Date: Mon, 6 Jul 2009 21:50:09 -0400 (EDT)
From: Alan Stern <stern@rowland.harvard.edu>
To: Zbigniew Luszpinski <zbiggy@o2.pl>
cc: linux-usb@vger.kernel.org, <linux-kernel@vger.kernel.org>
Subject: Re: PROBLEM: Nvidia OHCI chipset MCP78S (Geforce 8200) hangs on >
 1Mbit transfers if noapic/acpi=noirq is missing
In-Reply-To: <200907062340.56308.zbiggy@o2.pl>
Message-ID: <Pine.LNX.4.44L0.0907062147200.21717-100000@netrider.rowland.org>
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On Mon, 6 Jul 2009, Zbigniew Luszpinski wrote:

> I hope I find here someone who wrote or know Linux ohci driver so he/she knows 
> how to slow down ohci bulk/iso IO operations without breaking hotplug.

The speed of iso operations cannot be changed, because the transactions 
have to occur at a specified interval.

OHCI doesn't provide any way to slow down bulk operations either, once 
a bulk URB has been submitted.  The best you can do is slow down the 
rate of submission.  But you already tried that and it didn't work.

> It looks Linux ohci driver is more aggressive on ohci IO than windows one so 
> making Linux less timing demanding would help my MCP78S keep working.

I suspect you're looking in the wrong direction.  There's probably 
something wrong at a deeper level, in the chipset drivers for instance.

Alan Stern

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