On Thu, Apr 19, 2018 at 1:49 AM, Tero Kristo <t-kristo@xxxxxx> wrote: > On 19/04/18 03:19, Rob Herring wrote: >> >> On Tue, Apr 17, 2018 at 4:10 AM, Tero Kristo <t-kristo@xxxxxx> wrote: >>> >>> The AM57xx-evm is an overlay on top of beagle-x15 board. This contains >>> a display extension macro, and a few extra peripherals. Two versions >>> of the evm are supported, the base evm and the latest rev A3 evm. A >>> common overlay file is used for both boards. >>> >>> Signed-off-by: Tero Kristo <t-kristo@xxxxxx> >>> --- >>> arch/arm/boot/dts/ti/am57xx-evm-common.dtso | 175 >>> ++++++++++++++++++++++++++++ >> >> >> Why do this as an overlay? To what level is an AM57xx-evm functional >> using a beagle-x15 dtb? > > > Basically, am57xx-evm is just a beagle-x15 with an extension board > physically plugged into it. If you don't add the am57xx-evm overlay, display > (+ WLAN + some gpios) obviously don't work, but rest of the functionality > does. > > If you have an am57xx-evm, you can also unplug the extension board to get a > plain beagle-x15 board as I did, I don't typically care about things like > display / WLAN in my work. Okay, makes sense, but the naming convention doesn't really convey these details. I guess users of the boards would understand this. >>> arch/arm/boot/dts/ti/am57xx-evm-reva3.dtso | 11 ++ >>> arch/arm/boot/dts/ti/am57xx-evm.dtso | 11 ++ >> >> >> I think I'd structure this as just the A3 is an overlay. Applying it >> will override everything in am57xx-evm.dtso, so what's the point to >> making users of both board variations apply an overlay. Plus, you >> could have only known the differences in the board revisions after you >> had both boards. That wouldn't work if you developed this as new >> boards appear. > > > Well, beagle-x15 is still the base board for both, and different revisions > of those also. The changes are relatively minor, but they are there. But > yes, different hierarchies for these could be applied. My point is that if you have 2 revisions of a given board, at some point in time there was only 1 revision of that board. So you have a dtb for that revision. Then a new revision comes out. You should not be refactoring the existing dtbs based on what changed in the new revision such that you have the common bits, rev 1 overlay and rev 2 overlay. Instead, make a rev 1 to rev 2 overlay. Now if you have 2 different revisions in parallel that's a different story. For example, if the beagle-x15 is stuffed differently for use with the EVM vs. standalone. 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
