From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Thu, 1 Dec 2011 11:57:18 +0100 Subject: flatmem broken for nommu? [Was: Re: does non-continuous RAM means I need to select the sparse memory model?] In-Reply-To: References: <20111129203010.GA26618@pengutronix.de> Message-ID: <20111201105718.GJ26618@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Nov 29, 2011 at 10:39:10PM -0200, Fabio Estevam wrote: > Hi Uwe, > > 2011/11/29 Uwe Kleine-K?nig : > > Hello, > > > > I'm currently working on a new arch port and my current machine has RAM > > at 0x10000000 and 0x80000000. So there is a big hole between the two > > banks. When selecting the sparse memory model it works, but when > > selecting flat the machine runs into a BUG in mark_bootmem() called by > > free_unused_memmap() to free the space between the two banks. > > My understanding is that you have to select ARCH_HAS_HOLES_MEMORYMODEL. I think that is not necessary. > > Is that expected (meaning I cannot use the flat model)? I currently > > don't have another machine handy that has >1 memory back to test that. > > In case you have access to a MX35PDK you can try on this board as it does have > the memory hole. No I havn't, but I just used a 128MB machine and changed that in the .fixup callback to 64MB + 32MB with a 32MB hole in between and it works fine without ARCH_HAS_HOLES_MEMORYMODEL. I debugged the problem a bit further and one symptom is that struct page *mem_map is NULL for me. That looks wrong. I guess this is just broken for nommu. I will dig into that later today. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |