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From: Guenter Roeck <linux@roeck-us.net>
To: Changhuang Liang <changhuang.liang@starfivetech.com>
Cc: Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-hwmon@vger.kernel.org" <linux-hwmon@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] hwmon: (starfive-fan-tach) Add fan tach driver for StarFive JHB100
Date: Thu, 20 Aug 2026 19:04:20 -0700	[thread overview]
Message-ID: <5bbbdc8d-828d-4b99-9581-c89cffb7c67a@roeck-us.net> (raw)
In-Reply-To: <ZQ4PR01MB1202A9B4F415BE121B6984B0F2A32@ZQ4PR01MB1202.CHNPR01.prod.partner.outlook.cn>

On 8/20/26 18:06, Changhuang Liang wrote:
...

>> So how long does it take to execute the "sensors" command with 16 active
>> fans ?
> 
> # time sensors
> starfive_fan_tach-isa-0000
> Adapter: ISA adapter
> fan1:           FAULT  (min =  300 RPM)
> fan2:           FAULT  (min =  300 RPM)
> fan3:           FAULT  (min =  300 RPM)
> fan4:           FAULT  (min =  300 RPM)
> fan5:           FAULT  (min =  300 RPM)
> fan6:           FAULT  (min =  300 RPM)
> fan7:           FAULT  (min =  300 RPM)
> fan8:           FAULT  (min =  300 RPM)
> fan9:           FAULT  (min =  300 RPM)
> fan10:          FAULT  (min =  300 RPM)
> fan11:          FAULT  (min =  300 RPM)
> fan12:          FAULT  (min =  300 RPM)
> fan13:          FAULT  (min =  300 RPM)
> fan14:          FAULT  (min =  300 RPM)
> fan15:          FAULT  (min =  300 RPM)
> fan16:       1800 RPM  (min =  300 RPM)
> 
> 
> real    0m4.865s
> user    0m0.023s
> sys     0m0.001s
> 

Normally I would say this is a no-go, but this is your chip
(and, as we say, your funeral). Just please document that reading
the fan status will take forever for disconnected fans.

Thanks,
Guenter


  parent reply	other threads:[~2026-08-21  2:04 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-19  9:15 [PATCH v2 0/2] Add JHB100 Fan-Tach support Changhuang Liang
2026-08-19  9:16 ` [PATCH v2 1/2] dt-bindings: hwmon: Add starfive,jhb100-fan-tach Changhuang Liang
2026-08-19  9:16 ` [PATCH v2 2/2] hwmon: (starfive-fan-tach) Add fan tach driver for StarFive JHB100 Changhuang Liang
2026-08-20  4:57   ` Guenter Roeck
2026-08-20  5:07     ` Guenter Roeck
2026-08-20 10:15     ` Changhuang Liang
2026-08-20 13:38       ` Guenter Roeck
2026-08-21  1:06         ` Changhuang Liang
2026-08-21  2:01           ` Guenter Roeck
2026-08-21  3:04             ` Changhuang Liang
2026-08-21  2:04           ` Guenter Roeck [this message]
2026-08-21  5:48             ` Changhuang Liang

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