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Date:   Sat, 9 Nov 2019 04:02:00 -0600
From:   Adam Ford <aford173@...il.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, linux-pm@...r.kernel.org,
        Tony Lindgren <tony@...mide.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Enric Balletbo i Serra <eballetbo@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        André Roth <neolynx@...il.com>,
        Benoît Cousson <bcousson@...libre.com>,
        kernel@...a-handheld.com, Teresa Remmet <t.remmet@...tec.de>,
        Javier Martinez Canillas <javier@...hile0.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        Roger Quadros <rogerq@...com>
Subject: Re: [PATCH v3 0/8] OMAP3: convert opp-v1 to opp-v2 and read speed
 binned / 720MHz grade bits

On Sat, Nov 9, 2019 at 12:12 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
>
> Hi Adam,
>
> > Am 08.11.2019 um 21:08 schrieb Adam Ford <aford173@...il.com>:
> >
> >
> > Nikolaus,
> >
> > I am getting some notices sent to me when I apply your series.  It
> > works, but I want to clean up the notice.  Can you suggest what might
> > cause this:
> >
> >     debugfs: Directory 'cpu0-cpu0' with parent
> > '48070000.i2c:twl@48:regulator-vdd1-VDD1' already present!
> >
> > It wasn't present before your series.  It's not a big deal, but I'd
> > like to quiet down the messages if I can.
> > Thanks.
>
> I have checked and can also see this message - and it should be removed.
>
> There is a debugfs node at:
>
> /sys/kernel/debug/regulator/48070000.i2c:twl@48:regulator-vdd1-VDD1/cpu0-cpu0
>
> OMAP5 also has a similar node but no such debugfs warning:
>
> /sys/kernel/debug/regulator/smps123/cpu0-cpu0
>
> So what I suspect is some bug in the twl4030 regulator driver which is
> just revealed by my patch series for the first time.

I was wondering that too.

>
> Could it be that the debugfs node is created and not cleaned up by deferred
> probing?

That would make sense to me.

>
> But this is not explicitly done in drivers/regulator/twl-regulator.c
>
> BTW: twl6030 and palmas (twl6037) have separate driver, so that mentioning
> twl6030 in the comments in drivers/regulator/twl-regulator.c may be wrong.
> It also mentions some "TW5030" which I have never heard of.
>
> To find out the call sequence I added a dump_stack to start_creating()
> after the error message is printed:
>
>
> [    2.289947] debugfs: Directory 'cpu0-cpu0' with parent '48070000.i2c:twl@48:regulator-vdd1-VDD1' already present!
> [    2.301727] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc6-letux+ #1329
> [    2.309112] Hardware name: Generic OMAP36xx (Flattened Device Tree)
> [    2.315734] [<c0110028>] (unwind_backtrace) from [<c010b60c>] (show_stack+0x10/0x14)
> [    2.323852] [<c010b60c>] (show_stack) from [<c07b9b60>] (dump_stack+0x7c/0x9c)
> [    2.331420] [<c07b9b60>] (dump_stack) from [<c0373588>] (start_creating+0xa8/0x104)
> [    2.339477] [<c0373588>] (start_creating) from [<c0373fb0>] (debugfs_create_dir+0xc/0xc0)
> [    2.348052] [<c0373fb0>] (debugfs_create_dir) from [<c04e96e0>] (create_regulator+0xd0/0x1c8)
> [    2.356994] [<c04e96e0>] (create_regulator) from [<c04ec608>] (_regulator_get+0x190/0x224)
> [    2.365661] [<c04ec608>] (_regulator_get) from [<c06653d0>] (dt_cpufreq_probe+0x80/0x108)
> [    2.374237] [<c06653d0>] (dt_cpufreq_probe) from [<c053e018>] (platform_drv_probe+0x48/0x98)
> [    2.383087] [<c053e018>] (platform_drv_probe) from [<c053c3a8>] (really_probe+0x164/0x324)
> [    2.391754] [<c053c3a8>] (really_probe) from [<c053c7b8>] (driver_probe_device+0x10c/0x154)
> [    2.400512] [<c053c7b8>] (driver_probe_device) from [<c053a9f4>] (bus_for_each_drv+0x90/0xb8)
> [    2.409423] [<c053a9f4>] (bus_for_each_drv) from [<c053c5f8>] (__device_attach+0x90/0x120)
> [    2.418090] [<c053c5f8>] (__device_attach) from [<c053b628>] (bus_probe_device+0x28/0x80)
> [    2.426666] [<c053b628>] (bus_probe_device) from [<c05393ec>] (device_add+0x2f0/0x55c)
> [    2.434967] [<c05393ec>] (device_add) from [<c053decc>] (platform_device_add+0x12c/0x1b8)
> [    2.443542] [<c053decc>] (platform_device_add) from [<c053e954>] (platform_device_register_full+0xec/0x13c)
> [    2.453765] [<c053e954>] (platform_device_register_full) from [<c0665ff4>] (ti_cpufreq_probe+0x298/0x2fc)
> [    2.463775] [<c0665ff4>] (ti_cpufreq_probe) from [<c053e018>] (platform_drv_probe+0x48/0x98)
> [    2.472625] [<c053e018>] (platform_drv_probe) from [<c053c3a8>] (really_probe+0x164/0x324)
> [    2.481292] [<c053c3a8>] (really_probe) from [<c053c7b8>] (driver_probe_device+0x10c/0x154)
> [    2.490051] [<c053c7b8>] (driver_probe_device) from [<c053a9f4>] (bus_for_each_drv+0x90/0xb8)
> [    2.498992] [<c053a9f4>] (bus_for_each_drv) from [<c053c5f8>] (__device_attach+0x90/0x120)
> [    2.507629] [<c053c5f8>] (__device_attach) from [<c053b628>] (bus_probe_device+0x28/0x80)
> [    2.516204] [<c053b628>] (bus_probe_device) from [<c05393ec>] (device_add+0x2f0/0x55c)
> [    2.524505] [<c05393ec>] (device_add) from [<c053decc>] (platform_device_add+0x12c/0x1b8)
> [    2.533081] [<c053decc>] (platform_device_add) from [<c053e954>] (platform_device_register_full+0xec/0x13c)
> [    2.543304] [<c053e954>] (platform_device_register_full) from [<c0665d2c>] (ti_cpufreq_init+0x78/0xa8)
> [    2.553039] [<c0665d2c>] (ti_cpufreq_init) from [<c0102ed8>] (do_one_initcall+0xb4/0x268)
> [    2.561645] [<c0102ed8>] (do_one_initcall) from [<c0b00fe4>] (kernel_init_freeable+0x11c/0x1ec)
> [    2.570770] [<c0b00fe4>] (kernel_init_freeable) from [<c07cf1c8>] (kernel_init+0x8/0x110)
> [    2.579345] [<c07cf1c8>] (kernel_init) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
> [    2.587249] Exception stack(0xde0b1fb0 to 0xde0b1ff8)
> [    2.592559] 1fa0:                                     00000000 00000000 00000000 00000000
> [    2.601135] 1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [    2.609680] 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000
>
>
> So the problem seems to be that ti_cpufreq_probe() tries to register the regulators
> "vdd" and "vbb" without properly checking if they have been registered elsewhere.
>
> The second attempt to create the debugfs directory seems to come from resources_available()
> which thinks that it has to create the regulator (again) [around line 1935 in drivers/regulator/core.c].
>
> Hope this helps, although I have no idea why the vdd regulator already exists at that point.

Thank you for the detailed analysis.


>
> BR,
> Nikolaus
>
>
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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