linux-kernel - Re: [PATCH v5 2/2] mmc: Add mmc driver for Sunplus SP7021

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Date:   Thu, 31 Mar 2022 12:17:26 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Tony Huang 黃懷厚 <tony.huang@...plus.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Tony Huang <tonyhuang.sunplus@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        "lhjeff911@...il.com" <lhjeff911@...il.com>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Wells Lu 呂芳騰 <wells.lu@...plus.com>,
        Lh Kuo 郭力豪 <lh.Kuo@...plus.com>
Subject: Re: [PATCH v5 2/2] mmc: Add mmc driver for Sunplus SP7021

On Thu, Mar 31, 2022 at 11:27 AM Tony Huang 黃懷厚 <tony.huang@...plus.com> wrote:
> > > +static void spmmc_request(struct mmc_host *mmc, struct mmc_request
> > > +*mrq) {
> > > +       struct spmmc_host *host = mmc_priv(mmc);
> > > +       struct mmc_data *data;
> > > +       struct mmc_command *cmd;
> > > +       int ret;
> > > +
> > > +       ret = mutex_lock_interruptible(&host->mrq_lock);
> > > +       if (ret)
> > > +               return;
> >
> > I don't think it's valid to just return here when you get a signal. If nothing can
> > handle the signal, doesn't it just hang?
> >
> > It also appears that you don't release the mutex until the tasklet runs, but it is
> > not valid to release a mutex from a different context.
> >
> > You should get a warning about this when running a kernel with lockdep
> > enabled at compile time. Please rework the locking to make this work.
> >
>         Reomve code:
>     ret = mutex_lock_interruptible(&host->mrq_lock);
>     if (ret)
>          return;
>
>         Below is my modification:
> .    mutex_lock(&host->mrq_lock);

That addresses the problem with the signal handling, but not the lock
imbalance. Please fix that as well.
> >
> > It's better to use SYSTEM_SLEEP_PM_OPS/RUNTIME_PM_OPS instead of the
> > SET_ version, then you can remove all the #ifdef checks.
> >
>
>         I use SYSTEM_SLEEP_PM_OPS/RUNTIME_PM_OPS.
>         Compile shows error. Error: implicit declaration of function ? ? SYSTEM_SLEEP_PM_OPS? ? Did you mean ? ? SET_SYSTEM_SLEEP_PM_OPS? ?             [-Werror=implicit-function-declaration]

Maybe you are on an old kernel release?

>         I reference other mmc driver.
>         Below is my modification:
>     Compiler is pass.
>
>         #ifdef CONFIG_PM_SLEEP
>         static int spmmc_pm_suspend(struct device *dev)
>         {
>                 pm_runtime_force_suspend(dev);
>
>                 return 0;
>         }

We should fix the other drivers as well. For the moment, just do it
the right way now
instead of copying the #ifdefs.

        Arnd