(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@xxxxxxxxxxxxxxxxxxx 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@xxxxxxxxxxxxx > ReportedBy: nick@xxxxxxxxxxxx > 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 :) > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
