On Thu, Nov 16, 2017 at 01:12:55PM +0100, Alan Martinovic wrote: > Hi, > I'm trying to modify a device tree to enable support of the second UART. > The actual device tree which is used for the example: > > https://github.com/getsenic/senic-os-linux/blob/senic/4.13/arch/arm/boot/dts/sun8i-h3-senic-hub.dts > > The device tree includes and overrides some additional files: > > #include "sun8i-h3.dtsi" > #include "sunxi-common-regulators.dtsi" > #include <dt-bindings/gpio/gpio.h> > #include <dt-bindings/input/input.h> > #include <dt-bindings/pinctrl/sun4i-a10.h> > > I would like to know to what does the extended device tree look like, > and use that as my base, because I don't really have the complete picture > by just looking at the sun8i-h3-senic-hub.dts > > In this example I'm interested in where are "uart0_pins_a" defined. > sun8i-h3-senic-hub.dts references them but has no definitions, > so I'm assuming the definition is somewhere in the included files. > > To help me out with this task I discovered the device tree decompiler. > Am expecting that the decompiled dts contains all the data that > end up in the dtb blob, and should, among other, contain all the information > available in sun8i-h3-senic-hub.dts. > > scripts/dtc/dtc -I dtb -O dts -o expanded-devtree.dts > arch/arm/boot/dts/sun8i-h3-senic-hub.dtb > > But the decompiled extended device tree also seems to have no > traces of "uart0_pins_a" at all : > > grep uart0_pins_a expanded-devtree.dts labels are purely a source level construct (though overlays changes that some) and are lost after compiling. You have to look for 'uart0@0'. > > I've also discovered the hidden .tmp files: > > ⟫ ls arch/arm/boot/dts/.sun8i-h3-* > arch/arm/boot/dts/.sun8i-h3-senic-hub.dtb.cmd > arch/arm/boot/dts/.sun8i-h3-senic-hub.dtb.d.dtc.tmp > arch/arm/boot/dts/.sun8i-h3-senic-hub.dtb.d.pre.tmp > arch/arm/boot/dts/.sun8i-h3-senic-hub.dtb.dts.tmp > > and in one of them there is a definition to "uart0_pins_a": > > ⟫ grep uart0_pins_a arch/arm/boot/dts/.sun8i-h3-* > arch/arm/boot/dts/.sun8i-h3-senic-hub.dtb.dts.tmp: uart0_pins_a: uart0@0 { > arch/arm/boot/dts/.sun8i-h3-senic-hub.dtb.dts.tmp: pinctrl-0 = > <&uart0_pins_a>; > > My question is, which one is a more accurate representation > of the final device tree that I should use as a basis? Compiling dts to dts is mainly useful to get rid of all the C preprocessor and includes to see what the final nodes look like. You do lose some things though. > Why isn't it correct to expect that everything from sun8i-h3-senic-hub.dts > will end up in the final device tree blob? That's true for every compiler. After compiling, preprocessor symbols are gone, functions may be inlined, etc. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
