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: <stable@xxxxxxxxxxxxxxx> #v3.18+ Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx> --- Changes for v6: - Fix below sparse warning drivers/usb/gadget/function/f_uac2.c:997:35: sparse: restricted __le16 degrades to integer - Add Acked-by: Daniel Mack <zonque@xxxxxxxxx> 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..96d935b 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 = 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, 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) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
