Re: [PATCH v2] mmc: sdhi: fill in actual_clock

[TamÃs SzÅcs]

Hi Geert,

You are correct, there is no way to distinguish between the old and new kernels just by mmc ios output when the bus is down. I don't think it's an issue. I find it more helpful to have this information available.
Yes, actual_clock should only display when non-zero and it should be zero when the bus is down. I fixed this in v2.

Kind regards,
Tamas


TamÃs SzÅcs
tszucs@xxxxxxxxxxxxx

âââââââ Original Message âââââââ
On Friday, August 30, 2019 9:21 AM, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:

> Hi TamÃs,
>
> On Thu, Aug 29, 2019 at 8:37 PM TamÃs SzÅcs tszucs@xxxxxxxxxxxxx wrote:
>
> > Save set clock in mmc_host actual_clock enabling exporting it via debugfs.
> > This will indicate the precise SD clock in I/O settings rather than only the
> > sometimes misleading requested clock.
> > Signed-off-by: TamÃs SzÅcs tszucs@xxxxxxxxxxxxx
>
> Thanks for the update!
>
> Reviewed-by: Geert Uytterhoeven geert+renesas@xxxxxxxxx
>
> However, one question below.
>
> > --- a/drivers/mmc/host/renesas_sdhi_core.c
> > +++ b/drivers/mmc/host/renesas_sdhi_core.c
> > @@ -166,10 +166,13 @@ static void renesas_sdhi_set_clock(struct tmio_mmc_host *host,
> > sd_ctrl_write16(host, CTL_SD_CARD_CLK_CTL, ~CLK_CTL_SCLKEN &
> > sd_ctrl_read16(host, CTL_SD_CARD_CLK_CTL));
> >
> > -         if (new_clock == 0)
> >
> >
> >
> > -         if (new_clock == 0) {
> >
> >
> > -                 host->mmc->actual_clock = 0;
> >
> >
>
> The actual clock is present in the debugfs output only when non-zero.
> Hence userspace cannot distinguish between an old kernel where the
> Renesas SDHI driver didn't fill in actual_clock, and a new kernel when
> the SDHI controller is powered down.
> Could that be an issue? Should the old value be retained?
> Probably it's OK, as this is debugfs, not an official ABI.
>
> 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