From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: John Bonesio To: "Grant Likely" Subject: Re: ppc440 caches - change proposal [RFC] Date: Wed, 9 Apr 2008 11:00:40 -0700 References: <20080408225329.5EC171A8007D@mail11-dub.bigfish.com> <1207695415.14711.11.camel@pasglop> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Message-Id: <20080409180042.511531370055@mail134-sin.bigfish.com> Cc: Linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Grant, I have a question about your patch. It appears as if the cache setup code is in a file that would be used only on Xilinx FPGA devices. I understand that many people are using a bootloader that already sets up the cache for the kernel, but I'm wondering if Xilinx boards are really a special case, or if there may be other non-Xilinx related systems that would also not be using a bootloader. I also understand the desire to avoid code that does the same work more than once, but I wonder if in this case, it's creating too strong a dependence on the specific behavior of a certain bootloader. I also wonder if arch/powerpc is being made more complex by trying to split out this code change into a Xilinx specific area, when the change could just be rolled into head_40x.S and we could do away with virtex405-head.S. Just some thoughts, - John On Tuesday 08 April 2008 16:15, you wrote: > On Tue, Apr 8, 2008 at 4:56 PM, Benjamin Herrenschmidt > wrote: > > > > On Tue, 2008-04-08 at 15:53 -0700, John Bonesio wrote: > > > I was thinking it might be good to have the kernel initialize these > > > cache control registers in it's own start up code. Or perhaps this > > > could be done in the kernel's simple bootloader. We could probably put > > > this change in a Xilinx specific startup file, but this change doesn't > > > seem specific to Xilinx FPGA boards. > > > > The kernel's wrapper would be a good place to put that I suspect. That's > > the kind of thing that should be provided as a "library" function to be > > optionally called by platform code. Either in the wrapper or the main > > kernel platform code. > > Code is already queued up for 2.6.26 to do exactly this on ppc405 > virtex platforms. We can do the same thing for 440. Look at > virtex405-head.S in the following patch: > > http://patchwork.ozlabs.org/linuxppc/patch?person=486&id=17410 > > Cheers, > g. > > > -- > Grant Likely, B.Sc., P.Eng. > Secret Lab Technologies Ltd. > >