linux-kernel - RE: MMC: Card detection through pin CD/DAT3 issue

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <83116F0A4FF67A4F97BA0B6E408C48E301DAB4DF@zuerich.BC-Int.NET>
Date:	Tue, 18 Mar 2008 13:24:33 +0100
From:	"Wappler Marcel" <Marcel.Wappler@...dgeco.net>
To:	"Pierre Ossman" <drzeus-mmc@...eus.cx>
Cc:	<linux-kernel@...r.kernel.org>
Subject: RE: MMC: Card detection through pin CD/DAT3 issue

Hi Pierre,

>> With this detection scheme I have some dificulties togehter
>> with the internal working of the current MMC stack:
>> The controller cannot detect a newly inserted card if the card power 
>> is switched of. This is due to the fact that the SD card applies the 
>> internal card detection pull up after it powered up. If there is no 
>> power -> no powering up -> no pull up. (besides the fact that a pull 
>> up needs power to for doing its work :-) )
>> 

> Then you have broken hardware. The specs clearly state that the 
> controller must be able to detect cards without powering up the
> cards. Also, the cards must implement the pull-up in a way that
> behaves like a resistor. So there should be no requirement for 
> full power there either.

I have found this requirement in the SD host controller spec:
"The card detect is active regardless of the SD Bus Power."

I wonder how the card should be able to pull up the CD/DAT3 Pad to VCC
if its only VCC pad is not connected to VCC due to the fact that the host
controller has switched off the cards power - any idea how this could be
managed?

There is a SD card spec section somewhere which statet that:
"If one of the supply pins (VDD or VSS) is not connected properly, then
the current is drawn through a data line to supply the card."

Maybe this is the key in understanding ho the pull up without VCC connected
works?

Thanks,
marcel
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/