[PATCH 5.14 004/151] usb: gadget: f_uac2: fixed EP-IN wMaxPacketSize

Greg Kroah-Hartman
2021-10-11T14:02:58Z

From: Pavel Hofman <pavel.hofman@ivitera.com>

commit 0560c9c552c1815e7b480bc11fd785fefc82bb27 upstream.

Async feedback patches broke enumeration on Windows 10 previously fixed
by commit 789ea77310f0 ("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: e89bb4288378 ("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>
---
drivers/usb/gadget/function/f_uac2.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -593,11 +593,17 @@ static int set_ep_max_packet_size(const
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;
-
- max_size_bw = num_channels(chmask) * ssize *
- DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
+ // 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))) + 1);
+ }
ep_desc->wMaxPacketSize = cpu_to_le16(min_t(u16, max_size_bw,
max_size_ep));