On 07/22/2015 08:45 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: andrzej.p@xxxxxxxxxxx > Cc: 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 v2: > - Using DIV_ROUND_UP to calculate max packet size > > drivers/usb/gadget/function/f_uac2.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c > index 6d3eb8b..6eaa4c4 100644 > --- a/drivers/usb/gadget/function/f_uac2.c > +++ b/drivers/usb/gadget/function/f_uac2.c > @@ -987,6 +987,7 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn) > struct f_uac2_opts *uac2_opts; > struct usb_string *us; > int ret; > + u16 c_max_packet_size, p_max_packet_size; > > uac2_opts = container_of(fn->fi, struct f_uac2_opts, func_inst); > > @@ -1070,6 +1071,19 @@ 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 */ > + c_max_packet_size = uac2_opts->c_chmask * uac2_opts->c_ssize > + * DIV_ROUND_UP(uac2_opts->c_srate, 1000); > + p_max_packet_size = uac2_opts->p_chmask * uac2_opts->p_ssize > + * DIV_ROUND_UP(uac2_opts->p_srate, 1000); > + if ((c_max_packet_size > fs_epout_desc.wMaxPacketSize) || > + (p_max_packet_size > fs_epin_desc.wMaxPacketSize)) { > + dev_err(dev, "parameters are incorrect\n"); > + goto err; > + } > + fs_epin_desc.wMaxPacketSize = cpu_to_le16(c_max_packet_size); > + fs_epout_desc.wMaxPacketSize = cpu_to_le16(p_max_packet_size); > + > hs_epout_desc.bEndpointAddress = fs_epout_desc.bEndpointAddress; > hs_epout_desc.wMaxPacketSize = fs_epout_desc.wMaxPacketSize; Your calculation still doesn't take into account the endpoint's 'bInterval', and for HS, the value is still wrong. Daniel -- 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
