From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from 4.mo2.mail-out.ovh.net ([87.98.172.75] helo=mo2.mail-out.ovh.net) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1T6vPj-0002j7-Nh for barebox@lists.infradead.org; Thu, 30 Aug 2012 03:27:29 +0000 Received: from mail21.ha.ovh.net (b6.ovh.net [213.186.33.56]) by mo2.mail-out.ovh.net (Postfix) with SMTP id 6C0A3DC5F1F for ; Thu, 30 Aug 2012 05:32:32 +0200 (CEST) Date: Thu, 30 Aug 2012 05:27:36 +0200 From: Jean-Christophe PLAGNIOL-VILLARD Message-ID: <20120830032736.GG18708@game.jcrosoft.org> References: <201208292317.03322.jbe@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <201208292317.03322.jbe@pengutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: barebox-bounces@lists.infradead.org Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: SD card experts wanted To: Juergen Beisert Cc: barebox@lists.infradead.org On 23:17 Wed 29 Aug , Juergen Beisert wrote: > Hi there, > > any SD/MMC card experts here? I have trouble with the current SD/MMC detection > code in Barebox. > The function sd_change_freq() in the file 'drivers/mci/mci-core.c' tries to > detect the max. transfer frequency the attached card can handle. Nothing > special here, but the following line in this routine fails on my system: > > if ((__be32_to_cpu(switch_status[4]) & 0x0f000000) == 0x01000000) > > It checks the clock speed capabilities returned from the card. As far as I > understand the "simplified SD card spec" the "0x01000000" means SDR25 speed, > which means still "single transfer per clock at 25 MHz clock rate". But the > sd_change_freq() routine sets the MMC_MODE_HS bit for this case in the card's > capabilities variable. The remaining routines in 'drivers/mci/mci-core.c' > then use 50 MHz for the transfer speed. > > This behaviour became an issue here, as my SDHC supports 50 MHz, but the > attached card only up to 25 MHz. After switching to 50 MHz, the card wasn't > able to respond anymore. > For SDHCs which supports only up to 25 MHz this misinterpretation is no issue, > as the routines still use the 25 MHz, and the SD card can still respond. > > "simplified SD card spec" talks about the bit's meaning: seems the regular > speed was SDR12 which means 12.5 MHz. Then SDR25 cards appear, which are also > called "high speed card". Could the MMC_MODE_HS just mean this "high speed" > and using it at 50 MHz is just some kind of typo? Or do MMCs act differently > and the code mixes SD and MMC features? I saw it too this isssue the mmc and sd feature are different with different spec so we need different code to interpret it see in the kernel Best Regards, J. _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox