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.
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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