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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