Re: [PATCH] mmc: sdhci-msm: Warn about overclocking SD/MMC

[Doug Anderson]

Hi,

On Thu, Dec 10, 2020 at 1:03 PM Stephen Boyd <swboyd@xxxxxxxxxxxx> wrote:
>
> Quoting Douglas Anderson (2020-12-10 12:57:25)
> > diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> > index 3451eb325513..dd41f6a4dbfb 100644
> > --- a/drivers/mmc/host/sdhci-msm.c
> > +++ b/drivers/mmc/host/sdhci-msm.c
> > @@ -353,6 +353,7 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> >         struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> >         struct mmc_ios curr_ios = host->mmc->ios;
> >         struct clk *core_clk = msm_host->bulk_clks[0].clk;
> > +       unsigned int achieved_rate;
>
> unsigned long?

I'm matching the type for the parameter.  ...but I guess you're right
that it's better to match clk_get_rate().

NOTE: I'm _not_ planning to change the parameter because it matches
the type in 'struct mmc_ios' and that feels like a much bigger change
to tweak.


> >         int rc;
> >
> >         clock = msm_get_clock_rate_for_bus_mode(host, clock);
> > @@ -363,6 +364,17 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> >                        curr_ios.timing);
> >                 return;
> >         }
> > +
> > +       /*
> > +        * Qualcomm clock drivers by default round clock _up_ if they can't
> > +        * make the requested rate.  This is not good for SD.  Yell if we
> > +        * encounter it.
> > +        */
> > +       achieved_rate = clk_get_rate(core_clk);
> > +       if (achieved_rate > clock)
> > +               pr_warn("%s: Card appears overclocked; req %u Hz, actual %d Hz\n",
>
> Can we use dev_warn?

What's here matches other prints including other ones in the same
function and in much of the MMC subsystem.  mmc_hostname() shows
"mmc1"

> dev_warn(mmc_dev(mmc)
> dev_warn(&msm_host->pdev->dev

This show "sdhci_msm 7c4000.sdhci"

I'm going to keep with tradition and keep using mmc_hostname().  In
some parts of this file they use both (a dev_warn that also includes
the mmc_hostname()) but that feels overkill.

> ?
>
> > +                       mmc_hostname(host->mmc), clock, achieved_rate);
> > +
> >         msm_host->clk_rate = clock;
> >         pr_debug("%s: Setting clock at rate %lu at timing %d\n",
> >                  mmc_hostname(host->mmc), clk_get_rate(core_clk),
>
> This could use achieved_rate now.

Sure.

I sent up a real quick v2 since it seemed like these were small fixes
and maybe this was all good otherwise.


-Doug