linux-kernel - Re: [RFCv1 5/5] arm64/ARM: configs: Change CONFIG_PWM

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Date:   Wed, 09 Oct 2019 14:04:41 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Anand Moon <linux.amoon@...il.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-amlogic@...ts.infradead.org,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFCv1 5/5] arm64/ARM: configs: Change CONFIG_PWM_MESON from m to y


On Wed 09 Oct 2019 at 10:48, Anand Moon <linux.amoon@...il.com> wrote:
>
> Kernel command line: console=ttyAML0,115200n8
> root=PARTUUID=45d7d61e-01 rw rootwait
> earlyprintk=serial,ttyAML0,115200 initcall_debug printk.time=y
>
> [0] https://pastebin.com/eBgJrSKe
>
>> you can also try the command line parameter "clk_ignore_unused" (it's
>> just a gut feeling: maybe a "critical" clock is being disabled because
>> it's not wired up correctly).
>>
>
> It look like some clk issue after I added the *clk_ignore_unused* to
> kernel command line
> it booted further to login prompt and cpufreq DVFS seem to be loaded.
> So I could conclude this is clk issue.below is the boot log
>
> Kernel command line: console=ttyAML0,115200n8
> root=PARTUUID=45d7d61e-01 rw rootwait
> earlyprintk=serial,ttyAML0,115200 initcall_debug printk.time=y
> clk_ignore_unused
>
> [1] https://pastebin.com/Nsk0wZQJ
>

Next step it to try narrow down the clock causing the issue.
Remove clk_ignore_unused from the command line and add CLK_INGORE_UNUSED
to the flag of some clocks your clock controller (g12a I think) until

The peripheral clock gates already have this flag (something we should
fix someday) so don't bother looking there.

Most likely the source of the pwm is getting disabled between the
late_init call and the probe of the PWM module. Since the pwm is already
active (w/o a driver), gating the clock source shuts dowm the power to
the cores.

Looking a the possible inputs in pwm driver, I'd bet on fdiv4.