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 252DFDDFD1 for ; Thu, 7 Aug 2008 08:17:04 +1000 (EST) Message-Id: <75A0A752-FF2C-41B6-A6D3-E510E8FD4E91@kernel.crashing.org> From: Kumar Gala To: Grant Likely In-Reply-To: Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Mime-Version: 1.0 (Apple Message framework v926) Subject: Re: [RFC/PATCH 1/3] powerpc: add ioremap_bat() function for setting up BAT translated IO regions. Date: Wed, 6 Aug 2008 17:11:36 -0500 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 Aug 6, 2008, at 4:54 PM, Grant Likely wrote: > 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. there is a bunch of error checking and difference in semantics that you need to fix. I think introduce a new API for this is silly, especially since we expect there to only be one actual invocation of the API for serial console access. - k