linux-kernel - 回复: [DMARC error] [PATCH v3 3/3] arm64: dts: meson-s4-s905y4-khadas-vim1s: add initial device tree

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Message-ID:
 <PS1PPF62EEA9B1D287E26DFE619BB840508AE93A@PS1PPF62EEA9B1D.apcprd03.prod.outlook.com>
Date: Mon, 26 Jan 2026 09:35:04 +0000
From: Nick Xie <nick@...das.com>
To: George Stark <gnstark@...utedevices.com>
CC: "robh@...nel.org" <robh@...nel.org>, "khilman@...libre.com"
	<khilman@...libre.com>, "jbrunet@...libre.com" <jbrunet@...libre.com>,
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	"neil.armstrong@...aro.org" <neil.armstrong@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
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	"conor+dt@...nel.org" <conor+dt@...nel.org>, "kernel@...utedevices.com"
	<kernel@...utedevices.com>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "krzk+dt@...nel.org"
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	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nick@...qinick.com" <nick@...qinick.com>
Subject:
 回复: [DMARC error] [PATCH v3 3/3] arm64: dts: meson-s4-s905y4-khadas-vim1s: add initial device tree

> Thanks for the patch. Since you have khadas mail I'm pretty sure you've
> had the possibility to test it on the real vim board and I just don't
> get it how it works with the voltage table above. The problem is that
> pwm is calculated incorrectly in the upstream pwm-meson driver. That
> voltage table appeared to be used in early amlogic bl loader and
> appropriate pwm is initialized from a table's record. Duty cycle value
> is translated to pwm regs correctly. Later when kernel start running
> pwm-regulator driver is probed. It reads the pwm regs, calculates back
> duty-cyle and search it in the table. Since calculation algos are not
> match and the table doesn't contain full range of 0-100% values
> regulator driver doesn't find current voltage. In such case regulator
> core sets the minimum voltage from the table [1] and the SoC may hang
> (depending on board) due to minimum voltage may be too low for the
> current frequency SoC uses.

I'm not sure about the PWM issues, but I checked on the real S905Y4 hardware
and  it works.

> Or I'm missing something?


> There's not-yet-reviewed patch that fixes pwm algo [2]. There's
> calculation example in the cover letter.
> [1] https://elixir.bootlin.com/linux/v6.19-rc5/source/drivers/regulator/core.c#L1227
> [2] https://lkml.iu.edu/2412.3/00826.html

What's the status of such patches?

--

Best regards

George