From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aneesh V Date: Mon, 25 Jun 2012 14:49:27 -0700 Subject: [U-Boot] [PATCH] arm: enable unaligned access on ARMv7 In-Reply-To: <20120625223445.257fef5c@lilith> References: <1338918451-10126-1-git-send-email-dev@lynxeye.de> <4FCE52FB.3020501@wwwdotorg.org> <1338923180.1377.2.camel@tellur> <20120622111501.21e1fdcc@aari01-12> <1340357816.1381.21.camel@tellur> <20120622131654.2c694a82@aari01-12> <1340365637.1381.38.camel@tellur> <4FE4ED98.2030103@ti.com> <4FE4EE13.7040206@ti.com> <20120623110113.511091c8@lilith> <20120625223445.257fef5c@lilith> Message-ID: <4FE8DCE7.7090700@ti.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Albert, On 06/25/2012 01:34 PM, Albert ARIBAUD wrote: > Hi Aneesh, > >>>> BTW, I agree that enabling un-aligned access is not a bad idea. >>> >>> Just being "not a bad idea" is not enough for me to accept this. It >>> will have to be the sole sound solution to a problem, and at this >>> point, I do not think it is as far as USB structure mis-alignement >>> issues are concerned. >> >> My point is that enabling un-aligned accesses in itsown merit >> is not a bad idea, not as a solution to this problem. I have seen >> it being enabled in HLOS environment. TI's Symbian port for >> instance had it enabled for OMAP3. I don't >> know why Linux too shoudln't take advantage of such hw >> features. Perhaps you don't want to take it at this point of time to >> force the real solution to the USB problem, which is reasonable. > > What is the (non-contrived) problem to which allowing mis-aligned > accesses would be a solution? memcpy() when there is a mismatch in the alignment of source and destination buffers. Let's say the source buffer is 4 byte aligned but the destination buffer is only 2 byte aligned. I believe relaxed alignment requirements will help in writing an accelerated memcpy routine for this case. Again, my point is that as a platform software provider I would like to enable such features to make maximum things work on my platform, where as the developer of a generic sw module should probably avoid depending on such features to ensure maximum portability. br, Aneesh