Message-ID: <20190519142239.eolisexp5mrdyafz@core.my.home>
Date:   Sun, 19 May 2019 16:22:39 +0200
From:   Ondřej Jirman <megous@...ous.com>
To:     Frank Lee <tiny.windzz@...il.com>
Cc:     rui.zhang@...el.com, Eduardo Valentin <edubezval@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>, robh+dt@...nel.org,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>, catalin.marinas@....com,
        will.deacon@....com, David Miller <davem@...emloft.net>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan.Cameron@...wei.com,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        paulmck@...ux.ibm.com, Andy Gross <andy.gross@...aro.org>,
        olof@...om.net, bjorn.andersson@...aro.org,
        Jagan Teki <jagan@...rulasolutions.com>,
        marc.w.gonzalez@...e.fr, stefan.wahren@...e.com,
        enric.balletbo@...labora.com, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 2/3] thermal: sun50i: add thermal driver for h6

Hello Yangtao,

On Sat, May 18, 2019 at 12:34:57AM +0800, Frank Lee wrote:
> HI,
> 
> On Fri, May 17, 2019 at 2:29 AM Ondřej Jirman <megous@...ous.com> wrote:
> >
> > Hi Yangtao,
> >
> > thank you for work on this driver.
> >
> > On Fri, May 17, 2019 at 02:06:53AM +0800, Frank Lee wrote:
> > > HI Ondřej,
> > >
> > > On Mon, May 13, 2019 at 6:16 AM Ondřej Jirman <megous@...ous.com> wrote:
> > > > > +
> > > > > +/* Temp Unit: millidegree Celsius */
> > > > > +static int tsens_reg2temp(struct tsens_device *tmdev,
> > > > > +                           int reg)
> > > >
> > > > Please name all functions so that they are more clearly identifiable
> > > > in stack traces as belonging to this driver. For example:
> > > >
> > > >   sun8i_ths_reg2temp
> > > >
> > > > The same applies for all tsens_* functions below. tsens_* is too
> > > > generic.
> > >
> > > Done but no sun8i_ths_reg2temp.
> > >
> > > ths_reg2tem() should be a generic func.
> > > I think it should be suitable for all platforms， so no platform prefix.
> >
> > You've missed my point. The driver name is sun8i_thermal and if you get
> > and oops from the kernel you'll get a stack trace where there are just function
> > names. If you use too generic function names, it will not be clear which
> > driver is oopsing.
> >
> >   - sun8i_ths_reg2temp will tell you much more clearly where to search than
> >   - ths_reg2temp
> >
> > Of course you can always grep, but most thermal drivers are thermal sensor (ths)
> > drivers, and if multiple of them used this too-generic naming scheme you'd
> > have hard time debugging.
> >
> > Look at other thermal drivers. They usually encode driver name in the function
> > names to help with identification (even if these are static driver-local
> > functions).
> >
> 
> Can we change to sunxi_ths_ prefix?

It should probably match the driver name, but yes, that's better.

