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

[Ard Biesheuvel]

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?