Commit 0560c9c5 authored Sep 24, 2021 by Pavel Hofman Committed by Greg Kroah-Hartman Oct 05, 2021

usb: gadget: f_uac2: fixed EP-IN wMaxPacketSize



Async feedback patches broke enumeration on Windows 10 previously fixed
by commit 789ea773 ("usb: gadget: f_uac2: always increase endpoint
max_packet_size by one audio slot").

While the existing calculation for EP OUT capture for async mode yields
size+1 frame due to uac2_opts->fb_max > 0, playback side lost the +1
feature.  Therefore the +1 frame addition must be re-introduced for
playback. Win10 enumerates the device only when both EP IN and EP OUT
max packet sizes are (at least) +1 frame.

Fixes: e89bb428 ("usb: gadget: u_audio: add real feedback implementation")
Cc: stable <stable@vger.kernel.org>
Tested-by: Henrik Enquist <henrik.enquist@gmail.com>
Tested-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Pavel Hofman <pavel.hofman@ivitera.com>
Link: https://lore.kernel.org/r/20210924080027.5362-1-pavel.hofman@ivitera.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 04d2b755

drivers/usb/gadget/function/f_uac2.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -674,11 +674,17 @@ static int set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
		ssize = uac2_opts->c_ssize;
		}

		if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC))
		if (!is_playback && (uac2_opts->c_sync == USB_ENDPOINT_SYNC_ASYNC)) {
		// Win10 requires max packet size + 1 frame
		srate = srate * (1000 + uac2_opts->fb_max) / 1000;

		// updated srate is always bigger, therefore DIV_ROUND_UP always yields +1
		max_size_bw = num_channels(chmask) * ssize *
		(DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1))));
		} else {
		// adding 1 frame provision for Win10
		max_size_bw = num_channels(chmask) * ssize *
		DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
		(DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1))) + 1);
		}
		ep_desc->wMaxPacketSize = cpu_to_le16(min_t(u16, max_size_bw,
		max_size_ep));