* Re: [Bugme-new] [Bug 15876] New: MMC initialisation: valid devices fail to init due to frequency check
[not found] <bug-15876-10286@https.bugzilla.kernel.org/>
@ 2010-05-21 21:48 ` Andrew Morton
0 siblings, 0 replies; only message in thread
From: Andrew Morton @ 2010-05-21 21:48 UTC (permalink / raw)
To: linux-mmc; +Cc: bugzilla-daemon, bugme-daemon, nick
(switched to email. Please respond via emailed reply-to-all, not via the
bugzilla web interface).
On Thu, 29 Apr 2010 10:26:39 GMT
bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=15876
>
> Summary: MMC initialisation: valid devices fail to init due to
> frequency check
> Product: Drivers
> Version: 2.5
> Kernel Version: 2.6.31
> Platform: All
> OS/Version: Linux
> Tree: Mainline
> Status: NEW
> Severity: normal
> Priority: P1
> Component: Flash/Memory Technology Devices
> AssignedTo: dwmw2@infradead.org
> ReportedBy: nick@leverton.org
> Regression: Yes
>
>
> I have a commercially available development board with MMC card socket (Atmel
> ATSTK1006 with AP7000). Prior to 2.6.31 this board could successfully
> initialise and use MMC cards. Since the minimum frequency enforcement to 400
> KHz was added in commit 8dfd0374be84793360db7fff2e635d2cd3bbcb21, this board
> can no longer detect MMC cards.
>
> Thanks to the following diagnostic patch: http://lkml.org/lkml/2010/1/4/291 I
> narrowed down the frequency range supported by this board. The host->f_min
> here is 136719 Hz.
>
> atmel_mci atmel_mci.0: Atmel MCI controller at 0xfff02400 irq 28, 1 slots
> mmc_rescan: trying 400000 Hz
> Waiting for root device /dev/mmcblk0p1...
> mmc_rescan: trying 300000 Hz
> mmc_rescan: trying 200000 Hz
> mmc_rescan: trying 136719 Hz
> mmc0: host does not support reading read-only switch. assuming
> write-enable.
> mmc0: new SD card at address 8fe4
> mmcblk0: mmc0:8fe4 SD02G 1.84 GiB
>
> I understand that the MMC spec allows frequency ranges between about 400 KHZ
> and 138 KHz. It seems that enforcing the minimum frequency to be the highest
> from the specification is causing the problem and causes an otherwise
> within-spec device such as this to fail to initialise.
>
> Other AVR32/AP7000 boards such as NGW100 seem OK with the same cards (Sandisk
> 2Gb) by the way and do work at full speed. It seems it may be due to this
> particular board layout that, although just about within spec, it is limited to
> the lower end of the range.
>
> Could I please ask the MMC people to re-visit this frequency check issue ? I'm
> opening this bug as a marker, thank you :)
>
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