On Wednesday, October 19, 2016 10:10:38 AM CEST Geert Uytterhoeven wrote: > Hi Arnd, > > On Mon, Oct 10, 2016 at 4:28 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Tuesday, October 4, 2016 11:09:23 AM CEST Geert Uytterhoeven wrote: > >> Some Renesas SoCs may exist in different revisions, providing slightly > >> different functionalities (e.g. R-Car H3 ES1.x and ES2.0). This needs to > >> be catered for by drivers and/or platform code. The recently proposed > >> soc_device_match() API seems like a good fit to handle this. > >> > >> This patch series implements the core infrastructure to provide SoC and > >> revision information through the SoC bus for Renesas ARM SoCs. It > >> consists of 4 patches: > >> - Patch 1 avoids a crash when SoC revision information is needed and > >> provided early, > >> - Patch 2 (from Arnd) introduces the soc_device_match() API. > >> I don't know if, when, and through which channel this patch is > >> planned to go upstream, > >> - Patch 3 fixes a bug in soc_device_match(), causing a crash when > >> trying to match on an SoC attribute that is not provided (seen on > >> EMEV2, RZ/A, and R-Car M1A, which lack revision information), > >> - Patch 4 identifies Renesas SoCs and registers them with the SoC bus. > >> > >> Tested on (family, machine, soc_id, optional revision): > >> > >> Emma Mobile EV2, EMEV2 KZM9D Board, emev2 > >> RZ/A, Genmai, r7s72100 > >> R-Mobile, APE6EVM, r8a73a4, ES1.0 > >> R-Mobile, armadillo 800 eva, r8a7740, ES2.0 > >> R-Car Gen1, bockw, r8a7778 > >> R-Car Gen1, marzen, r8a7779, ES1.0 > >> R-Car Gen2, Lager, r8a7790, ES1.0 > >> R-Car Gen2, Koelsch, r8a7791, ES1.0 > >> R-Car Gen2, Gose, r8a7793, ES1.0 > >> R-Car Gen2, Alt, r8a7794, ES1.0 > >> R-Car Gen3, Renesas Salvator-X board based on r8a7795, r8a7795, ES1.0 > >> R-Car Gen3, Renesas Salvator-X board based on r8a7796, r8a7796, ES1.0 > >> SH-Mobile, KZM-A9-GT, sh73a0, ES2.0 > > > > As mentioned in the comment for the driver patch, I think this makes > > a lot of sense for the machines that have a revision register, in > > particular when the interpretation of that register is always done > > the same way, but I'm a bit skeptical about doing it in the same driver > > for machines that don't have the register. > > > > Matching by a device rather than the SoC platform also has the advantage > > that there is no need to maintain a list of compatible numbers in the > > driver. > > Currently we (usually) use: > - SoC-specific compatible values, to handle known differences within the > same family now, and handle future unknown differences, > - Family-specific compatible values, which we define ourselves. > > Usually drivers match on the latter. > > Every time a new SoC is introduced, we have to update lots of DT binding > docs, to add the new SoC-specific compatible values. > > Two-phase matching (driver code matches against "renesas,<foo>", > driver matches against SoC using soc_device_match()) would allow to > remove the burden of updating DT documentation all the time. > The drivers would need updates, though. > Another advantage would be that we can reuse .dtsi snippets for SoCs in > the same family, which we currently can't easily do due to the SoC-specific > compatible values. Interesting idea, but unrelated to my comment above, which was about the soc driver in particular, rather the drivers using it. Arnd -- 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
