Date: Tue, 20 Jan 2009 11:40:51 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: mav@FreeBSD.org Cc: freebsd-arm@FreeBSD.org Subject: Re: Mount root from SD card? Message-ID: <20090120.114051.-854291995.imp@bsdimp.com> In-Reply-To: <49760E8E.1000609@FreeBSD.org> References: <1232400185.00063286.1232389201@10.7.7.3> <1232450582.00063538.1232438401@10.7.7.3> <49760E8E.1000609@FreeBSD.org>
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In message: <49760E8E.1000609@FreeBSD.org>
Alexander Motin <mav@FreeBSD.org> writes:
: Krassimir Slavchev wrote:
: > -----BEGIN PGP SIGNED MESSAGE-----
: > Hash: SHA1
: >
: > M. Warner Losh wrote:
: > ...
: >> mmcsd0: 1983MB <SD Memory Card> at mmc0 30MHz/1bit
: >> Trying to mount root from ufs:/dev/mmcsd0s1
: >>
: >> Manual root filesystem specification:
: >> <fstype>:<device> Mount <device> using filesystem <fstype>
: >> eg. ufs:/dev/da0a
: >> ? List valid disk boot devices
: >> <empty line> Abort manual input
: >>
: >> mountroot> ?
: >>
: >> List of GEOM managed disk devices:
: >> mmcsd0
: >>
: >>> Looks like that should be working.
: >>> mav@ has done a lot of hacking on the mmc code...
: >>> Do you have 1 wire or 4 wires for your mmc bus on your board?
: >
: > On the board all 4 bus wires are connected (MCD A0-A3) but I've never
: > seen working 4-bit mode on AT91RM9200 (See PR128987 too).
:
: I have just committed MMCBR_IVAR_CAPS implementation into CURRENT.
: Without having it implemented, results can be unpredictable. For
: example, mmc layer could enable high-speed timings to reach 30MHz, but
: this mode is not implemented for this controller. Booting with verbose
: messages enabled could give a bit more information.
This controller's driver should do the right thing when given a too
high bus speed: clamp it to the maximum...
However, maybe the clamps are right. The above symptom was what I'd
see when the data read in was corrupted. It is the whole reason I
never enabled the multi-block read for this controller. I could never
make it work well enough to even make mountroot happy.
: What's about 4-bit mode, I see some sc->wire4 variable checked by the
: driver, which is never initialized. I don't very understand how this
: thing expected to work.
It is initialized to zero. It is expected that there will be a
different mechanism in the future to set it generically on a per-board
basis.
: PS: For MMC cards bus width testing routine implemented. May be we could
: do something alike for SD cards. It is not part of SD specification, but
: may be we could just issue some other command, transferring data, to
: check effective bus width.
That would be cool.
Warner
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