On Sat, May 19, 2018 at 11:52 AM, Christian Lamparter <chunkeey@xxxxxxxxx> wrote: > On Friday, May 18, 2018 7:18:26 AM CEST Bjorn Andersson wrote: >> > + gpio-ranges = <&msmgpio 0 0 150>; >> >> I'm still confused to why this information is in DT at all, it feels >> like an implementation detail, not a system configuration thing. This reflects especially the layout of systems such as HiSilicon that have a standard fit-all pin controller (pinctrl-single.c, shared with OMAP) and a standard PL061 GPIO primecell from ARM (gpio-pl061.c) shared with many other SoCs. These are non-HiSilicon-specific drivers used in other SoCs. So the ranges in e.g. arch/arm64/boot/dts/hisilicon/hi6220.dtsi define how the pin controller and the GPIO blocks inside the SoC are connected using these ranges. So "system configuration" is something different for you guys than for HiSilicon. They need to configure how the stuff inside the SoC are wired up, because they are using standard silicon used in other SoCs. As I understand it, your SoCs are so Qualcomm-specific and idiomatic that this situation never happened to you :) > I did look at the commits and code from back in 2013. From what > I can gather "this implementation detail" was realized the way > it is now, because "devicetree was the new thing" and it seemed > like a good idea to make it as extendable/generic as possible. Many mistakes were made when shoehorning device tree into the ARM architecture with one finger constantly on the fast-forward button. There were reasons for this. Mea culpa. I hope to fix them all before I retire. One use case (which still applied) are pin controllers and GPIO chips defined through the use of platform data. If we have for example a PCI card with a pin controller and GPIO block (Alessandro Rubini ran into such a device at CERN IIRC) we need to be able to define both components and connect them using ranges, even without either device tree or ACPI hardware descriptions. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
