linux-kernel - Re: [PATCH v5 2/5] hwmon: (max31790) Fix and split pwm*

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Date:   Wed, 19 May 2021 11:10:10 +0200
From:   Jan Kundrát <jan.kundrat@...net.cz>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Václav Kubernát <kubernat@...net.cz>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>,
        <linux-hwmon@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/5] hwmon: (max31790) Fix and split pwm*_enable

> As it turns out, even the current code doesn't really work for fans 7..12.
> 		sr = get_tach_period(data->fan_dynamics[channel]);
> However, the data->fan_dynamics array has only 6 entries, not 12, so
> reading fan[7-12]_input will result in bad/random values.

Hi Guenter, I'm Vaclav's colleague. The chip can indeed reconfigure each 
PWMOUT pin either as a PWM output or as a TACH input, but that's not 
something that's correctly implemented in the current code, and we have no 
use for that either (and we cannot test that on our PCBs easily, we do not 
have the manufacturer's eval kit).

It looks to me that the original bug is that the current docs mention 12 
fan inputs. Would you be OK with a patch series which fixes the docs so 
that the chip always exports 6 TACH inputs and 6 PWMOUT channels?

Cheers,
Jan