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

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Date:   Tue, 1 Mar 2022 07:46:29 -0500
From:   Peter Geis <pgwipeout@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Heiko Stuebner <heiko@...ech.de>, linux-mmc@...r.kernel.org,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: host: dw-mmc-rockchip: avoid logspam when cd-broken

On Tue, Mar 1, 2022 at 7:38 AM Robin Murphy <robin.murphy@....com> wrote:
>
> On 2022-03-01 11:49, Peter Geis wrote:
> > On Tue, Mar 1, 2022 at 6:23 AM Robin Murphy <robin.murphy@....com> 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.

Alright, I'll look into this.
It seems only extremely low clock speeds fail and I know rockchip
chips have a hard time with extremely low clock rates.
I'll trace out where the failure is happening.

Thanks!

>
> 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@...il.com>
> >>> ---
> >>>    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) {