On Fri, 20 Aug 2010, Maulik Mankad wrote:
> The USB stack maps the buffer for DMA if the controller supports DMA.
> MUSB controller can perform DMA as well as PIO transfers.
> The buffer needs to be unmapped before CPU can perform
> PIO data transfers.
>
> Signed-off-by: Maulik Mankad <x0082077@xxxxxx>
> Cc: Felipe Balbi <felipe.balbi@xxxxxxxxx>
> ---
> Based on 2.6.36-rc1
> Index: mainline/drivers/usb/musb/musb_host.c
> ===================================================================
> --- mainline.orig/drivers/usb/musb/musb_host.c
> +++ mainline/drivers/usb/musb/musb_host.c
> @@ -41,6 +41,7 @@
> #include <linux/errno.h>
> #include <linux/init.h>
> #include <linux/list.h>
> +#include <linux/dma-mapping.h>
>
> #include "musb_core.h"
> #include "musb_host.h"
> @@ -1326,6 +1327,15 @@ void musb_host_tx(struct musb *musb, u8
> */
> if (length > qh->maxpacket)
> length = qh->maxpacket;
> + /* Unmap the buffer so that CPU can use it */
> + if (urb->transfer_flags & URB_DMA_MAP_PAGE) {
> + dma_unmap_page(musb->controller,
> + urb->transfer_dma,
> + urb->transfer_buffer_length,
> + DMA_FROM_DEVICE);
> +
> + urb->transfer_flags &= ~URB_DMA_MAP_PAGE;
> + }
I can't tell if it would be correct here, but have you considered just
calling unmap_urb_for_dma() instead? (You'd have to make that routine
non-static and EXPORT it first.)
Alan Stern
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