From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH] drm/i915: swizzling support for snb/ivb Date: Mon, 6 Feb 2012 17:06:04 +0100 Message-ID: <20120206160604.GC4066@phenom.ffwll.local> References: <1328138138-6143-1-git-send-email-daniel.vetter@ffwll.ch> <20120202053057.GA13722@seagal.kumite> <20120202084001.GA4107@phenom.ffwll.local> <4F2DF3E5.80309@bwidawsk.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-we0-f177.google.com (mail-we0-f177.google.com [74.125.82.177]) by gabe.freedesktop.org (Postfix) with ESMTP id 0E9A79E83C for ; Mon, 6 Feb 2012 08:05:55 -0800 (PST) Received: by wera10 with SMTP id a10so5675934wer.36 for ; Mon, 06 Feb 2012 08:05:55 -0800 (PST) Content-Disposition: inline In-Reply-To: <4F2DF3E5.80309@bwidawsk.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Ben Widawsky Cc: Daniel Vetter , Intel Graphics Development List-Id: intel-gfx@lists.freedesktop.org On Sat, Feb 04, 2012 at 07:13:41PM -0800, Ben Widawsky wrote: > On 02/02/12 00:40, Daniel Vetter wrote: > >On Wed, Feb 01, 2012 at 09:30:57PM -0800, Ben Widawsky wrote: > >[...] > >>I'd also say it's not a bad idea to elaborate the assumption that we > >>never have less than 256MB of memory WARN_ON(dimm_c0 + dimm_c1 == 0). > > > >I'm pretty sure that we can't boot with 0mb of ram ;-) The other thing is > >that swizzling is a pure preformance optimization - if we enable it on > >setup where it's not required we'll only annoy the memory controller with > >less efficient access patterns. > > What I meant was, this value is still 0 in say, a system with 2 > 128MB DIMMs. Well, I have a feeling that 256mb is the smallest size for a ddr3 dimm. But I'm a bit too lazy to check that (and frankly wouldn't know where). Furthermore swizzling on gen6+ is afaics just a performance thing and should never affect correctness, so even if 128mb dimms exist I think we can just not care - performance isn't gonna be stellar anyway ;-) -Daniel -- Daniel Vetter Mail: daniel@ffwll.ch Mobile: +41 (0)79 365 57 48