Message-ID: <CANAwSgRs2DUXwvhJD5qpXg04qEdP_Nt-wQqRbD2FpY2SWnHpAA@mail.gmail.com>
Date:   Mon, 21 Oct 2019 19:41:34 +0530
From:   Anand Moon <linux.amoon@...il.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        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

Hi Martin,

On Fri, 18 Oct 2019 at 23:40, Martin Blumenstingl
<martin.blumenstingl@...glemail.com> wrote:
>
> Hi Anand,
>
> On Fri, Oct 18, 2019 at 4:04 PM Anand Moon <linux.amoon@...il.com> wrote:
> [...]
> > > 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.
> > >
> >
> > I had give this above steps a try but with little success.
> > I am still looking into this much close.
> it's not clear to me if you have only tested with the PWM and/or
> FCLK_DIV4 clocks. can you please describe what you have tested so far?
>
Sorry for delayed response.

I had just looked into clk related to SD_EMMC_A/B/C,
with adding CLK_IGNORE/CRITICAL.
Also looked into clk_summary for eMMC and microSD card,
to identify the root cause, but I failed to move ahead.

> for reference - my way of debugging this in the past was:
> 1. add some printks to clk_disable_unused_subtree (right after the
> clk_core_is_enabled check) to see which clocks are being disabled
> 2. add CLK_IGNORE_UNUSED or CLK_IS_CRITICAL to the clocks which are
> being disabled based on the information from step #1
> 3. (at some point I had a working kernel with lots of clocks with
> CLK_IGNORE_UNUSED/CLK_IS_CRITICAL)
> 4. start dropping the CLK_IGNORE_UNUSED/CLK_IS_CRITICAL flags again
> until you have traced it down to the clocks that are the actual issue
> (so far I always had only one clock which caused issues, but it may be
> multiple)
> 5. investigate (and/or ask on the mailing list, Amlogic developers are
> reading the mails here as well) for the few clocks from step #4
>

Thanks for you valuable suggestion. I have your patch to debug this
[0]  https://patchwork.kernel.org/patch/9725921/mbox/

So from the fist step I could identify that all the clk were getting closed
after some core cpu clk was failing. Here is the log.

step1: [1] https://pastebin.com/p13F9HGG

so I marked these clk as CLK_IGNORE_UNUSED and finally
I made it to boot using microSD card.

After this just I converted these CLK to CLK_IS_CRITICAL
as mostly these are used the CPU clk for now.
Here is boot log successful for as of now.

Finally: [2]  https://pastebin.com/qB6pMyGQ

I know clk maintainer are against marking flags as *CLK_IS_CRITICAL*
But this is just the step to move ahead.

Attach is my local clk and dts patch.Just for testing.
[3] clk_critical.patch

Plz share your thought on this.

> > Well I am not the expert in clk or bus configuration.
> > but after looking into the datasheet of for clk configuration
> > I found some bus are not configured correctly.
> did you find any reason which indicates that the problem is related to a bus?
> the issues I had were due to clocks not being assigned to their
> consumers in .dts - that can be anything (from a bus to something
> different).
>

Yes I feel each core bus should be independent
as each clk PLL controls these bus.

for example datasheet: *6-5 Clock Connections*

What I feel currently missing with bus are
clock gating (enable/disable of features).
clock-controller
reset-controller

Here is the current overview of bus topology
using latest u-boot (dm tree).

[4] https://pastebin.com/MZ25bgiP

Bet Regards
-Anand

Download attachment "clk_critical.patch" of type "application/octet-stream" (5614 bytes)

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