Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 18 May 2020 12:10:05 +0200 | Subject | Re: [PATCH 03/17] ARM: dts: r8a7742: Add I2C and IIC support |
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Hi Wolfram,
On Mon, May 18, 2020 at 11:26 AM Wolfram Sang <wsa+renesas@sang-engineering.com> wrote: > > > However, both versions (with and without automatic transmission) are > > > described with the same "renesas,iic-r8a7742" compatible. Is it possible > > > to detect the reduced variant at runtime somehow? > > > > > I couldn't find anything the manual that would be useful to detect at runtime.
Hence if we really need that (see below), we need a quirk based on compatible value + base address.
> > > My concern is that the peculiarity of this SoC might be forgotten if we > > > describe it like this and ever add "automatic transmissions" somewhen. > > > > > Agreed. > > Well, I guess reading from a register which is supposed to not be there > on the modified IP core is too hackish.
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?)
> Leaves us with a seperate compatible entry for it?
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.
On R-Car E2 and RZ/G1E, we forgot, and used both SoC-specific and family-specific compatible values.
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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