Re: [PATCH] mmc: host: dw-mmc-rockchip: avoid logspam when cd-broken

[Robin Murphy]

On 2022-03-01 11:49, Peter Geis wrote:
> On Tue, Mar 1, 2022 at 6:23 AM Robin Murphy <robin.murphy@xxxxxxx> wrote:
> > On 2022-02-28 22:36, Peter Geis wrote:
> > > The dw_mmc-rockchip driver drops a large amound of logspam constantly
> > > when the cd-broken flag is enabled.
> > > Set the warning to be debug ratelimited in this case.
> >
> > Isn't this just papering over some fundamental problem with the clock?
> > If it's failing to set the expected rate for communicating with a card,
> > then presumably that's an issue for correct operation in general? The
> > fact that polling for a card makes a lot more of that communication
> > happen seems unrelated :/
>
> Good Morning,
>
> This only happens when a card is not inserted, so communication cannot happen.

Well, I suppose there's a philosophical question in there about whether 
shouting into the void counts as "communication", but AFAIR what the 
polling function does is power up the controller, send a command, and 
see if it gets a response.

If the clock can't be set to the proper rate for low-speed discovery, 
some or all cards may not be detected properly. Conversely if it is 
already at a slow enough rate for discovery but can't be set higher once 
a proper communication mode has been established, data transfer 
performance will be terrible. Either way, it is not OK in general for 
clk_set_rate() to fail, hence the warning. You have a clock driver problem.

Cheers,
Robin.

> I found it while lighting off the SoQuartz module.
> As it is pin compatible with the RPi CM4, and the CM4 does not have a
> card detect line, sdmmc is non functional without cd-broken.
> This led to the fun spew when there wasn't a card inserted as this
> function is called every poll tick.
>
> Thanks,
> Peter
>
> > Robin.
> >
> > > Signed-off-by: Peter Geis <pgwipeout@xxxxxxxxx>
> > > ---
> > >    drivers/mmc/host/dw_mmc-rockchip.c | 9 +++++++--
> > >    1 file changed, 7 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/mmc/host/dw_mmc-rockchip.c b/drivers/mmc/host/dw_mmc-rockchip.c
> > > index 95d0ec0f5f3a..d0ebf0afa42a 100644
> > > --- a/drivers/mmc/host/dw_mmc-rockchip.c
> > > +++ b/drivers/mmc/host/dw_mmc-rockchip.c
> > > @@ -50,8 +50,13 @@ static void dw_mci_rk3288_set_ios(struct dw_mci *host, struct mmc_ios *ios)
> > >                cclkin = ios->clock * RK3288_CLKGEN_DIV;
> > >
> > >        ret = clk_set_rate(host->ciu_clk, cclkin);
> > > -     if (ret)
> > > -             dev_warn(host->dev, "failed to set rate %uHz\n", ios->clock);
> > > +     if (ret) {
> > > +             /* this screams when card detection is broken */
> > > +             if (host->slot->mmc->caps & MMC_CAP_NEEDS_POLL)
> > > +                     dev_dbg_ratelimited(host->dev, "failed to set rate %uHz\n", ios->clock);
> > > +             else
> > > +                     dev_warn(host->dev, "failed to set rate %uHz\n", ios->clock);
> > > +     }
> > >
> > >        bus_hz = clk_get_rate(host->ciu_clk) / RK3288_CLKGEN_DIV;
> > >        if (bus_hz != host->bus_hz) {