On Fri, 11 Jan 2008 18:22:14 +0800
"Bryan Wu" <[EMAIL PROTECTED]> wrote:
>
> I guess it is for MMC/SD card insert detection. Is it related with the
> 4-bit MMC and 4-bit SD?
> Actually, there are some issues about the card insert detection on
> BF54x SDH. Following is some comments of our bfin-sdh driver which is
> in the development.
>
Right. As you've noticed, that pin is not a reliable way of detecting cards. It
works badly, if all, for MMC cards. And some SD cards also lack the necessary
pull-up.
But for the matter at hand, some cards might rely on the pull-up being there,
so you'll get bit-errors without it. I don't have time to double check the
specs right now, but it might explain why you're seeing problems with MMC and
not SD.
Btw, the MMC core sends you ios information on how you should fiddle with that
bit. It was needed on a Winbond controller (the wbsd driver) as some models
relied on it for card detection.
Rgds
--
-- Pierre Ossman
Linux kernel, MMC maintainer http://www.kernel.org
PulseAudio, core developer http://pulseaudio.org
rdesktop, core developer http://www.rdesktop.org
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