On Wed, Apr 13, 2016 at 03:01:02PM +0300, Semen Protsenko wrote:
> From: Sam Protsenko <semen.protse...@linaro.org>
>
> Some UDC controllers may require buffer size to be aligned to
> wMaxPacketSize. It's indicated by gadget->quirk_ep_out_aligned_size
> field being set to "true" (in UDC driver code). In that case
> rx_bytes_expected must be aligned to wMaxPacket size, otherwise stuck on
> transaction will happen. For example, it's required by DWC3 controller
> data manual:
>
> section 8.2.3.3 Buffer Size Rules and Zero-Length Packets:
>
> For OUT endpoints, the following rules apply:
> - The BUFSIZ field must be ≥ 1 byte.
> - The total size of a Buffer Descriptor must be a multiple of
> MaxPacketSize
> - A received zero-length packet still requires a MaxPacketSize buffer.
> Therefore, if the expected amount of data to be received is a multiple
> of MaxPacketSize, software should add MaxPacketSize bytes to the buffer
> to sink a possible zero-length packet at the end of the transfer.
>
> But other UDC controllers don't need such alignment, so mentioned field
> is set to "false". If buffer size is aligned to wMaxPacketSize, those
> controllers may stuck on transaction. The example is DWC2.
>
> This patch checks gadget->quirk_ep_out_aligned_size field and aligns
> rx_bytes_expected to wMaxPacketSize only when it's needed.
[snip]
> @@ -435,12 +438,18 @@ static unsigned int rx_bytes_expected(unsigned int
> maxpacket)
> return 0;
> if (rx_remain > EP_BUFFER_SIZE)
> return EP_BUFFER_SIZE;
> +
> + if (!quirk_ep_out_aligned_size)
> + goto out;
> +
> if (rx_remain < maxpacket) {
> rx_remain = maxpacket;
> } else if (rx_remain % maxpacket != 0) {
> rem = rx_remain % maxpacket;
> rx_remain = rx_remain + (maxpacket - rem);
> }
> +
> +out:
> return rx_remain;
Can we do:
/* Only continue on conntrollers that require additional padding */
if (!quirk_ep_out_aligned_size)
return rx_remain;
Or similar comment, so it's clear in the code why we're doing this and
no need for a new goto here. Thanks!
--
Tom
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