This is a note to let you know that I've just added the patch titled
usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth
to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-gadget-f_uac2-finalize-wmaxpacketsize-according-to-bandwidth.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 913e4a90b6f9687ac0f543e7b632753e4f51c441 Mon Sep 17 00:00:00 2001
From: Peter Chen <peter.chen@xxxxxxxxxxxxx>
Date: Thu, 30 Jul 2015 13:13:03 +0800
Subject: usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth
From: Peter Chen <peter.chen@xxxxxxxxxxxxx>
commit 913e4a90b6f9687ac0f543e7b632753e4f51c441 upstream.
According to USB Audio Device 2.0 Spec, Ch4.10.1.1:
wMaxPacketSize is defined as follows:
Maximum packet size this endpoint is capable of sending or receiving
when this configuration is selected.
This is determined by the audio bandwidth constraints of the endpoint.
In current code, the wMaxPacketSize is defined as the maximum packet size
for ISO endpoint, and it will let the host reserve much more space than
it really needs, so that we can't let more endpoints work together at
one frame.
We find this issue when we try to let 4 f_uac2 gadgets work together [1]
at FS connection.
[1]http://www.spinics.net/lists/linux-usb/msg123478.html
Acked-by: Daniel Mack <zonque@xxxxxxxxx>
Cc: andrzej.p@xxxxxxxxxxx
Cc: Daniel Mack <zonque@xxxxxxxxx>
Cc: tiwai@xxxxxxx
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <balbi@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/gadget/function/f_uac2.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -975,6 +975,29 @@ free_ep(struct uac2_rtd_params *prm, str
"%s:%d Error!\n", __func__, __LINE__);
}
+static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
+ struct usb_endpoint_descriptor *ep_desc,
+ unsigned int factor, bool is_playback)
+{
+ int chmask, srate, ssize;
+ u16 max_packet_size;
+
+ if (is_playback) {
+ chmask = uac2_opts->p_chmask;
+ srate = uac2_opts->p_srate;
+ ssize = uac2_opts->p_ssize;
+ } else {
+ chmask = uac2_opts->c_chmask;
+ srate = uac2_opts->c_srate;
+ ssize = uac2_opts->c_ssize;
+ }
+
+ max_packet_size = num_channels(chmask) * ssize *
+ DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1)));
+ ep_desc->wMaxPacketSize = cpu_to_le16(min(max_packet_size,
+ le16_to_cpu(ep_desc->wMaxPacketSize)));
+}
+
static int
afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
{
@@ -1070,10 +1093,14 @@ afunc_bind(struct usb_configuration *cfg
uac2->p_prm.uac2 = uac2;
uac2->c_prm.uac2 = uac2;
+ /* Calculate wMaxPacketSize according to audio bandwidth */
+ set_ep_max_packet_size(uac2_opts, &fs_epin_desc, 1000, true);
+ set_ep_max_packet_size(uac2_opts, &fs_epout_desc, 1000, false);
+ set_ep_max_packet_size(uac2_opts, &hs_epin_desc, 8000, true);
+ set_ep_max_packet_size(uac2_opts, &hs_epout_desc, 8000, false);
+
hs_epout_desc.bEndpointAddress = fs_epout_desc.bEndpointAddress;
- hs_epout_desc.wMaxPacketSize = fs_epout_desc.wMaxPacketSize;
hs_epin_desc.bEndpointAddress = fs_epin_desc.bEndpointAddress;
- hs_epin_desc.wMaxPacketSize = fs_epin_desc.wMaxPacketSize;
ret = usb_assign_descriptors(fn, fs_audio_desc, hs_audio_desc, NULL);
if (ret)
Patches currently in stable-queue which might be from peter.chen@xxxxxxxxxxxxx are
queue-4.2/usb-host-ehci-sys-delete-useless-bus_to_hcd-conversion.patch
queue-4.2/doc-usb-gadget-testing-using-the-updated-testusb.c.patch
queue-4.2/usb-gadget-f_uac2-finalize-wmaxpacketsize-according-to-bandwidth.patch
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