From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rproxy.gmail.com (rproxy.gmail.com [64.233.170.205]) by ozlabs.org (Postfix) with ESMTP id 9C64167B44 for ; Fri, 10 Jun 2005 09:25:40 +1000 (EST) Received: by rproxy.gmail.com with SMTP id g11so184563rne for ; Thu, 09 Jun 2005 16:25:39 -0700 (PDT) Message-ID: <61cc712d050609162565d8bbfd@mail.gmail.com> Date: Thu, 9 Jun 2005 16:25:39 -0700 From: Kylo Ginsberg To: Kumar Gala In-Reply-To: <815f92995891b6f6e5333d0658637788@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <61cc712d0506091509527ee680@mail.gmail.com> <815f92995891b6f6e5333d0658637788@freescale.com> Cc: linuxppc-embedded@ozlabs.org Subject: Re: Mapping full 1 GB of memory on a Freescale Book E part Reply-To: Kylo Ginsberg List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 6/9/05, Kumar Gala wrote: >=20 > On Jun 9, 2005, at 5:09 PM, Kylo Ginsberg wrote: > > I've modified fsl_booke_mmu.c to use a 4th TLB, thus mapping the full > > 1 GB of memory. However, I'm new to linux memory management, so I'd > > appreciate any comments as to whether there are tradeoffs or dangers > > here that I am missing. >=20 > There is a danger here in that you have left no virtual address space > for the kernel. Since KERNEL_BASE is normally 0xc000_0000 + 1G ends up > a the end of memory. There for any devices that need virtual memory > space would not have any to map out of. I'm kinda amazed this works at > all. I'd be interested in seeing what a boot log looks like for this > config. Sorry, should have mentioned this in the first post. I dropped KERNEL_BASE to 0xa0000000 and upped LOWMEM_SIZE to 0x40000000. So the Advanced Setup portion of my .config reads: # # Advanced setup # CONFIG_ADVANCED_OPTIONS=3Dy CONFIG_HIGHMEM_START=3D0xfe000000 CONFIG_LOWMEM_SIZE_BOOL=3Dy CONFIG_LOWMEM_SIZE=3D0x40000000 CONFIG_KERNEL_START_BOOL=3Dy CONFIG_KERNEL_START=3D0xa0000000 # CONFIG_TASK_SIZE_BOOL is not set CONFIG_TASK_SIZE=3D0x80000000 # CONFIG_BOOT_LOAD_BOOL is not set CONFIG_BOOT_LOAD=3D0x00800000 and under Platform Options: # CONFIG_HIGHMEM is not set > The way to handle this is by enabling HIGHMEM support in the kernel or > dropping the KERNEL_START in the config. I'm haven't ever tried to > drop KERNEL_START so your milage may very on what if anything that will > break. So, an alternative would be to leave fsl_booke_mmu.c untouched, revert my KERNEL_START/LOWMEM mods, and instead enable HIGHMEM? Setting HIGHMEM_START to ...? Will that entail more TLB thrashing? Kylo