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From: Kevin Hilman <khilman@baylibre.com>
To: Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	Anand Moon <linux.amoon@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org,
	Neil Armstrong <narmstrong@baylibre.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
	linux-amlogic@lists.infradead.org, Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Jerome Brunet <jbrunet@baylibre.com>
Subject: Re: [RFCv1 5/5] arm64/ARM: configs: Change CONFIG_PWM_MESON from m to y
Date: Mon, 07 Oct 2019 15:57:59 -0700	[thread overview]
Message-ID: <7hsgo4cgeg.fsf@baylibre.com> (raw)
In-Reply-To: <CAFBinCAoJLZj9Kh+SfF4Q+0OCzac2+huon_BU=Q3yE7Fu38U3w@mail.gmail.com>

Martin Blumenstingl <martin.blumenstingl@googlemail.com> writes:

> On Mon, Oct 7, 2019 at 3:17 PM Anand Moon <linux.amoon@gmail.com> wrote:
> [...]
>> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
>> index c9a867ac32d4..72f6a7dca0d6 100644
>> --- a/arch/arm64/configs/defconfig
>> +++ b/arch/arm64/configs/defconfig
>> @@ -774,7 +774,7 @@ CONFIG_MPL3115=m
>>  CONFIG_PWM=y
>>  CONFIG_PWM_BCM2835=m
>>  CONFIG_PWM_CROS_EC=m
>> -CONFIG_PWM_MESON=m
>> +CONFIG_PWM_MESON=y
>
> some time ago I submitted a similar patch for the 32-bit SoCs
> it turned that that pwm-meson can be built as module because the
> kernel will run without CPU DVFS as long as the clock and regulator
> drivers are returning -EPROBE_DEFER (-517)

On 64-bit SoCs, the kernel boots with PWM as a module also, but DVFS
only works sometimes, and making it built-in fixes the problem.
Actually, it doesn't fix, it just hides the problem, which is likely a
race or timeout happening during deferred probing.

> did you check whether there's some other problem like some unused
> clock which is being disabled at that moment?
> I've been hunting weird problems in the past where it turned out that
> changing kernel config bits changed the boot timing - that masked the
> original problem

Right, I would definitely prefer to not make this built-in without a lot
more information to *why* this is needed.  In figuring that out, we'll
probably find the race/timeout that's the root cause.

Kevin



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  reply	other threads:[~2019-10-07 22:58 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-07 13:16 [RFCv1 0/5] Odroid N2 failes to boot using upstream kernel & u-boot Anand Moon
2019-10-07 13:16 ` [RFCv1 1/5] arm64: dts: meson: Add missing 5V_EN gpio signal for VCC5V regulator Anand Moon
2019-10-07 14:19   ` Neil Armstrong
2019-10-07 15:28     ` Anand Moon
2019-10-07 13:16 ` [RFCv1 2/5] arm64: dts: meson: Add missing pwm control gpio signal for pwm-regulator Anand Moon
2019-10-07 14:20   ` Neil Armstrong
2019-10-07 15:30     ` Anand Moon
2019-10-07 13:16 ` [RFCv1 3/5] arm64: dts: meson: Add missing regulator linked to VDDAO_3V3 regulator to FLASH_VDD Anand Moon
2019-10-07 14:20   ` Neil Armstrong
2019-10-07 15:53     ` Anand Moon
2019-10-07 13:16 ` [RFCv1 4/5] arm64: dts: meson: Add missing regulator linked to VCCV5 regulator to VDDIO_C/TF_IO Anand Moon
2019-10-07 14:21   ` Neil Armstrong
2019-10-07 15:54     ` Anand Moon
2019-10-07 13:16 ` [RFCv1 5/5] arm64/ARM: configs: Change CONFIG_PWM_MESON from m to y Anand Moon
2019-10-07 14:25   ` Neil Armstrong
2019-10-07 15:52     ` Anand Moon
2019-10-07 20:10   ` Martin Blumenstingl
2019-10-07 22:57     ` Kevin Hilman [this message]
2019-10-08 14:38       ` Anand Moon
2019-10-08 17:40         ` Martin Blumenstingl
2019-10-09  8:48           ` Anand Moon
2019-10-09 12:04             ` Jerome Brunet
2019-10-18 14:04               ` Anand Moon
2019-10-18 14:13                 ` Neil Armstrong
2019-10-18 15:21                   ` Anand Moon
2019-10-18 18:10                 ` Martin Blumenstingl
2019-10-21 14:11                   ` Anand Moon
2019-10-21 14:25                     ` Neil Armstrong
2019-10-21 15:41                       ` Anand Moon
2019-10-26 18:56                         ` Anand Moon
2019-10-24 20:20                     ` Martin Blumenstingl
2019-10-09 17:05             ` Martin Blumenstingl
2019-10-08  7:19     ` Anand Moon

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