Re: [PATCH 1/4] dt-bindings: mmc: renesas_sdhi: Add r8a77470 support

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Wolfram,

On Mon, Sep 24, 2018 at 2:26 PM Wolfram Sang <wsa@the-dreams.de> wrote:
> > It seems RZ/G1C has two slighty different types of SD card interfaces:
> >   1. SDHI0 and SDHI2 use SYS-DMAC,
> >   2. SDHI1 can also be used as an MMC interface, and has an internal DMAC.
> >
> > Do we need to distinguish between them using the compatible value, or
> > are there other ways?
>
> Yes, that seems to need an update to our current implementation which is
> per-SoC only. One idea from my side would be to whitelist SYS-DMAC for
> this compatible and then check if dma-properties are present, otherwise
> fall back to internal DMAC?

I'm afraid that won't work, as the "dmas" properties are optional. So you
cannot distinguish between optional properties missing and internal DMA
present.

A dirty hack would be checking the device name for xxxxxxxx.sdhi, like how
whitelisting is implemented in the IPMMU driver.

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