From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from metis.extern.pengutronix.de (metis.extern.pengutronix.de [83.236.181.26]) by ozlabs.org (Postfix) with ESMTP id D31F8DDE11 for ; Wed, 7 May 2008 23:22:38 +1000 (EST) Date: Wed, 7 May 2008 15:25:14 +0200 From: Sascha Hauer To: David Woodhouse Subject: Re: jffs2 and unaligned access Message-ID: <20080507132514.GF4326@pengutronix.de> References: <20080507102724.GE4326@pengutronix.de> <1210157630.25560.884.camel@pmac.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1210157630.25560.884.camel@pmac.infradead.org> Cc: linuxppc-dev@ozlabs.org, linux-mtd@lists.infradead.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, May 07, 2008 at 11:53:49AM +0100, David Woodhouse wrote: > On Wed, 2008-05-07 at 12:27 +0200, Sascha Hauer wrote: > > memcpy_from/to_io() use word aligned accesses on the io side of memory. > > The MPC5200 local plus bus where our flashes are connected does not > > allow unaligned accesses, so we have to use the io versions of memcpy. > > But this region of flash is marked as suitable for execute-in-place, > otherwise the point() function wouldn't be working to give a direct > pointer to it. It sounds like we shouldn't be allowing that. It actually is suitable for execute-in-place. It's the flash U-Boot starts from. The compiler will generate a proper alignment for you. > > Which in turn means that perhaps we should have a property in the > corresponding node in the device-tree which indicates that it's not > suitable for direct access? So far we did not work with the device-tree flash binding but with the physmap-flash driver, but ok, this is subject to change anyway. I gave it a quick try to disable direct accesses. It works, but has a 1:10 performance impact on mounting a jffs2. At least it's a clean solution. Sascha -- Pengutronix e.K. - Linux Solutions for Science and Industry ----------------------------------------------------------- Kontakt-Informationen finden Sie im Header dieser Mail oder auf der Webseite -> http://www.pengutronix.de/impressum/ <-