Re: [PATCH v3 1/3] thermal: sun8i: add thermal driver for h6

From: Maxime Ripard <maxime.ripard@bootlin.com>
To: Frank Lee <tiny.windzz@gmail.com>
Cc: rui.zhang@intel.com, Eduardo Valentin <edubezval@gmail.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>, Chen-Yu Tsai <wens@csie.org>,
	David Miller <davem@davemloft.net>,
	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Nicolas Ferre <nicolas.ferre@microchip.com>,
	paulmck@linux.ibm.com, Linux PM <linux-pm@vger.kernel.org>,
	devicetree <devicetree@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 1/3] thermal: sun8i: add thermal driver for h6
Date: Fri, 14 Jun 2019 10:02:00 +0200	[thread overview]
Message-ID: <20190614080200.fc3mah5q3mmihxa5@flea> (raw)
In-Reply-To: <CAEExFWskAsNquULKBLtBFUOosNpks8L6aUhw-+cF=oZ0aghAtQ@mail.gmail.com>

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Hi,

On Thu, Jun 13, 2019 at 11:35:15PM +0800, Frank Lee wrote:
> On Thu, Jun 13, 2019 at 9:26 PM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> >
> > On Fri, Jun 07, 2019 at 09:34:44PM +0800, Frank Lee wrote:
> > > On Mon, May 27, 2019 at 8:27 PM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> > > > > +     ret = devm_request_threaded_irq(dev, irq, NULL,
> > > > > +                                     tmdev->chip->irq_thread,
> > > > > +                                     IRQF_ONESHOT, "ths", tmdev);
> > > > > +     if (ret)
> > > > > +             return ret;
> > > >
> > > > Is there any particular reason to use a threaded interrupt?
> > >
> > > Just to improve real-time.
> >
> > What do you mean by real-time here? If anything, that will increase
> > the latency of the interrupts here.
> >
> > And in preempt-rt, regular top-half interrupts will be forced into a
> > threaded interrupt anyway.
> >
> > > > > +static int sun8i_ths_remove(struct platform_device *pdev)
> > > > > +{
> > > > > +     struct ths_device *tmdev = platform_get_drvdata(pdev);
> > > > > +
> > > > > +     clk_disable_unprepare(tmdev->bus_clk);
> > > >
> > > > I know that we discussed that already, but I'm not sure why you switch
> > > > back to a regular call to regmap_init_mmio, while regmap_init_mmio_clk
> > > > will take care of enabling and disabling the bus clock for you?
> > >
> > > It seems that regmap_init_mmio_clk just get clk and prepare clk
> > > but no enable.
> >
> > At init time, yes. But it will enable it only when you access the
> > registers, which is what you want anyway.
>
> But after accessing the register, it turns the clock off, which
> affects the ad conversion and the occurrence of the interrupt.

Ah, so that's how it works. Yeah, it makes sense then.

> In addition, when resuming from suspend, we need to enable
> the clock, so I think it is necessary to have a clock pointer.

Yep, indeed.

Maxime

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

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