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

[David Lechner]

On 03/05/2018 10:23 AM, David Lechner wrote:
> On 03/05/2018 07:02 AM, Bartosz Golaszewski wrote:
> > 2018-03-01 17:44 GMT+01:00 David Lechner <david@xxxxxxxxxxxxxx>:
> > > 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:
> > > ÂÂÂÂÂÂÂÂÂÂ 1e27000.clock-controller: uart2Â on
> > > ÂÂÂÂ /devices/platform/soc@1c00000/1d0d000.serialÂÂÂÂÂÂÂ active
> >
> > Hi David, Sekhar,
> >
> > I tried booting the board today over tftp but didn't succeed. I then
> > switched to a normal boot from SD card and the boot process froze at
> > the same moment (right after the DHCP config, or after rtc config if I
> > disabled DHCP in bootargs). I then realized that the emac clock can't
> > be the culprit. After some digging I found out that the late_initcall
> > to clk_disable_unused() disables sysclk6 - the parent of the arm
> > clock, which of course freezes the device.
> >
> > If I remove the call to clk_disable_unused(), I can boot just fine.
> >
> > The following other clocks are disabled before pll0_sysclk6:
> > pll1_sysclk3
> > pll0_obsclk
> > pll0_sysclk7
> >
> > davinci_lpsc_clk_enable() is never called for these clocks - in fact
> > it's not called for any parent that's not explicitly defined in
> > psc-da850.c - I believe this may be one of the reasons. I will get
> > back to debugging it tomorrow.
> >
> > Best regards,
> > Bartosz Golaszewski
>
> Thanks for continuing to dig into this. I think I know what needs to
> be done now. I think I don't have the dependencies quite right where
> the PSC clocks are being registered before the PLL clocks, in which
> case they aren't getting the correct parent clock.

Bartosz,

One more thing to check: I think I had some typos in da850.dtsi where
I wrote clock_names instead of clock-names. Please make sure this is
fixed in your working branch.