[PATCH v3 1/3] usb: core: add dma-noncoherent buffer alloc and free API

[Xu Yang <xu.yang_2@nxp.com>]

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>

---
Changes in v3:
 - put Return section at the end of description
 - correct some abbreviations
 - remove usb_dma_noncoherent_sync_for_cpu() and
   usb_dma_noncoherent_sync_for_device()
 - do DMA sync in usb_hcd_map_urb_for_dma() and
   usb_hcd_unmap_urb_for_dma()
 - call flush_kernel_vmap_range() for OUT transfers
   and invalidate_kernel_vmap_range() for IN transfers
---
 drivers/usb/core/hcd.c | 19 ++++++++++
 drivers/usb/core/usb.c | 80 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/usb.h    | 11 ++++++
 3 files changed, 110 insertions(+)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index c22de97432a0..e0fa6d6d273b 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1366,6 +1366,14 @@ void usb_hcd_unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
 				urb->transfer_buffer_length,
 				dir);
 
+	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 |
 			URB_DMA_MAP_SINGLE | URB_MAP_LOCAL);
@@ -1491,7 +1499,18 @@ int usb_hcd_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
 		if (ret && (urb->transfer_flags & (URB_SETUP_MAP_SINGLE |
 				URB_SETUP_MAP_LOCAL)))
 			usb_hcd_unmap_urb_for_dma(hcd, urb);
+
+		return ret;
 	}
+
+	if ((urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP) &&
+	    urb->sgt) {
+		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);
+	}
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(usb_hcd_map_urb_for_dma);
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 118fa4c93a79..fca7735fc660 100644
--- a/drivers/usb/core/usb.c
+++ b/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
  */
diff --git a/include/linux/usb.h b/include/linux/usb.h
index e8662843e68c..9ade441ab4c8 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1619,6 +1619,7 @@ 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 */
@@ -1824,6 +1825,16 @@ 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                  *
  *-------------------------------------------------------------------*/
-- 
2.34.1