linux-kernel - Re: [PATCH 1/2] configs: ARM: omap2plus: Enable OMAP3

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Date:   Tue, 22 Oct 2019 15:19:19 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Adam Ford <aford173@...il.com>
Cc:     Linux-OMAP <linux-omap@...r.kernel.org>,
        Adam Ford <adam.ford@...icpd.com>,
        "H. Nikolaus Schaller" <hns@...delico.com>,
        Benoît Cousson <bcousson@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] configs: ARM: omap2plus: Enable OMAP3_THERMAL

* Adam Ford <aford173@...il.com> [191022 19:01]:
> On Tue, Oct 22, 2019 at 11:22 AM Tony Lindgren <tony@...mide.com> wrote:
> >
> > Hi,
> >
> > * Adam Ford <aford173@...il.com> [191007 15:06]:
> > > The some in the OMAP3 family have a bandgap thermal sensor, but
> > > omap2plus has it disabled.
> > >
> > > This patch enables the OMAP3_THERMAL by default like the rest of
> > > the OMAP family.
> >
> > Looks like this breaks off mode during idle for omap3, and that's
> > probably why it never got enabled. The difference in power
> > consumption during idle is about 7mW vs 32mW for the SoC as
> > measured from torpedo shunt for main_battery_som.
> >
> > I think the right fix might be simply to add handling for
> > CPU_CLUSTER_PM_ENTER to the related thermal driver to disable
> > it during idle like we have for gpio-omap.c for example.
> 
> I am not sure I know where to start on fixing that issue.  Would you
> entertain enabling the driver if we set the device tree to 'disabled'
> by default?  This way if people want to to use it, it can be enabled
> on a per-device option.  Once the power stuff gets resolved, we might
> be able to enable it by default.  For people who are planning on using
> the DM3730 @ 1GHz in high temp environments, I am not sure they'll
> care about low power.

They should both work fine together though. They are not mutually
exclusive features.

> I'll try to look into it when I have time, but I was hoping a
> compromise might be a reasonable work-around.

It should be hopefully a trivial fix.. I have not looked at the
driver code though.

Regards,

Tony