Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758306Ab1FVRga (ORCPT ); Wed, 22 Jun 2011 13:36:30 -0400 Received: from qmta12.emeryville.ca.mail.comcast.net ([76.96.27.227]:59057 "EHLO qmta12.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757878Ab1FVRg3 (ORCPT ); Wed, 22 Jun 2011 13:36:29 -0400 Date: Wed, 22 Jun 2011 10:35:44 -0700 From: matt mooney To: Kirill Smelkov , linux-usb@vger.kernel.org, Greg Kroah-Hartman , linux-uvc-devel@lists.berlios.de, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Alan Stern Subject: Re: [RFC, PATCH] USB: EHCI: Allow users to override 80% max periodic bandwidth Message-ID: <20110622173544.GD56479@haskell.muteddisk.com> Mail-Followup-To: Kirill Smelkov , linux-usb@vger.kernel.org, Greg Kroah-Hartman , linux-uvc-devel@lists.berlios.de, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Alan Stern References: <1308758567-8205-1-git-send-email-kirr@mns.spb.ru> <20110622173045.GC56479@haskell.muteddisk.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110622173045.GC56479@haskell.muteddisk.com> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6509 Lines: 169 On 10:30 Wed 22 Jun , matt mooney wrote: > On 20:02 Wed 22 Jun , Kirill Smelkov wrote: > > There are cases, when 80% max isochronous bandwidth is too limiting. > > > > For example I have two USB video capture cards which stream uncompressed > > video, and to stream full NTSC + PAL videos we'd need > > > > NTSC 640x480 YUV422 @30fps ~17.6 MB/s > > PAL 720x576 YUV422 @25fps ~19.7 MB/s > > > > isoc bandwidth. > > > > Now, due to limited alt settings in capture devices NTSC one ends up > > streaming with max_pkt_size=2688 and PAL with max_pkt_size=2892, both > > with interval=1. In terms of microframe time allocation this gives > > > > NTSC ~53us > > PAL ~57us > > > > and together > > > > ~110us > 100us == 80% of 125us uframe time. > > > > So those two devices can't work together simultaneously because the'd > > over allocate isochronous bandwidth. > > > > 80% seemed a bit arbitrary to me, and I've tried to raise it to 90% and > > both devices started to work together, so I though sometimes it would be > > a good idea for users to override hardcoded default of max 80% isoc > > bandwidth. > > There is nothing arbitrary about 80%. The USB 2.0 Specification constrains > periodic transfers for high-speed endpoints to 80% of the microframe. See > section 5.6.4. > Looking at the patch, I see that you probably already knew that. So I digress and defer to the USB experts ;) -mfm > > After all, isn't it a user who should decide how to load the bus? If I > > can live with 10% or even 5% bulk bandwidth that should be ok. I'm a USB > > newcomer, but that 80% seems to be chosen pretty arbitrary to me, just > > to serve as a reasonable default. > > > > NOTE: for two streams with max_pkt_size=3072 (worst case) both time > > allocation would be 60us+60us=120us which is 96% periodic bandwidth > > leaving 4% for bulk and control. I think this should work too. > > > > Signed-off-by: Kirill Smelkov > > Cc: Alan Stern > > --- > > drivers/usb/host/ehci-hcd.c | 16 ++++++++++++++++ > > drivers/usb/host/ehci-sched.c | 17 +++++++---------- > > 2 files changed, 23 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c > > index c606b02..1d36e72 100644 > > --- a/drivers/usb/host/ehci-hcd.c > > +++ b/drivers/usb/host/ehci-hcd.c > > @@ -112,6 +112,14 @@ static unsigned int hird; > > module_param(hird, int, S_IRUGO); > > MODULE_PARM_DESC(hird, "host initiated resume duration, +1 for each 75us\n"); > > > > +/* > > + * max periodic time per microframe > > + * (be careful, USB 2.0 requires it to be 100us = 80% of 125us) > > + */ > > +static unsigned int uframe_periodic_max = 100; > > +module_param(uframe_periodic_max, uint, S_IRUGO); > > +MODULE_PARM_DESC(uframe_periodic_max, "maximum allowed periodic part of a microframe, us"); > > + > > #define INTR_MASK (STS_IAA | STS_FATAL | STS_PCD | STS_ERR | STS_INT) > > > > /*-------------------------------------------------------------------------*/ > > @@ -571,6 +579,14 @@ static int ehci_init(struct usb_hcd *hcd) > > hcc_params = ehci_readl(ehci, &ehci->caps->hcc_params); > > > > /* > > + * tell user, if using non-standard (80% == 100 usec/uframe) bandwidth > > + */ > > + if (uframe_periodic_max != 100) > > + ehci_info(ehci, "using non-standard max periodic bandwith " > > + "(%u%% == %u usec/uframe)", > > + 100*uframe_periodic_max/125, uframe_periodic_max); > > + > > + /* > > * hw default: 1K periodic list heads, one per frame. > > * periodic_size can shrink by USBCMD update if hcc_params allows. > > */ > > diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c > > index d12426f..fb374f2 100644 > > --- a/drivers/usb/host/ehci-sched.c > > +++ b/drivers/usb/host/ehci-sched.c > > @@ -172,7 +172,7 @@ periodic_usecs (struct ehci_hcd *ehci, unsigned frame, unsigned uframe) > > } > > } > > #ifdef DEBUG > > - if (usecs > 100) > > + if (usecs > uframe_periodic_max) > > ehci_err (ehci, "uframe %d sched overrun: %d usecs\n", > > frame * 8 + uframe, usecs); > > #endif > > @@ -709,11 +709,8 @@ static int check_period ( > > if (uframe >= 8) > > return 0; > > > > - /* > > - * 80% periodic == 100 usec/uframe available > > - * convert "usecs we need" to "max already claimed" > > - */ > > - usecs = 100 - usecs; > > + /* convert "usecs we need" to "max already claimed" */ > > + usecs = uframe_periodic_max - usecs; > > > > /* we "know" 2 and 4 uframe intervals were rejected; so > > * for period 0, check _every_ microframe in the schedule. > > @@ -1286,9 +1283,9 @@ itd_slot_ok ( > > { > > uframe %= period; > > do { > > - /* can't commit more than 80% periodic == 100 usec */ > > + /* can't commit more than uframe_periodic_max usec */ > > if (periodic_usecs (ehci, uframe >> 3, uframe & 0x7) > > - > (100 - usecs)) > > + > (uframe_periodic_max - usecs)) > > return 0; > > > > /* we know urb->interval is 2^N uframes */ > > @@ -1345,7 +1342,7 @@ sitd_slot_ok ( > > #endif > > > > /* check starts (OUT uses more than one) */ > > - max_used = 100 - stream->usecs; > > + max_used = uframe_periodic_max - stream->usecs; > > for (tmp = stream->raw_mask & 0xff; tmp; tmp >>= 1, uf++) { > > if (periodic_usecs (ehci, frame, uf) > max_used) > > return 0; > > @@ -1354,7 +1351,7 @@ sitd_slot_ok ( > > /* for IN, check CSPLIT */ > > if (stream->c_usecs) { > > uf = uframe & 7; > > - max_used = 100 - stream->c_usecs; > > + max_used = uframe_periodic_max - stream->c_usecs; > > do { > > tmp = 1 << uf; > > tmp <<= 8; > > -- > > 1.7.6.rc1 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/