 				&urb->transfer_buffer,
 				urb->transfer_buffer_length,
 				dir);
+	} else if ((urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP) && urb->sgt) {
+		dma_sync_sgtable_for_cpu(hcd->self.sysdev, urb->sgt, dir);
+		if (dir == DMA_FROM_DEVICE)
+			invalidate_kernel_vmap_range(urb->transfer_buffer,
+						     urb->transfer_buffer_length);
+	}
 
 	/* Make it safe to call this routine more than once */
 	urb->transfer_flags &= ~(URB_DMA_MAP_SG | URB_DMA_MAP_PAGE |
@@ -1425,8 +1431,15 @@ int usb_hcd_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 	}
 
 	dir = usb_urb_dir_in(urb) ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
-	if (urb->transfer_buffer_length != 0
-	    && !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP)) {
+	if (urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP) {
+		if (!urb->sgt)
+			return 0;
+
+		if (dir == DMA_TO_DEVICE)
+			flush_kernel_vmap_range(urb->transfer_buffer,
+						urb->transfer_buffer_length);
+		dma_sync_sgtable_for_device(hcd->self.sysdev, urb->sgt, dir);
+	} else if (urb->transfer_buffer_length != 0) {
 		if (hcd->localmem_pool) {
 			ret = hcd_alloc_coherent(
 					urb->dev->bus, mem_flags,

drivers/usb/core/usb.c

@@ -1030,6 +1030,86 @@ void usb_free_coherent(struct usb_device *dev, size_t size, void *addr,
 }
 EXPORT_SYMBOL_GPL(usb_free_coherent);
 
+/**
+ * usb_alloc_noncoherent - allocate dma-noncoherent buffer for URB_NO_xxx_DMA_MAP
+ * @dev: device the buffer will be used with
+ * @size: requested buffer size
+ * @mem_flags: affect whether allocation may block
+ * @dma: used to return DMA address of buffer
+ * @dir: DMA transfer direction
+ * @table: used to return sg_table of allocated memory
+ *
+ * To explicit manage the memory ownership for the kernel vs the device by
+ * USB core, the user needs save sg_table to urb->sgt. Then USB core will
+ * do DMA sync for CPU and device properly.
+ *
+ * When the buffer is no longer used, free it with usb_free_noncoherent().
+ *
+ * Return: Either null (indicating no buffer could be allocated), or the
+ * cpu-space pointer to a buffer that may be used to perform DMA to the
+ * specified device.  Such cpu-space buffers are returned along with the DMA
+ * address (through the pointer provided).
+ */
+void *usb_alloc_noncoherent(struct usb_device *dev, size_t size,
+			    gfp_t mem_flags, dma_addr_t *dma,
+			    enum dma_data_direction dir,
+			    struct sg_table **table)
+{
+	struct device *dmadev;
+	struct sg_table *sgt;
+	void *buffer;
+
+	if (!dev || !dev->bus)
+		return NULL;
+
+	dmadev = bus_to_hcd(dev->bus)->self.sysdev;
+
+	sgt = dma_alloc_noncontiguous(dmadev, size, dir, mem_flags, 0);
+	if (!sgt)
+		return NULL;
+
+	buffer = dma_vmap_noncontiguous(dmadev, size, sgt);
+	if (!buffer) {
+		dma_free_noncontiguous(dmadev, size, sgt, dir);
+		return NULL;
+	}
+
+	*table = sgt;
+	*dma = sg_dma_address(sgt->sgl);
+
+	return buffer;
+}
+EXPORT_SYMBOL_GPL(usb_alloc_noncoherent);
+
+/**
+ * usb_free_noncoherent - free memory allocated with usb_alloc_noncoherent()
+ * @dev: device the buffer was used with
+ * @size: requested buffer size
+ * @addr: CPU address of buffer
+ * @dir: DMA transfer direction
+ * @table: describe the allocated and DMA mapped memory,
+ *
+ * This reclaims an I/O buffer, letting it be reused.  The memory must have
+ * been allocated using usb_alloc_noncoherent(), and the parameters must match
+ * those provided in that allocation request.
+ */
+void usb_free_noncoherent(struct usb_device *dev, size_t size,
+			  void *addr, enum dma_data_direction dir,
+			  struct sg_table *table)
+{
+	struct device *dmadev;
+
+	if (!dev || !dev->bus)
+		return;
+	if (!addr)
+		return;
+
+	dmadev = bus_to_hcd(dev->bus)->self.sysdev;
+	dma_vunmap_noncontiguous(dmadev, addr);
+	dma_free_noncontiguous(dmadev, size, table, dir);
+}
+EXPORT_SYMBOL_GPL(usb_free_noncoherent);
+
 /*
  * Notifications of device and interface registration
  */

include/linux/usb.h

@@ -1621,6 +1621,7 @@ struct urb {
 	void *transfer_buffer;		/* (in) associated data buffer */
 	dma_addr_t transfer_dma;	/* (in) dma addr for transfer_buffer */
 	struct scatterlist *sg;		/* (in) scatter gather buffer list */
+	struct sg_table *sgt;		/* (in) scatter gather table for noncoherent buffer */
 	int num_mapped_sgs;		/* (internal) mapped sg entries */
 	int num_sgs;			/* (in) number of entries in the sg list */
 	u32 transfer_buffer_length;	/* (in) data buffer length */
@@ -1826,6 +1827,16 @@ void *usb_alloc_coherent(struct usb_device *dev, size_t size,
 void usb_free_coherent(struct usb_device *dev, size_t size,
 	void *addr, dma_addr_t dma);
 
+enum dma_data_direction;
+
+void *usb_alloc_noncoherent(struct usb_device *dev, size_t size,
+			    gfp_t mem_flags, dma_addr_t *dma,
+			    enum dma_data_direction dir,
+			    struct sg_table **table);
+void usb_free_noncoherent(struct usb_device *dev, size_t size,
+			  void *addr, enum dma_data_direction dir,
+			  struct sg_table *table);
+
 /*-------------------------------------------------------------------*
  *                         SYNCHRONOUS CALL SUPPORT                  *
  *-------------------------------------------------------------------*/