From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Tue, 22 Nov 2016 11:17:52 +0100 Subject: [RFC PATCH 11/11] ARM: Allow ARCH_MULTIPLATFORM to be selected for NOMMU In-Reply-To: <1479806768-39911-12-git-send-email-vladimir.murzin@arm.com> References: <1479806768-39911-1-git-send-email-vladimir.murzin@arm.com> <1479806768-39911-12-git-send-email-vladimir.murzin@arm.com> Message-ID: <16587553.f9R1mxJih5@wuerfel> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tuesday, November 22, 2016 9:26:08 AM CET Vladimir Murzin wrote: > With this patch applied potentially any platform can be built in NOMMU > configurations if CONFIG_EXPERT is selected. However, there is no > guaranty that platform can successfully run such Image. So the main > motivation behind of this patch: > - bring build coverage for NOMMU configurations > - allow known working NOMMU platforms (like R-class) to be used > - pave a way to add support for single address space (aka 1:1 mapping) > for MMU platforms, so they can be usable in NOMMU configurations > > Cc: Hartley Sweeten > Cc: Ryan Mallon > Cc: Tony Lindgren > Cc: Thierry Reding > Cc: Russell King > Signed-off-by: Vladimir Murzin I'd have to give this a spin with my randconfig build setup, I'd rather not introduce build regressions. Have you tried an allmodconfig build with CONFIG_MMU disabled? Can you provide a git tree that I can try pulling in? Another question is what architecture levels and what platforms we want to support without MMU. The only ARMv4/v5 platform we still have that can actually use NOMMU cores is Integrator with its ARM7TDMI, ARM920T and ARM966E core tiles (and possibly others I couldn't immediately find). Do we actually care about them any more now that all the NOMMU world is ARMv7-M? Are there any benefits in running an ARM920T or ARM926E core with MMU disabled, and does this work with your patches? If not, we could limit it to ARMv7-A/R and possibly ARMv6. Depending on how the build tests go, a per-platform opt-in might be easier than having an opt-out for things that don't work. Arnd