linux-kernel - Re: [PATCH v1] hwmon: (lm90) Use edge-triggered interrupt

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Message-ID: <20210617214257.GD2244035@roeck-us.net>
Date:   Thu, 17 Jun 2021 14:42:57 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v1] hwmon: (lm90) Use edge-triggered interrupt

On Thu, Jun 17, 2021 at 06:27:50PM +0300, Dmitry Osipenko wrote:
> 17.06.2021 18:12, Guenter Roeck пишет:
> >> For now I see that the rising edge isn't needed, the TEMP_ALERT goes
> >> HIGH by itself when temperature backs to normal. But I will try to
> >> double check.
> >>
> > The point is that a sysfs event should be sent to userspace on both
> > edges, not only when an alarm is raised. But, you are correct,
> > IRQ_TYPE_EDGE_RISING is currently not needed since sysfs events
> > are not generated.
> 
> Ok, thank you for the clarification.
> 
> >>> Anyway, the tegra30 dts files in the upstream kernel either use
> >>> IRQ_TYPE_LEVEL_LOW or no interrupts for nct1008. The Nexus 7 dts file
> >>> in the upstream kernel has no interrupt configured (and coincidentally
> >>> it was you who added that entry). Where do you see IRQ_TYPE_LEVEL_HIGH ?
> >> I have a patch that will add the interrupt property, it's stashed
> >> locally for the next kernel release.
> >>
> >> IIUC, it's not only the Tegra30 dts, but all the TegraXXX boards that
> >> use IRQ_TYPE_LEVEL_LOW are in the same position.
> > I still don't see a IRQ_TYPE_LEVEL_HIGH, though.
> 
> Could you please clarify why you're looking for HIGH and not for LOW?
> The TEMP_ALERT is active-low.

Because you stated earlier:

"... cargo-culted and wrong because they use IRQ_TYPE_LEVEL_HIGH ..."
                                             ^^^^^^^^^^^^^^^^^^^

Guenter