Am Mittwoch, 1. September 2010, 11:41:06 schrieb Ming Lei:
> > + if (urb->bounce_buffer) {
> > + if (dir == DMA_FROM_DEVICE)
> > + memcpy(urb->transfer_buffer,
> > + urb->bounce_buffer,
> > + urb->transfer_buffer_length);
> > + kfree(urb->bounce_buffer);
>
> dma_unmap_single is needed for bounce_buffer.
Good catch.
> > + }
> > + } 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;
>
> Suppose hcd->driver->dma_align_shift is zero and HC is byte aligned DMA
> enabled, this means DMA is doable between byte aligned memory and HC,
> but this does __not__ mean it is safe to do dma mapping or unmapping between
> CPU and byte aligned memory, which may cause sync issues between memory
> and CPU cache.
OK, so what tells us on which alignment a CPU can map?
Regards
Oliver
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