> > > > > +static int tsens_probe(struct platform_device *pdev)
> > > > > +{
> > > > > +     struct tsens_device *tmdev;
> > > > > +     struct device *dev = &pdev->dev;
> > > > > +     int ret;
> > > > > +
> > > > > +     tmdev = devm_kzalloc(dev, sizeof(*tmdev), GFP_KERNEL);
> > > > > +     if (!tmdev)
> > > > > +             return -ENOMEM;
> > > > > +
> > > > > +     tmdev->dev = dev;
> > > > > +     tmdev->chip = of_device_get_match_data(&pdev->dev);
> > > > > +     if (!tmdev->chip)
> > > > > +             return -EINVAL;
> > > > > +
> > > > > +     ret = tsens_init(tmdev);
> > > > > +     if (ret)
> > > > > +             return ret;
> > > > > +
> > > > > +     ret = tsens_register(tmdev);
> > > > > +     if (ret)
> > > > > +             return ret;
> > > >
> > > > Why split this out of probe into separate functions?
> > > >
> > > > > +     ret = tmdev->chip->enable(tmdev);
> > > > > +     if (ret)
> > > > > +             return ret;
> > > > > +
> > > > > +     platform_set_drvdata(pdev, tmdev);
> > > > > +
> > > > > +     return ret;
> > > > > +}
> > > > > +
> > > > > +static int tsens_remove(struct platform_device *pdev)
> > > > > +{
> > > > > +     struct tsens_device *tmdev = platform_get_drvdata(pdev);
> > > > > +
> > > > > +     tmdev->chip->disable(tmdev);
> > > > > +
> > > > > +     return 0;
> > > > > +}
> > > > > +
> > > > > +static int sun50i_thermal_enable(struct tsens_device *tmdev)
> > > > > +{
> > > > > +     int ret, val;
> > > > > +
> > > > > +     ret = reset_control_deassert(tmdev->reset);
> > > > > +     if (ret)
> > > > > +             return ret;
> > > > > +
> > > > > +     ret = clk_prepare_enable(tmdev->bus_clk);
> > > > > +     if (ret)
> > > > > +             goto assert_reset;
> > > > > +
> > > > > +     ret = tsens_calibrate(tmdev);
> > > > > +     if (ret)
> > > > > +             return ret;
> > > >
> > > > If this fails (it may likely fail with EPROBE_DEFER) you are leaving reset
> > > > deasserted, and clock enabled.
> > > >
> > > > Overall, I think, reset/clock management and nvmem reading will be common
> > > > to all the HW variants, so it doesn't make much sense splitting it out
> > > > of probe into separate functions, and makes it more error prone.
> > >
> > > Our long-term goal is to support all platforms.
> > > Bacicallt there is a differencr between each generation.
> > > So I feel it necessary to isolate these differences.
> > >
> > > Maybe:
> > > At some point, we can draw a part of the public part and platform
> > > difference into different
> > > files. something like qcom thermal driver.
> >
> > I understand, but I wrote ths drivers for H3/H5/A83T and it so far it looks like
> > all of them would share these 3 calls.
> >
> > You'll be enabling clock/reset and callibrating everywhere. So putting this to
> > per-SoC function seems premature.
> 
> In fact, enalbe and disable are the suspend and resume functions.(PM
> callback will be added in the future)
> When exiting from s2ram, the register will become the initial value.
> We need to do all the work, enabling reset/clk ,calibrating and
> initializing other reg.
> 
> So I think it is no need to put enabling reset/clk and calibrating to
> probe func, and I'd like
> to keep enable and disable func.

I know, I don't think it needs to be per-soc. These actions are all shared by
all SoCs. Maybe with an exception that some SoCs may need one more clock, but
that can be made optionally-required by some flag in struct sunxi_thermal_chip.

Only highly SoC specific thing is configuring the THS registers for sampling
frequency/averaging/enabling interrupts. The reset/clock enable is generic, and
already abstracted by the clock/reset framework.

So what I suggest is having:

sunxi_ths_enable()
	reset deassert
	bus clock prepare enable
	optionally module clock prepare enable (in the future)
	call per-soc calibration
	call per-soc setup callback

sunxi_ths_disable()
	reset assert
	bus clock unprepare disable
	optionally module clock unprepare disable

And if you could move devm_nvmem_cell_get to probe that should make per-SoC
calibration callback also less repetitive and could avoid undoing the enable
in case it returns EPROBE_DEFER (which is possible).

All this should make it easier to support PM in the future and add less
cumbersome to add support for A83T and H3/H5.

BTW, what are your plans for more SoC support? I'd like to add support for
A83T and H3/H5, maybe even during the 5.3 cycle if this driver happens to land
early enough. If you don't have any plans I'll take it on.

thank you and regards,
 	o.

> >
> > thank you and regards,
> >         o.
> >
> > > Regards,
> > > Yangtao
> 
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