From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 7EED61007D3 for ; Thu, 26 Nov 2009 03:53:19 +1100 (EST) Message-ID: <49400.84.105.60.153.1259167993.squirrel@gate.crashing.org> In-Reply-To: <4B0C701F.1040101@yahoo.es> References: <1258927311-4340-1-git-send-email-albert_herranz@yahoo.es> <1258927311-4340-2-git-send-email-albert_herranz@yahoo.es> <1258927311-4340-3-git-send-email-albert_herranz@yahoo.es> <1258927311-4340-4-git-send-email-albert_herranz@yahoo.es> <4B0C1A25.8030401@yahoo.es> <4B0C701F.1040101@yahoo.es> Date: Wed, 25 Nov 2009 17:53:13 +0100 (CET) Subject: Re: [RFC PATCH 03/19] powerpc: gamecube: bootwrapper bits From: "Segher Boessenkool" To: "Albert Herranz" MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Cc: linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , >>>> WIMG=0000, are you sure? Not M=1? >>> >>> To be honest, I don't recall the details now. >>> But it was tested in the very early days, the result was not the >>> expected one and, in the end, manual cache coherency management was >>> still needed. >> >> Sure, the memory controllers don't do coherency. I'm slightly worried >> about two things: >> 1) Will the generic code use M=0 as well? Is it a problem if it >> doesn't? >> 2) Do lwarx. etc. work in M=0? >> >> And a question: does M=0 actually give better performance (lower bus >> utilisation, and maybe saves a few cycles)? > > I think that the generic code uses M=0 _except_ for SMP and some platforms > (see comment in cputable.h). > And yes, the generic code works with these processors :) I meant, if it doesn't, does it give conflicts. But I did some reading up and M=0 is indeed the way to go, so all is fine :-) > M=0 should have a lower bus utilization, yes. > Also M=0 is a requirement if you use some Gekko/Broadway features like the > locked (half-)cache. Well we don't use that, but point taken. Segher