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Date:      Thu, 2 May 2019 13:03:41 +0200
From:      Hans Petter Selasky <hps@selasky.org>
To:        "O'Connor, Daniel" <darius@dons.net.au>
Cc:        freebsd-usb@freebsd.org
Subject:   Re: USB transfers in device drivers
Message-ID:  <0d155a73-31b1-d901-9874-6cb017e6b5d5@selasky.org>
In-Reply-To: <64924732-9848-4AF6-B37E-4ED3889DB711@dons.net.au>
References:  <3B922C60-32E5-484E-8AFA-28FF7255CF2C@dons.net.au> <af8dfb40-1d48-d03b-465f-32b4361e91c0@selasky.org> <D73B37BF-8C28-4EE4-8026-5E9BF8B5C4AD@dons.net.au> <e4fdb075-faa8-7832-227b-89700e832162@selasky.org> <BBA09A08-52F1-413F-861A-D607F91531C1@dons.net.au> <bda9e5c6-e5c0-10c2-c46b-801be66cac5f@selasky.org> <64924732-9848-4AF6-B37E-4ED3889DB711@dons.net.au>

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On 2019-05-02 12:44, O'Connor, Daniel wrote:
> 
> 
>> On 2 May 2019, at 20:02, Hans Petter Selasky <hps@selasky.org> wrote:
>>
>> On 2019-05-02 11:18, O'Connor, Daniel wrote:
>>> OK, thanks.
>>> To be honest I would much prefer to work out why this particular hardware & software seem to drop the ball for such a long time - 50msec without the kernel getting to schedule something (on a basically idle system) is quite perplexing to me.
>>
>> Sounds like a lost IRQ issue. Did you try any of the EHCI quirks in hw.usb.ehci ?
> 
> No not, yet - thanks for the pointer!

The 50ms delay may also be due to a physical link data error and needed 
recovery through clear stall which is expensive.

--HPS



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