[Letux-kernel] OMAP5: Debugging kernel not starting... (and clock: dpll_abe_ck failed transition to 'locked')

Tero Kristo t-kristo at ti.com
Wed Sep 12 19:19:45 CEST 2018


On 12/09/18 19:17, H. Nikolaus Schaller wrote:
> Hi Tony,
> 
>> Am 12.09.2018 um 02:03 schrieb Tony Lindgren <tony at atomide.com>:
>>
>> * H. Nikolaus Schaller <hns at goldelico.com> [180911 18:28]:
>>>> BTW: blacklisting pwm_bl makes CLKACTIVITY_DPLL_ABE_X2_CLK
>>>> show the right value but reboot still can't transition
>>>> dpll_abe_ck to 'locked'.
>>>
>>> After adding back all modules except pwm_omap_dmtimer the problem
>>> comes back to the Pyra. And adding a omap-dmtimer-pwm to the omap5-uevm.dts
>>> does make CLKACTIVITY_DPLL_ABE_X2_CLK become 0x803 as I see on the
>>> Pyra, but it still handles reboots properly.
>>>
>>> More test results to come tomorrow.
>>
>> OK good to hear you got it narrowed down.
> 
> I have further narrowed it down to
> 
> root at letux:~# more /etc/modprobe.d/pwm.conf
> blacklist pwm_omap_dmtimer
> blacklist snd_soc_omap_abe_twl6040
> root at letux:~#
> 
> which always reboots fine (tested with letux-4.18.7 and 4.19-rc1 and 4.14.58).
> 
> Either
> 
> 	modprobe pwm_omap_dmtimer
> 
> OR (!)
> 
> 	modprobe snd_soc_omap_abe_twl6040
> 
> before "reboot" makes the Pyra boot hang with the dpll_abe_ck failure.
> 
> Generally it reminds me a little of the pinctrl and generic-adc-battery
> drivers problem where it turned out that the main problem was a write-out-of-bounds
> in generic-adc-battery so that it did occur only if drivers were loaded in a
> specifc sequence.
> 
> But this here is more reproducible. On the Pyra.
> 
> I am still trying to reproduce the effect on the omap5evm by amending
> the mainline DTS. It does reboot with these modules loaded...
> 
> What I alread wonder is what
> 
> - dpll_abe_ck setup
> - pwm_omap_dmtimer
> - snd_soc_omap_abe_twl6040

They are most likely using the same source clock (dpll_abe_ck.)

- Some PWMs (GPtimers) use ABE as clock source, depending on DT config 
you might be using a PWM which uses ABE clocks
- Also TWL6040 uses ABE clock as source, as it is used for audio

-Tero

> 
> have in common so that they can influence each other?
> 
> hwmods? clock setup? dividers? plls?
> 
> BR,
> Nikolaus
> 

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