linux-kernel - Re: [PCMCIA] Solved: No USB 2.0 (ehci) in PCMCIA slot on E7110

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Date:	Mon, 12 Aug 2013 23:25:07 +0200
From:	Andreas Mohr <andi@...as.de>
To:	Thomas Richter <richter@....uni-stuttgart.de>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org, Josep Lladonosa <jlladono@...il.com>,
	dahinds@...rs.sourceforge.net, linux-pcmcia@...ts.infradead.org,
	Tomáš Kováčik <nail@...omain.sk>
Subject: Re: [PCMCIA] Solved: No USB 2.0 (ehci) in PCMCIA slot on E7110

Hi,

that means we're talking this one (have you had a look at Bugzilla #15014?
Might be useful...):

commit 35169529093be3bbef70afd3c4125e35cece7e03
Author: Wolfram Sang <w.sang@...gutronix.de>
Date:   Sun Jan 10 09:41:24 2010 +0100

    pcmcia/yenta: add module parameter for O2 speedups
    
    O2-bridges can do read prefetch and write burst. However, for some combinations
    of older bridges and cards, this causes problems, so it is disabled for those
    bridges. Now, as some users know their setup works with the speedups enabled, a
    new parameter is introduced to the driver. Now, a user can specifically enable
    or disable these features, while the default is what we have today: detect the
    bridge and decide accordingly. Fixes Bugzilla entry 15014.
    
    Simplify and unify the printouts, fix a whitespace issue while we are here.
    
    Signed-off-by: Wolfram Sang <w.sang@...gutronix.de>
    Tested-by: frodone@...il.com
    [linux@...inikbrodowski.net: whitespace fixes]
    Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>


And my

git log -p drivers/pcmcia/o2micro.h

also mentions

commit 1ff84890b62b20823b3697a6041bbec1b5280cee
Author: Tomas Kovacik <nail@...omain.sk>
Date:   Sun Jul 26 22:04:58 2009 +0200

    pcmcia: disable prefetch/burst for OZ6933
    
    Problems have been reported [1], so disable prefetch/burst, to be on the safe
    side.
    
    [1] http://www.mail-archive.com/linux-pcmcia@lists.infradead.org/msg02048.html
    
    Signed-off-by: Tomáš Kováčik <nail@...omain.sk>
    Signed-off-by: Wolfram Sang <w.sang@...gutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>



A useful idea would be to kindly ask Tomáš Kováčik (CC'd) about details of his system
(4 years later - but hopefully...), specifically lspci -vv -xxx or some such
(especially the revision of that controller might be *different*,
so perhaps only *some* 6933 remained affected, whereas newer ones of that
possibly more modern chipset ID started to get corrected).
Or quite likely there's some sufficiently detailed lspci log of that hardware
out on the internet somewhere...


Note that there's the comment
"for some bridges it is at 0x94, for others at 0xD4. it's
         * ok to write to both registers on all O2 bridges."
, yet our 6933 support lines were added *later*,
so there's a faint possibility that the compatibility statement
actually does not apply to this chipset.



And of course there remains the question *why* such slow communication
would then cause such severe USB HC communication trouble.
There might be some safeguard missing there as well...


And kudos to the patch submitters for having supplied
such nicely detailed commit logs!
(although mentioning the title of URLs probably would have been even better)



> Note that this is only a 1.7Ghz Pentium-4-M dinosaur.

That means you really don't want to know which kinds of machines I am using ;)
(yes, I'm sitting at a CardBus box here, too)
((TI CardBus controller))


Greetings,

Andreas Mohr (KA/S)
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