If these are not met use a bounce buffer.
This is done by adding a member dma_align_shift to
struct hc_driver. Defaulting to zero causes unmodified
HCDs to be assumed to be byte aligned DMA capable.
Signed-off-by: Martin Fuzzey <mfuzzey@xxxxxxxxx>
---
drivers/usb/core/hcd.c | 54 +++++++++++++++++++++++++++++++++++++----------
include/linux/usb.h | 1 +
include/linux/usb/hcd.h | 2 ++
3 files changed, 45 insertions(+), 12 deletions(-)
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 12742f1..8ad9367 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1286,12 +1286,19 @@ static void unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
urb->transfer_dma,
urb->transfer_buffer_length,
dir);
- else if (urb->transfer_flags & URB_DMA_MAP_SINGLE)
+ else if (urb->transfer_flags & URB_DMA_MAP_SINGLE) {
dma_unmap_single(hcd->self.controller,
urb->transfer_dma,
urb->transfer_buffer_length,
dir);
- else if (urb->transfer_flags & URB_MAP_LOCAL)
+ if (urb->bounce_buffer) {
+ if (dir == DMA_FROM_DEVICE)
+ memcpy(urb->transfer_buffer,
+ urb->bounce_buffer,
+ urb->transfer_buffer_length);
+ kfree(urb->bounce_buffer);
+ }
+ } else if (urb->transfer_flags & URB_MAP_LOCAL)
hcd_free_coherent(urb->dev->bus,
&urb->transfer_dma,
&urb->transfer_buffer,
@@ -1373,16 +1380,39 @@ static int map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
else
urb->transfer_flags |= URB_DMA_MAP_PAGE;
} else {
- urb->transfer_dma = dma_map_single(
- hcd->self.controller,
- urb->transfer_buffer,
- urb->transfer_buffer_length,
- dir);
- if (dma_mapping_error(hcd->self.controller,
- urb->transfer_dma))
- ret = -EAGAIN;
- else
- urb->transfer_flags |= URB_DMA_MAP_SINGLE;
+ void *buffer = urb->transfer_buffer;
+
+ if (IS_ALIGNED((unsigned long)buffer,
+ 1 << hcd->driver->dma_align_shift))
+ urb->bounce_buffer = NULL;
+ else {
+ if (dir == DMA_TO_DEVICE)
+ buffer = kmemdup(
+ buffer,
+ urb->transfer_buffer_length,
+ mem_flags);
+ else
+ buffer = kmalloc(
+ urb->transfer_buffer_length,
+ mem_flags);
+
+ if (!buffer)
+ ret = -ENOMEM;
+ urb->bounce_buffer = buffer;
+ }
+
+ if (buffer) {
+ urb->transfer_dma = dma_map_single(
+ hcd->self.controller,
+ buffer,
+ urb->transfer_buffer_length,
+ dir);
+ if (dma_mapping_error(hcd->self.controller,
+ urb->transfer_dma))
+ ret = -EAGAIN;
+ else
+ urb->transfer_flags |= URB_DMA_MAP_SINGLE;
+ }
}
} else if (hcd->driver->flags & HCD_LOCAL_MEM) {
ret = hcd_alloc_coherent(
diff --git a/include/linux/usb.h b/include/linux/usb.h
index d5922a8..4c53145 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1180,6 +1180,7 @@ struct urb {
atomic_t use_count; /* concurrent submissions counter */
atomic_t reject; /* submissions will fail */
int unlinked; /* unlink error code */
+ void *bounce_buffer; /* DMA bounce buffer for alignment */
/* public: documented fields in the urb that can be used by drivers */
struct list_head urb_list; /* list head for use by the urb's
diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index 2e3a4ea..a27df53 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -178,6 +178,8 @@ struct hc_driver {
const char *description; /* "ehci-hcd" etc */
const char *product_desc; /* product/vendor string */
size_t hcd_priv_size; /* size of private data */
+ unsigned dma_align_shift; /* Aligment requirement for DMA:
+ 0=byte 1=2 byte, 2=4 byte... */
/* irq handler */
irqreturn_t (*irq) (struct usb_hcd *hcd);
--
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