From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v3] mmc: mxs-mmc: add mmc host driver for i.MX23/28 Date: Tue, 22 Feb 2011 17:15:07 +0100 Message-ID: <201102221715.07480.arnd@arndb.de> References: <1298284528-14761-1-git-send-email-shawn.guo@freescale.com> <20110222085256.GA19871@S2100-06.ap.freescale.net> <20110222103349.GA2755@pengutronix.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.126.171]:62717 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754548Ab1BVQPh (ORCPT ); Tue, 22 Feb 2011 11:15:37 -0500 In-Reply-To: <20110222103349.GA2755@pengutronix.de> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Wolfram Sang Cc: Shawn Guo , linux-mmc@vger.kernel.org, cjb@laptop.org, linux@arm.linux.org.uk, linux-arm-kernel@lists.infradead.org On Tuesday 22 February 2011, Wolfram Sang wrote: > # mount -t vfat /dev/mmcblk0p1 /mnt > # dd if=/mnt/test.dat of=/tmp/a bs=1024 > # umount /mnt > # ./dd --version > dd (coreutils) 8.5 In general, you should try to rule out file system, garbage collection, partitioning and cache effects. With coreutils dd, a good command is dd if=/dev/zero of=/dev/mmcblk0 bs=64K count=64 seek=256 oflag=direct * Always write multiples of 4 MB to avoid garbage collection * smaller block sizes may be faster, so writing 64 times 64K may be better than writing 4 MB once, depending on the card * don't write to the FAT area, so start writing at 16 MB into the device. * use direct I/O to bypass the page cache. * read from /dev/zero instead of a disk file to avoid measuring the wrong thing Arnd