From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [Bugme-new] [Bug 15876] New: MMC initialisation: valid devices fail to init due to frequency check Date: Fri, 21 May 2010 14:48:51 -0700 Message-ID: <20100521144851.d8c4342e.akpm@linux-foundation.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:40313 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755483Ab0EUVtg (ORCPT ); Fri, 21 May 2010 17:49:36 -0400 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: linux-mmc@vger.kernel.org Cc: bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org, nick@leverton.org (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 :) >