Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 25 May 2020 10:23:08 +0200 | Subject | Re: [PATCH 03/17] ARM: dts: r8a7742: Add I2C and IIC support |
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Hi Wolfram,
On Fri, May 22, 2020 at 10:17 PM Wolfram Sang <wsa+renesas@sang-engineering.com> wrote: > > > According to the Hardware User's Manual Rev. 1.00, the registers do exist > > > on all RZ/G1, except for RZ/G1E (see below). > > > > > > "(automatic transmission can be used as a hardware function, but this is > > > not meaningful for actual use cases)." > > > > > > (whatever that comment may mean?) > > Strange comment, in deed. Given the paragraph before, I would guess Gen1 > maybe had a "fitting" PMIC where SoC/PMIC handled DVFS kind of magically > with this automatic transfer feature? And Gen2 has not. > > > > On R-Car E3 and RZ/G2E, which have a single IIC instance, we > > > handled that by: > > > > > > The r8a77990 (R-Car E3) and r8a774c0 (RZ/G2E) > > > controllers are not considered compatible with > > > "renesas,rcar-gen3-iic" or "renesas,rmobile-iic" > > > due to the absence of automatic transmission registers. > > From a "describe the HW" point of view, this still makes sense to me. > Although, it is unlikely we will add support for the automatic > transmission feature (maybe famous last words).
;-)
> > > On R-Car E2 and RZ/G1E, we forgot, and used both SoC-specific and > > > family-specific compatible values. > > Okay, but we can fix DTs when they have bugs, or?
We can. But we also have to consider DT backwards compatibility: i.e. using an old DTB with a future kernel implementing the automatic transmission feature.
Fortunately R-Car E2 and RZ/G1E have SoC-specific compatible values, so we can easily blacklist it in the driver based on that. Blacklisting the last instance on the other SoCs is uglier, as it needs a quirk that checks both the SoC-compatible value and the absence of the generic compatible value. But it can still be done.
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> i.e. will queue in renesas-devel for v5.9.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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