[PATCH] PCI: generic: map config window in one go

[Ard Biesheuvel]

On 29 January 2016 at 15:52, Arnd Bergmann <arnd at arndb.de> wrote:
> On Friday 29 January 2016 15:32:01 Ard Biesheuvel wrote:
>> On 29 January 2016 at 15:28, Will Deacon <will.deacon at arm.com> wrote:
>> > Hi Ard,
>> >
>> > On Fri, Jan 29, 2016 at 03:17:15PM +0100, Ard Biesheuvel wrote:
>> >> Instead of iterating over the PCI config window and performing individual
>> >> ioremap() calls on all the adjacent slices, perform a single ioremap() to
>> >> map the entire region, and divvy it up later. This not only prevents
>> >> leaving some of it mapped if we fail half way through, it also ensures that
>> >> archs that support huge-vmap can use section mappings to perform the
>> >> mapping.
>> >>
>> >> On my Seattle A0 box, this transforms 128 separate 1 MB mappings that are
>> >> mapped down to 4 KB pages into a single 128 MB mapping using 2 MB sections,
>> >> saving 512 KB worth of page tables.
>> >>
>> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> >> ---
>> >
>> > The code was written this way in response to feedback during driver review
>> > that we couldn't necessarily grab that much contiguous vmalloc space on
>> > 32-bit ARM. Unless that's changed, we probably want to to predicate this
>> > change on having a 64-bit arch.
>> >
>>
>> Ah right. How about testing for the ARCH_HAVE_HUGE_VMAP Kconfig symbol
>> explicitly?
>>
>
> Testing for 64BIT should be sufficient.
>

Does it make sense to spin a v2 for this patch? Given the discussion
we had regarding allocating only the config regions for busses that
are populated, perhaps there is a better approach here?