linux-kernel - Re: [v2 3/3] hwmon: Add Aspeed ast2600 TACH support

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Date:   Wed, 2 Nov 2022 21:30:34 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Billy Tsai <billy_tsai@...eedtech.com>
Cc:     "jdelvare@...e.com" <jdelvare@...e.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "joel@....id.au" <joel@....id.au>,
        "andrew@...id.au" <andrew@...id.au>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        BMC-SW <BMC-SW@...eedtech.com>,
        "garnermic@...a.com" <garnermic@...a.com>
Subject: Re: [v2 3/3] hwmon: Add Aspeed ast2600 TACH support

On Thu, Nov 03, 2022 at 03:52:59AM +0000, Billy Tsai wrote:
> 
> Can't I use a min/max RPM to let the driver know a reasonable timeout/polling period when
> the driver is trying to get RPM?
> Beacause that our tach controller have the falg to indicates the hardware detected the change
> in the input signal. I need the proper timout to rule out slow RPMs.
> 

If the chip measures the fan speed continuously, why would that ever be a
problem, and why wait in the first place instead of just taking the most
recent result ?

Pretty much every other driver is doing that, so I really don't understand
why that would not work here.

Guenter