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

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Message-ID: <CANAwSgRD-Vd-D1H5cDYMyTLRMfzdkrFuiy4KfXYt6S+0goF-2w@mail.gmail.com>
Date:   Mon, 21 Oct 2019 21:11:45 +0530
From:   Anand Moon <linux.amoon@...il.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Kevin Hilman <khilman@...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 Neil,

On Mon, 21 Oct 2019 at 19:55, Neil Armstrong <narmstrong@...libre.com> wrote:
>
> Hi Anand,
>
> On 21/10/2019 16:11, Anand Moon wrote:
> > 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.
>
> Thanks for the extensive debug.
>
> >
> > Attach is my local clk and dts patch.Just for testing.
> > [3] clk_critical.patch
>
>
> Could you test with only the following changes:
> diff --git a/drivers/clk/meson/g12a.c b/drivers/clk/meson/g12a.c
> index ea4c791f106d..f49f5463363e 100644
> --- a/drivers/clk/meson/g12a.c
> +++ b/drivers/clk/meson/g12a.c
> @@ -298,6 +298,7 @@ static struct clk_regmap g12a_fclk_div2 = {
>                         &g12a_fclk_div2_div.hw
>                 },
>                 .num_parents = 1,
> +               .flags = CLK_IS_CRITICAL,
>         },
>  };
>
> @@ -672,7 +673,7 @@ static struct clk_regmap g12b_cpub_clk = {
>                         &g12a_sys_pll.hw
>                 },
>                 .num_parents = 2,
> -               .flags = CLK_SET_RATE_PARENT,
> +               .flags = CLK_SET_RATE_PARENT | CLK_IS_CRITICAL,
>         },
>  };
>

Yes these changes work at my end,
I want to narrow down my changes, this looks pretty good.

Best Regards
-Anand