linux-kernel - [PATCH v4 0/2] USB: EHCI: Allow users to override 80% max periodic bandwidth

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Date:	Sun,  3 Jul 2011 20:36:55 +0400
From:	Kirill Smelkov <kirr@....spb.ru>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	matt mooney <mfm@...eddisk.com>,
	Greg Kroah-Hartman <gregkh@...e.de>, linux-usb@...r.kernel.org,
	linux-uvc-devel@...ts.berlios.de, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, Kirill Smelkov <kirr@....spb.ru>
Subject: [PATCH v4 0/2] USB: EHCI: Allow users to override 80% max periodic bandwidth

There are cases, when 80% max isochronous bandwidth is too limiting.

Let's allow knowledgeable users to override that 80% max limit explicitly for
extreme cases, like 2 high bandwidth isochronously streaming devices on the
same High Speed USB bus in order to make them work simultaneously.

See full details in PATCH 2/2.


Changes since v3:

 - as suggested by Greg KH added new entry to Documentation/ABI/;

 - for consistency also touched Documentation/usb/ehci.txt reminding we now
   have new setting for periodic transfers scheduler.

   The base text in-there requires much updating regarding isochronous
   transfers, so only "TBD" with brief description was put because I'm not the best
   person to get EHCI description into shape;

 - added ACK to PATCH 2/2 from Alan Stern based on previous feedback. (I hope
   it's still semi-ok to put it, inspite of adding new not-reviewed text into
   docs);

 - minor cosmetics in patch descriptions.


Changes since v2:

 - changed the copyright in ehci-sysfs from David Brownell to Alan Stern;

 - added ACK to PATCH 1/2 from Alan Stern;

 - inspired by concerns raised by Sarah Sharp, added more details about testing
   done on N10 chipset, system stability, and that no-harm-is-done for those,
   who do not change uframe_periodic_max from default 100us;

 - when decreasing uframe_periodic_max, compare with the maximum number of
   microseconds already allocated for any uframe, instead of stopping as soon
   as it finds something above the new limit.


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 bandwidth 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;

Kirill Smelkov (2):
  USB: EHCI: Move sysfs related bits into ehci-sysfs.c
  USB: EHCI: Allow users to override 80% max periodic bandwidth

 Documentation/ABI/testing/sysfs-module |   23 ++++
 Documentation/usb/ehci.txt             |    2 +
 drivers/usb/host/ehci-hcd.c            |   11 ++-
 drivers/usb/host/ehci-hub.c            |   75 -------------
 drivers/usb/host/ehci-sched.c          |   17 +--
 drivers/usb/host/ehci-sysfs.c          |  190 ++++++++++++++++++++++++++++++++
 drivers/usb/host/ehci.h                |    2 +
 7 files changed, 233 insertions(+), 87 deletions(-)
 create mode 100644 drivers/usb/host/ehci-sysfs.c

-- 
1.7.6.rc3

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