From: "Uwe Kleine-König" <ukleinek@kernel.org>
To: Xuyang Dong <dongxuyang@eswincomputing.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>,
robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org,
ben-linux@fluff.org, ben.dooks@codethink.co.uk,
p.zabel@pengutronix.de, linux-pwm@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
ningyu@eswincomputing.com, linmin@eswincomputing.com,
xuxiang@eswincomputing.com, wangguosheng@eswincomputing.com,
pinkesh.vaghela@einfochips.com
Subject: Re: [PATCH v2 1/2] dt-bindings: pwm: dwc: add reset optional
Date: Tue, 17 Mar 2026 10:42:38 +0100 [thread overview]
Message-ID: <abkg_5PlNLfyAEmw@monoceros> (raw)
In-Reply-To: <2d4f2cf9.3fe0.19cd1e8df20.Coremail.dongxuyang@eswincomputing.com>
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Hello,
On Mon, Mar 09, 2026 at 05:23:45PM +0800, Xuyang Dong wrote:
> The DesignWare PWM controller provides separate reset signals dedicated
> to each clock domain, as specified in the hardware documentation.
> Without asserting and deasserting these resets during probe, the PWM
> output may remain in an undefined state after system reboot.
Note there is an additional difficulty: A usual wish for machines with a
display is that the bootloader sets up a splash screen that is smoothly
taken over by Linux during boot. A reset of the PWM driving the
backlight then most probably results in a short dark display which
doesn't qualify for smooth.
So if you have a way to distinguish between "random state after
power-on" and "already programmed by the bootloader" this would be
great.
Best regards
Uwe
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next prev parent reply other threads:[~2026-03-17 9:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-06 9:30 [PATCH v2 0/2] Update designware pwm driver dongxuyang
2026-03-06 9:30 ` [PATCH v2 1/2] dt-bindings: pwm: dwc: add reset optional dongxuyang
2026-03-07 13:22 ` Krzysztof Kozlowski
2026-03-09 9:23 ` Xuyang Dong
2026-03-17 9:42 ` Uwe Kleine-König [this message]
2026-03-06 9:31 ` [PATCH v2 2/2] pwm: dwc: add of/platform support dongxuyang
2026-03-07 13:24 ` [PATCH v2 0/2] Update designware pwm driver Krzysztof Kozlowski
2026-03-07 13:26 ` Krzysztof Kozlowski
2026-03-09 9:24 ` Xuyang Dong
2026-03-17 13:50 ` Ben Dooks
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