Re: [PATCH 1/9] ARM: dts: exynos: Add macros for GPIO configuration

Arnd Bergmann
2016-08-31T12:58:41Z

On Wednesday, August 31, 2016 2:53:02 PM CEST Krzysztof Kozlowski wrote:
> On 08/31/2016 02:42 PM, Arnd Bergmann wrote:
> > On Wednesday, August 31, 2016 2:13:25 PM CEST Krzysztof Kozlowski wrote:
> >>
> >> +#define PIN_PULL_NONE 0
> >> +#define PIN_PULL_DOWN 1
> >> +#define PIN_PULL_UP 3
> >> +
> >> +#define PIN_DRV_LV1 0
> >> +#define PIN_DRV_LV2 2
> >> +#define PIN_DRV_LV3 1
> >> +#define PIN_DRV_LV4 3
> >> +
> >> +#define PIN_FUNC_INPUT 0
> >> +#define PIN_FUNC_OUTPUT 1
> >> +#define PIN_FUNC_SPC_2 2
> >> +#define PIN_FUNC_SPC_3 3
> >> +#define PIN_FUNC_SPC_4 4
> >> +#define PIN_FUNC_SPC_5 5
> >> +#define PIN_FUNC_SPC_F 0xf
> >
> > Any reason for having a copy in each of those files instead of one
> > that is shared across all of them?
>
> The drive strengths differ between some of them. There are three groups
> of drive strengths:
> 1. Exynos3250, Exynos4 (all) and Exynos5250,
> 2. Exynos5260,
> 3. Exynos5410, 542x and 5800.

I see. That sounds like an even stronger reason to not duplicate
the definitions, as this is very confusing.

> Rest (functions and pull up/down) is the same so sharing the defines is
> possible but not that obvious. Solution would be for example adding a
> SoC-family prefix for PIN_DRV_LVx. Not that good...
>
> I could put it into three DTSI:
> - exynos3-pinctrl.dtsi (new file)
> - exynos5260-pinctrl.dtsi (like it is now)
> - exynos54xx-pinctrl.dtsi (new file)
>
> which would reduce the duplication. Other ideas?

I think having the soc-family prefix is better, as it avoids
defining the same symbol to a different value. Better make this
as explicit as possible.

I think overall, a better solution would have been to define the
constants globally (shared with non-exynos) to start with,
and have the driver translate generic numbers into vendor
specific ones. Obviously it's too late for that now.

Arnd