From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4E11B9F7.5080606@atmel.com> Date: Mon, 04 Jul 2011 15:02:47 +0200 From: Nicolas Ferre MIME-Version: 1.0 To: Russell King - ARM Linux Subject: Re: [RFC PATCH] MTD: atmel_nand: optimize read/write buffer functions References: <1309261856-27402-1-git-send-email-nicolas.ferre@atmel.com> <20110628111043.GH6588@pengutronix.de> <20110628145937.GG21898@n2100.arm.linux.org.uk> <4E0B2427.9020202@atmel.com> <20110629133124.GO21898@n2100.arm.linux.org.uk> In-Reply-To: <20110629133124.GO21898@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: hong.xu@atmel.com, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, =?ISO-8859-1?Q?Uwe_Kleine-K=F6nig?= List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Le 29/06/2011 15:31, Russell King - ARM Linux : > On Wed, Jun 29, 2011 at 03:09:59PM +0200, Nicolas Ferre wrote: >> Le 28/06/2011 16:59, Russell King - ARM Linux : >>> I think you need to read Documentation/bus-virt-phys-mapping.txt, >>> particularly the part after "NOTE NOTE NOTE". >>> >>> Dereferencing ioremap'd memory is not permitted. That includes passing >>> it to memcpy. Even with a cast. >> >> So that means that I should use memcpy_fromio() even if the code if far >> less optimized. >> >> Shouldn't I re-implement some kind of IO copying function to deal with >> this IO memory so that I could take advantage of 8 words bursts? > > You could improve the IO memcpy/set etc implementations, which are > currently mostly unloved - I think that's a catch-22 which really needs > solving. They're not efficient because no one has taken the time to use > them, and everyone's avoiding them because they're not very efficient. > So, as no one's using them no one's motivated to improve them. Ok, so I use them in my following patch. And as a long-term exercise, I will try to have a look at those IO memcpy/set functions for ARM... Thanks for you advices, best regards, -- Nicolas Ferre