Re: [PATCH 1/2] usb: musb: use DMA mode 1 whenever possible

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Hello.

On 08/07/2012 05:09 PM, Roger Quadros wrote:

> Do not rely on any hints from gadget drivers and use DMA mode 1
> whenever we expect data of at least the endpoint's packet size and
> have not yet received a short packet.

> The last packet if short is always transferred using DMA mode 0.

> This patch fixes USB throughput issues in mass storage mode for
> host to device transfers.

> Signed-off-by: Roger Quadros <rogerq@xxxxxx>
> ---
>  drivers/usb/musb/musb_gadget.c |   30 ++++--------------------------
>  1 files changed, 4 insertions(+), 26 deletions(-)

> diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> index 8d2cce1..5c4392b 100644
> --- a/drivers/usb/musb/musb_gadget.c
> +++ b/drivers/usb/musb/musb_gadget.c
> @@ -707,12 +707,11 @@ static void rxstate(struct musb *musb, struct musb_request *req)
>  		fifo_count = musb_readw(epio, MUSB_RXCOUNT);
>  
>  		/*
> -		 * Enable Mode 1 on RX transfers only when short_not_ok flag
> -		 * is set. Currently short_not_ok flag is set only from
> -		 * file_storage and f_mass_storage drivers
> +		 *  use mode 1 only if we expect data of at least ep packet_sz
> +		 *  and have not yet received a short packet

   Why offset the comment text with 2 spaces?

>  		 */
> -
> -		if (request->short_not_ok && fifo_count == musb_ep->packet_sz)
> +		if ((request->length - request->actual >= musb_ep->packet_sz) &&
> +			(fifo_count >= musb_ep->packet_sz))

   'fifo_count' shouldn't ever be > packet size (unless there's babble error??).

WBR, Sergei

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