On Wed, Jul 22, 2015 at 10:04:30AM +0200, Daniel Mack wrote: > 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. > > You mean I need to consider high bandwidth ISO transfer (3 packets per SoF)? -- Best Regards, Peter Chen -- 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
