From mboxrd@z Thu Jan 1 00:00:00 1970 From: Knut Wohlrab Subject: Re: Devicetree: Initialization order of mmc block devices? Date: Wed, 18 Jul 2012 16:11:25 +0200 Message-ID: <5006C40D.300@de.bosch.com> References: <5006571A.7060103@de.bosch.com> <50068696.8070408@de.bosch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp2-v.fe.bosch.de ([139.15.237.6]:51257 "EHLO smtp2-v.fe.bosch.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751867Ab2GROOe (ORCPT ); Wed, 18 Jul 2012 10:14:34 -0400 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Jassi Brar Cc: "linux-arm-kernel@lists.infradead.org" , "linux-mmc@vger.kernel.org" , "Behme Dirk (CM-AI/PJ-CF32)" On 07/18/2012 03:47 PM, Jassi Brar wrote: > On 18 July 2012 15:19, Knut Wohlrab wrote: > >> If a SD card is inserted at boot time, its "mmcblk0", the embedded >> MMC (eMMC) device "mmcblk1". This makes it difficult to give the kernel the >> correct device for the eMMC root file system ("root=/dev/mmcblk?p1 ..."). >> > How about root=UUID= ? Because we are talking about an embedded device, it is very difficult to get a UUID of a eMMC partition into kernel command line with U-Boot. Handling of UUID is also a big effort at board manufacturing. Startup speed is very important for us. Searching for UUID on several MMC/SD devices will significant slow down the boot process. This problem can occur on many devices with embedded MMC and removable SD, e.g. smart phones. So I think we should find an solution to define MMC scan order or device number/name in a device tree. Thanks and regards Knut