linux-kernel - Re: [PATCH 2/3] thermal: sun50i: add thermal driver for h6

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Date:   Mon, 13 May 2019 12:01:49 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Yangtao Li <tiny.windzz@...il.com>, rui.zhang@...el.com,
        edubezval@...il.com, daniel.lezcano@...aro.org, robh+dt@...nel.org,
        mark.rutland@....com, wens@...e.org, catalin.marinas@....com,
        will.deacon@....com, davem@...emloft.net,
        mchehab+samsung@...nel.org, gregkh@...uxfoundation.org,
        Jonathan.Cameron@...wei.com, nicolas.ferre@...rochip.com,
        paulmck@...ux.ibm.com, andy.gross@...aro.org, olof@...om.net,
        bjorn.andersson@...aro.org, jagan@...rulasolutions.com,
        marc.w.gonzalez@...e.fr, stefan.wahren@...e.com,
        enric.balletbo@...labora.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH 2/3] thermal: sun50i: add thermal driver for h6

On Mon, May 13, 2019 at 12:39:55AM +0200, Ondřej Jirman wrote:
> > +	/*
> > +	 * clkin = 24MHz
> > +	 * T acquire = clkin / (SUN50I_THS_CTRL0_T_ACQ + 1)
> > +	 *           = 20us
> > +	 */
> > +	regmap_write(tmdev->regmap, SUN50I_THS_CTRL0,
> > +		     SUN50I_THS_CTRL0_T_ACQ(479));
> > +	/* average over 4 samples */
> > +	regmap_write(tmdev->regmap, SUN50I_H6_THS_MFC,
> > +		     SUN50I_THS_FILTER_EN |
> > +		     SUN50I_THS_FILTER_TYPE(1));
> > +	/* period = (SUN50I_H6_THS_PC_TEMP_PERIOD + 1) * 4096 / clkin; ~10ms */
> > +	regmap_write(tmdev->regmap, SUN50I_H6_THS_PC,
> > +		     SUN50I_H6_THS_PC_TEMP_PERIOD(58));
>
> Also this math is not all that clear:
>
>   period = (SUN50I_H6_THS_PC_TEMP_PERIOD + 1) * 4096 / clkin; ~10ms
>
> SUN50I_H6_THS_PC_TEMP_PERIOD is a macro with an argument. So how does
> this work?
>
> Also, related to this, I've noticed that you removed the interrupt
> processing from the original driver. Without that you have to make sure
> that OF contains non-zero polling-delay and polling-delay-passive.
>
> Nonzero values are necessary for enabling polling mode of the tz core,
> otherwise tz core will not read values periodically from your driver.
>
> You should documment it in the DT bindings, too. Or keep the interrupt
> handling for THS.

If there's interrupts for this in the H6, yeah we should use them over
polling.

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com