Re: [GIT PULL 2/2] SoCFPGA update for v4.13

[Arnd Bergmann <arnd@xxxxxxxx>]

On Fri, Jun 23, 2017 at 2:28 PM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Fri, Jun 23, 2017 at 2:03 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
>> On Wed, Jun 21, 2017 at 5:35 PM, Dinh Nguyen <dinguyen@xxxxxxxxxx> wrote:
>>> Hi Arnd, Kevin, and Olof:
>>>
>>> Please pull in this SoCFPGA Kconfig update for v4.13.
>>
>> I'd like to defer this one until I hear back from the GPIO maintainers:
>>
>> With this patch, CONFIG_ARCH_NR_GPIO increases from 1024 to 2048
>> in the ARM defconfig build. Is this ok in terms of runtime overhead?
>
> There is no problem with runtime overhead, only with footprint.
>
> The array of sizeof(gpio_desc) increases to double.
>
> struct looks like so:
>
> struct gpio_desc {
>         struct gpio_device      *gdev;
>         unsigned long           flags;
>         const char              *label;
>         const char              *name;
> };
>
> Looks like 4x32 bits in most cases, so this means a 4*4*1024 =
> 16 KiB footprint increase.

Ok.

> We have had to allocate this statically because so many playforms still
> use the legacy GPIO API.
>
>> If not, are there any alternatives?
>
> Not really, if they have this many GPIOs.

Right. I pulled the branch into next/soc now, thanks for the quick reply!

> Helping out ridding the kernel of users of the old GPIO global
> numberspace ABI is appreciated though.

I guess there is no easy way to figure out which drivers are needed on
socfpga and do those first, right?

        Arnd
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