On Mon, Oct 19, 2020 at 2:06 PM Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> wrote:
> From: Phong Hoang <phong.hoang.wz@xxxxxxxxxxx>
>
> Add support for the R-Car V3U (r8a779a0) SoC.
> This includes support for the new "General Input Enable" register to
> control input enable.
>
> Signed-off-by: Phong Hoang <phong.hoang.wz@xxxxxxxxxxx>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---
> Untested on actual hardware.
>
> Should input be enabled unconditionally, as recommended by the Hardware
> Manual for backwards compatibility with existing software?
> As per (errata?) commit ae9550f635533b1c ("gpio-rcar: Use OUTDT when
> reading GPIOs configured as output"), the gpio-rcar driver does not use
> the INDT register to read the status of a GPIO line when configured for
> output.
More investigation:
1. On SH7734, R-Car Gen1, R-Car Gen2, and RZ/G1, INDT only reflects
the state of the input pin if the GPIO is configured for input
(documented, verified on R-Car M2-W),
2. On R-Car Gen3 and RZ/G2, INDT always reflects the state of the
input pin (documented, verified on R-Car H3/M3-W/M3-N),
3. On R-Car V3U, input enable can be configured explicitly through the
new INEN register (documented, unverified).
Given register accesses are slow, I think it makes sense to enable input
explicitly and unconditionally on R-Car V3U, and always use INDT to read
pin state on R-Car Gen3 and V3U.
Thanks for your comments!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
