From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from an-out-0708.google.com (an-out-0708.google.com [209.85.132.250]) by ozlabs.org (Postfix) with ESMTP id 85218DDFA7 for ; Thu, 7 Aug 2008 07:54:52 +1000 (EST) Received: by an-out-0708.google.com with SMTP id c34so22983anc.78 for ; Wed, 06 Aug 2008 14:54:50 -0700 (PDT) Message-ID: Date: Wed, 6 Aug 2008 15:54:50 -0600 From: "Grant Likely" Sender: glikely@secretlab.ca To: "Kumar Gala" Subject: Re: [RFC/PATCH 1/3] powerpc: add ioremap_bat() function for setting up BAT translated IO regions. In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <20080806055214.30717.86092.stgit@trillian.secretlab.ca> <20080806060223.30717.35175.stgit@trillian.secretlab.ca> Cc: linuxppc-dev@ozlabs.org, paulus@samba.org, miltonm@bga.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Aug 6, 2008 at 8:07 AM, Kumar Gala wrote: > > On Aug 6, 2008, at 1:02 AM, Grant Likely wrote: > >> From: Grant Likely >> >> ioremap_bat() is useful for things like mapping SoC internally memory >> mapped >> register and early text because it allows mappings to devices to be setup >> early in the boot process where they are needed, and the mappings persist >> after the MMU is configured. >> >> Without ioremap_bat(), setting up the MMU would cause the early text >> mappings to get lost and mostly likely result in a kernel panic on the >> next >> attempt at output. >> >> Signed-off-by: Grant Likely >> --- > > why can't we just do this in ioremap itself? I suppose we could; but the usecase is somewhat different and I wanted to keep it simple. Using a separate API also helps reenforce that the caller really needs to know what they are doing because BATs are a limited resource. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.