From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Fri, 19 Feb 2016 16:59:43 +0100 Subject: [PATCH] ARM: Allow MULTIPLATFORM to select XIP In-Reply-To: References: <1455816310-11308-1-git-send-email-chris.brandt@renesas.com> <3699765.F7sfuMCyKT@wuerfel> Message-ID: <64215923.Y25jP5YYZ2@wuerfel> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Friday 19 February 2016 15:36:23 Chris Brandt wrote: > On 19 Feb 2016, Arnd Bergmann wrote: > > > For PHYS_OFFSET, parsing the DT doesn't help at all because we only > > need it for XIP_KERNEL (more or less at least) which cannot patch > > the kernel image at boot time, so knowing that the address is wrong > > also doesn't help you. > > > > Arnd > > OK, at first I was thinking that PHYS_OFFSET was only used early in boot as a pointer to valid RAM before the DT was read (in head.S and head-nommu.S). Hence, you could pass in the pointer in via another CPU register like the DT pointer is passed in. > > But, now I see that PHYS_OFFSET is used all over the place as a hard coded #define, hence your comment "which cannot patch the kernel image at boot time" > > So, I retract my thought...it has to be configured at build-time (unless of course you turn it into a global variable everywhere...which might be an even bigger mess) > BTW, I've tried removing the patching in CONFIG_PHYS_VIRT and replaced it with references to __pv_phys_pfn_offset, which surprisingly only grew .text from 4901692 to 4904300 bytes, so the size overhead of doing this would be close to zero. Arnd