Re: [PATCH RFC] hw/sh4/sh7750: Add STBCR/STBCR2 register support

[Geert Uytterhoeven]

Hi Sato-san,

On Thu, Oct 19, 2023 at 4:03 AM Yoshinori Sato
<ysato@users.sourceforge.jp> wrote:
> On Wed, 18 Oct 2023 21:40:23 +0900,
> Geert Uytterhoeven wrote:
> > The new Linux SH7750 clock driver uses the registers for power-down
> > mode control, causing a crash:
> >
> >     byte read to SH7750_STBCR_A7 (0x000000001fc00004) not supported
> >     Aborted (core dumped)
> >
> > Fix this by adding support for the Standby Control Registers STBCR and
> > STBCR2.
>
> FRQCR is also not returning the correct value, so it needs to be fixed.

I knew there would be more, hence the RFC ;-)

> Here are my changes.
> https://gitlab.com/yoshinori.sato/qemu.git
>
> It include.
> - Minimal CPG support.
> - DT support
> - Add target LANDISK.

Thank you very much!
It would be a good idea to mention this is the cover letter of your
Linux patch series, so your test audience doesn't have to fix
already-solved problems...

BTW, your commit da64d6541226a516 ("hw/sh4: sh7750.c allow access
STBCR and STBCR2.") just ignores writes, and always returns zero
when reading.  This may cause issues with Linux code relying on
clock_ops.is_enabled() to return correct data.

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