Re: [PATCH v7 10/42] clk: davinci: New driver for davinci PSC clocks

[David Lechner]

On 03/01/2018 02:36 AM, Bartosz Golaszewski wrote:
> 2018-02-28 22:40 GMT+01:00 David Lechner <david@xxxxxxxxxxxxxx>:
> > On 02/28/2018 06:38 AM, Bartosz Golaszewski wrote:
> > > I think I found the reason for the strange crashes we were
> > > experiencing (emac core->name being NULL) thanks to Sekhar who pointed
> > > me in the right direction.
> > >
> > > The mdio driver fails to probe with v7 due to the supplied clock rate
> > > being wrong. Before failing we register the emac clock with
> > > pm_clk_add_clk(). When clock_ops puts the clock, it decreases the
> > > reference count of the clock, but we never actually increased it in
> > > the first place in the line above. The core clock code then destroys
> > > the associated clk_core structure. When the next user comes around (in
> > > our case the clk debug functions) the system crashes.
> > >
> > > I believe there to be two issues: one is with v7 - we need to increase
> > > the clock reference count in davinci_psc_genpd_attach_dev().
> > >
> > > Second is the error path in the clock framework - we should remove the
> > > destroyed clk_core from the debug list, which is not being done now.
> > >
> > > Why we even need to track the refcount of clk_core is a mistery for me
> > > though. Stephen, Mike?
> > >
> > > Best regards,
> > > Bartosz Golaszewski
> >
> >
> > Great find. I figured it had to be something like this, but I wasn't
> > able to reproduce the problem yet.
> >
> > I suppose it is time to spin up a v8 with some fixes.
>
> I still don't know why the mdio clock rate is much lower than in
> mainline though. Any ideas?
>
> Thanks,
> Bart

Now that you have fixed the crash, can you answer the questions I have
asked earlier?

> Can you post the output of this command so that I can see how your
clocks are setup:

cat /sys/kernel/debug/clk/clk_summary

> Using your workaround, can you run:

cat /sys/kernel/debug/pm_genpd/pm_genpd_summary

If you see:
  1e27000.clock-controller: emac  off-0

then genpd is not working like it is supposed to. You should see something
like this for device that are working:
          1e27000.clock-controller: uart2  on
    /devices/platform/soc@1c00000/1d0d000.serial        active