On Thu, Jun 30, 2011 at 11:01:01AM -0700, Sarah Sharp wrote:
> On Fri, Jun 24, 2011 at 08:48:06PM +0400, Kirill Smelkov wrote:
> >
> > Changes since v1:
> >
> >
> > - dropped RFC status as "this seems like the sort of feature somebody might
> > reasonably want to use -- if they know exactly what they're doing";
> >
> > - new preparatory patch (1/2) which moves already-in-there sysfs code into
> > ehci-sysfs.c;
> >
> > - moved uframe_periodic_max parameter from module option to sysfs attribute,
> > so that it can be set per controller and at runtime, added validity checks;
> >
> > - clarified a bit bandwith analysis for 96% max periodic setup as noticed by
> > Alan Stern;
> >
> > - clarified patch description saying that set in stone 80% max periodic is
> > specified by USB 2.0;
>
> Have you tested this patch by maxing out this bandwidth on various
> types of host controllers? It's entirely possible that you'll run into
> vendor-specific bugs if you try to pack the schedule with isochronous
> transfers. I don't think any hardware designer would seriously test or
> validate their hardware with a schedule that is basically a violation of
> the USB bus spec (more than 80% for periodic transfers).
I've only tested it to work on my HP Mini 5103 with N10 chipset:
kirr@mini:~$ lspci
00:00.0 Host bridge: Intel Corporation N10 Family DMI Bridge
00:02.0 VGA compatible controller: Intel Corporation N10 Family Integrated Graphics Controller
00:02.1 Display controller: Intel Corporation N10 Family Integrated Graphics Controller
00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 02)
00:1c.0 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 1 (rev 02)
00:1c.3 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 4 (rev 02)
00:1d.0 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #3 (rev 02)
00:1d.3 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #4 (rev 02)
00:1d.7 USB Controller: Intel Corporation N10/ICH 7 Family USB2 EHCI Controller (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev e2)
00:1f.0 ISA bridge: Intel Corporation NM10 Family LPC Controller (rev 02)
00:1f.2 SATA controller: Intel Corporation N10/ICH7 Family SATA AHCI Controller (rev 02)
01:00.0 Network controller: Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01)
02:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8059 PCI-E Gigabit Ethernet Controller (rev 11)
The system works stable with 110us/uframe (~88%) isoc bandwith allocated for
integrated UVC webcam and external EM28XX based capture board.
> But if Alan is fine with giving users a way to shoot themselves in the
> foot, and it's disabled by default, then I don't particularly mind this
> patch.
Yes, it is disabled by default, I mean max periodic bandwidth is set to
100us/uframe by default exactly as it was before the patch. So only
those of us who need the extreme settings are taking the risk - normal
users who do not alter uframe_periodic_max attribute should not see any
change at all.
Thanks for commenting. I'll extend my testing information and notes on
do-not-do-harm bahaviour in updated patch.
Kirill
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