Re: [PATCH v3 0/4] fix memremap on ARM

[Brian Norris <computersforpeace@gmail.com>]

On Fri, Mar 04, 2016 at 08:16:56PM +0100, Ard Biesheuvel wrote:
> On 4 March 2016 at 19:34, Dan Williams <dan.j.williams@intel.com> wrote:
> > On Fri, Mar 4, 2016 at 1:48 AM, Ard Biesheuvel
> > <ard.biesheuvel@linaro.org> wrote:
> >> This is something I ran into while working on support for the UEFI
> >> memory attributes and ESRT tables. In both cases, these tables are
> >> passed to the kernel in memory which is guaranteed to be below 4 GB,
> >> but may be outside of the kernel direct mapping. (UEFI typically
> >> attempts to allocate from the top down, which means such tables are
> >> highly likely to be in highmem for any system with more than 760 MB
> >> of system RAM)
> >>
> >> The recently introduced memremap() is a very useful abstraction for
> >> accessing such tables, because it is generic, and already attempts to
> >> do the right thing with respect to regions that may already have been
> >> mapped directly. However, it falls back to ioremap_cache() for mapping
> >> high memory, which is not allowed on ARM for system RAM, and also results
> >> in the region to be mapped with different attributes depending on whether
> >> it is covered by lowmem or not.
> >>
> >> So instead, create an arch specific hook 'arch_memremap_wb(), and
> >> implement it for ARM using the same memory attributes used for the
> >> linear mapping. Note that memremap will only call this hook for regions
> >> that are not already mapped permanently.
> >>
> >> Since this change results in memremap() to use attributes different from
> >> the ones used by ioremap_cache(), revert the change to pxa2xx-flash that
> >> moved it to memremap.
> >>
> >> Changes since v2:
> >> - add patch to bring back ioremap_cached() on ARM
> >> - switch pxa2xx-flash back to ioremap_cached() not ioremap_cache()
> >> - use arch_ioremap_caller not __arm_ioremap_caller() in patch #4
> >> - deal with __iomem annotation of arch_ioremap_caller (patch #4)
> >>
> >> Changes since v1/rfc:
> >> - new patch #1 that reverts the ioremap_cache->memremap conversion for the
> >>   pxa2xx-flash driver
> >> - added Dan's ack to patch #2
> >>
> >> Ard Biesheuvel (4):
> >>   ARM: reintroduce ioremap_cached() for creating cached I/O mappings
> >>   mtd: pxa2xx-flash: switch back from memremap to ioremap_cached
> >>   memremap: add arch specific hook for MEMREMAP_WB mappings
> >>   ARM: memremap: implement arch_memremap_wb()
> >>
> >>  arch/arm/include/asm/io.h       | 12 ++++++++++++
> >>  arch/arm/mm/ioremap.c           | 16 ++++++++++++++--
> >>  drivers/mtd/maps/pxa2xx-flash.c |  6 +++---
> >>  kernel/memremap.c               | 11 ++++++++---
> >>  4 files changed, 37 insertions(+), 8 deletions(-)
> >>
> >
> > For the series:
> >
> > Acked-by: Dan Williams <dan.j.williams@intel.com>
> 
> Thanks Dan,
> 
> With the added patch #1, I think it now makes the most sense for
> Russell to take the whole series via the ARM tree.
> 
> @Brian, David: any objections?

Nope. For the MTD part:

Acked-by: Brian Norris <computersforpeace@gmail.com>

Regards,
Brian