From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Benjamin Herrenschmidt To: Dan Malek In-Reply-To: <99151309fed9dc6d9649e5e9a1299d6e@embeddededge.com> References: <1116984651.6395.60.camel@gaston> <99151309fed9dc6d9649e5e9a1299d6e@embeddededge.com> Content-Type: text/plain Date: Wed, 25 May 2005 15:15:39 +1000 Message-Id: <1116998140.6395.81.camel@gaston> Mime-Version: 1.0 Cc: linuxppc-dev list , linuxppc-embedded@ozlabs.org Subject: Re: RFC: Deprecating io_block_mapping List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2005-05-25 at 00:45 -0400, Dan Malek wrote: > On May 24, 2005, at 9:30 PM, Benjamin Herrenschmidt wrote: > > > As the subject says ... it's the source of endless headaches, is used > > in > > a way that often prevents moving TASK_SIZE freely, etc etc etc... > > Why are you so obsessed about this? :-) We all know what it does > and the limitations. If someone wants to use it in addition to other > kernel configuration options, their particular start up code will have > to be modified to accept this. We don't "all" know :) It's very easily misused... > > What are the good and unavoidable uses of it currently that cannot be > > replaced by some sort of ioremap ? > > > > (Note that if the answer to the above is: page tables exist too late, > > That's one reason. The other is to pin BATs or large page table entries > for more efficient access. True. > > .... I > > already have a reply: our initialisations happen too early, let's move > > things around so that ioremap is useable > > In most cases you can't do this. There are boards that have to map > serial ports for kgdb or early console debugging. How do they map ? pinning TLBs ? ioremap can do that... ioremap can be made to work very very early ... > There are also > boards that need access to local hardware registers to set up that > early. You may need to map a rom or some other non-volatile storage > to get some system parameters. Ok, well, it's really just requesting for comment here, I don't say I will kill it, just wondering ... Ben.