> -----Original Message-----
> From: Gadiyar, Anand
> Sent: Wednesday, October 28, 2009 9:16 PM
> To: linux-usb@xxxxxxxxxxxxxxx
> Cc: Gadiyar, Anand; Felipe Balbi; David Brownell; Gupta, Ajay Kumar
> Subject: [PATCH] MUSB: Fix aborted RX-DMA path
>
> MUSB: Fix aborted RX-DMA path
>
> In the MUSB rxstate function, if channel_program() returns an
> error, then we use PIO mode to carry out that RX transfer.
>
> For this to work correctly, we need to de-assert DMAENAB in
> RXCSR.
>
> Signed-off-by: Anand Gadiyar <gadiyar@xxxxxx>
> Cc: Felipe Balbi <felipe.balbi@xxxxxxxxx>
> Cc: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx>
> Cc: Ajay Kumar Gupta <ajay.gupta@xxxxxx>
Ping?
Ajay, Felipe, David, Greg?
> ---
> (Resending with updated $SUBJECT. Sorry for the noise)
>
> In current code, this bug is purely academic, since channel_program()
> always returns success. However, if it ever failed, then the
> fix is needed. We spent some time to debug this when we deliberately
> made channel_program fail (to test the PIO path), so I think this
> fix is worth having.
>
> It's probably not required for the stable trees.
>
> diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> index 8b3c4e2..cfac24d 100644
> --- a/drivers/usb/musb/musb_gadget.c
> +++ b/drivers/usb/musb/musb_gadget.c
> @@ -688,8 +688,15 @@ static void rxstate(struct musb *musb, struct musb_request *req)
> transfer_size);
> }
>
> - if (use_dma)
> + if (use_dma) {
> return;
> + } else {
> + /* Need to clear DMAENAB for the
> + * backup PIO mode transfer to work
> + */
> + csr &= ~MUSB_RXCSR_DMAENAB;
> + musb_writew(epio, MUSB_RXCSR, csr);
> + }
> }
> #endif /* Mentor's DMA */
>
> --
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