> On 07/28/2015 11:17 AM, Peter Chen wrote:
> > 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
> >
> > Cc: andrze...@samsung.com
> > Cc: Daniel Mack <zon...@gmail.com>
> > Cc: ti...@suse.de
> > Cc: <sta...@vger.kernel.org> #v3.18+
> > Cc: Alan Stern <st...@rowland.harvard.edu>
> > Signed-off-by: Peter Chen <peter.c...@freescale.com>
>
> Looks good to me now! I currently don't have hardware to test this on, though.
>
I have tested it.
Peter
> Acked-by: Daniel Mack <zon...@gmail.com>
>
>
> Thanks,
> Daniel
>
> > ---
> >
> > Changes for v5:
> > - Add additional parameters 'is_playback' for helper
> > - Add const for parameter 'struct f_uac2_opts *uac2_opts'
> > - Put all three int variables at one line
> > - Fix the CodeStyle problem
> >
> > Changes for v4:
> > - Add helper set_ep_max_packet_size to calculate max packet size
> >
> > Changes for v3:
> > - Consider 'bInterval' to calculate wMaxPacketSize
> > - playback endpoint is IN ep, and capture endpoint is OUT ep
> >
> > Changes for v2:
> > - Using DIV_ROUND_UP to calculate max packet size
> >
> > drivers/usb/gadget/function/f_uac2.c | 31
> > +++++++++++++++++++++++++++++--
> > 1 file changed, 29 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/function/f_uac2.c
> > b/drivers/usb/gadget/function/f_uac2.c
> > index 5318615..fa93d79 100644
> > --- 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, struct
> usb_ep *ep)
> > "%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 = min(cpu_to_le16(max_packet_size),
> > + 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, struct
> usb_function *fn)
> > 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)
> >
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