From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from svenfoo.org ([82.94.215.22]:33784 "EHLO mail.zonque.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751015AbbG0INM (ORCPT ); Mon, 27 Jul 2015 04:13:12 -0400 Subject: Re: [PATCH v3 1/2] usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth To: Peter Chen , balbi@ti.com References: <1437979907-29976-1-git-send-email-peter.chen@freescale.com> Cc: linux-usb@vger.kernel.org, andrzej.p@samsung.com, Daniel Mack , tiwai@suse.de, stable@vger.kernel.org, Alan Stern From: Daniel Mack Message-ID: <55B5E813.2080805@zonque.org> Date: Mon, 27 Jul 2015 10:13:07 +0200 MIME-Version: 1.0 In-Reply-To: <1437979907-29976-1-git-send-email-peter.chen@freescale.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: On 07/27/2015 08:51 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@samsung.com > Cc: Daniel Mack > Cc: tiwai@suse.de > Cc: #v3.18+ > Cc: Alan Stern > Signed-off-by: Peter Chen > --- > > 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 | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c > index 6d3eb8b..51ca32d 100644 > --- a/drivers/usb/gadget/function/f_uac2.c > +++ b/drivers/usb/gadget/function/f_uac2.c > @@ -987,6 +987,8 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn) > struct f_uac2_opts *uac2_opts; > struct usb_string *us; > int ret; > + u16 max_packet_size; > + struct usb_endpoint_descriptor *ep_desc; > > uac2_opts = container_of(fn->fi, struct f_uac2_opts, func_inst); > > @@ -1070,10 +1072,37 @@ 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 */ > + ep_desc = &fs_epin_desc; > + max_packet_size = num_channels(uac2_opts->p_chmask) * > + uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate, > + 1000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); > + > + ep_desc = &fs_epout_desc; > + max_packet_size = num_channels(uac2_opts->c_chmask) * > + uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate, > + 1000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); > + > + ep_desc = &hs_epin_desc; > + max_packet_size = num_channels(uac2_opts->p_chmask) * > + uac2_opts->p_ssize * DIV_ROUND_UP(uac2_opts->p_srate, > + 8000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); > + > + ep_desc = &hs_epout_desc; > + max_packet_size = num_channels(uac2_opts->c_chmask) * > + uac2_opts->c_ssize * DIV_ROUND_UP(uac2_opts->c_srate, > + 8000 / (1 << (ep_desc->bInterval - 1))); > + ep_desc->wMaxPacketSize = min(cpu_to_le16(max_packet_size), > + ep_desc->wMaxPacketSize); Basically, the same operation is repeated 4 times here. What about factoring the code out to a helper function, so that the call site looks like this: set_ep_max_packet_size(&fs_epin_desc, uac2_opts, 1000); set_ep_max_packet_size(&fs_epout_desc, uac2_opts, 1000); set_ep_max_packet_size(&hs_epin_desc, uac2_opts, 8000); set_ep_max_packet_size(&hs_epout_desc, uac2_opts, 8000); Other than that, the patch now looks good to me! Thanks, Daniel > + > 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) >