linux-kernel - Re: [PATCH 3/3] ACPI / PMIC: Add opregion driver for Intel Dollar Cove TI PMIC

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Date:   Tue, 22 Aug 2017 14:06:26 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Johannes Stezenbach <js@...21.net>,
        linux-input@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 3/3] ACPI / PMIC: Add opregion driver for Intel Dollar Cove TI PMIC

On Tue, 22 Aug 2017 13:37:21 +0200,
Andy Shevchenko wrote:
> 
> On Tue, 2017-08-22 at 13:01 +0200, Takashi Iwai wrote:
> > On Tue, 22 Aug 2017 12:25:12 +0200,
> > Takashi Iwai wrote:
> > > 
> > > On Tue, 22 Aug 2017 11:58:35 +0200,
> > > Andy Shevchenko wrote:
> > > > 
> > > > On Tue, 2017-08-22 at 07:57 +0200, Takashi Iwai wrote:
> > > > > This patch adds the opregion driver for Dollar Cove TI PMIC on
> > > > > Intel
> > > > > Cherry Trail devices.  The patch is based on the original work
> > > > > by
> > > > > Intel, found at:
> > > > >       https://github.com/01org/ProductionKernelQuilts
> > > > > with many cleanups and rewrites.
> > > > > 
> > > > > The driver is currently provided only as built-in to follow
> > > > > other
> > > > > PMIC opregion drivers convention.
> > > > > 
> > > > > The re-enumeration of devices at probe is required for fixing
> > > > > the
> > > > > issues on HP x2 210 G2.  See bug#195689.
> > > > > 
> > > > > 
> > > > > +static int dc_ti_pmic_get_raw_temp(struct regmap *regmap, int
> > > > > reg)
> > > > > +{
> > > > > +	int temp_l, temp_h;
> > > > > +
> > > > > +	if (regmap_read(regmap, reg, &temp_l) ||
> > > > > +	    regmap_read(regmap, reg - 1, &temp_h))
> > > > > +		return -EIO;
> > > > > +
> > > > > +	return temp_l | (temp_h & 0x3) << 8;
> > > > > +}
> > > > 
> > > > I'm not sure I understand this "- 1" part along with choice of l
> > > > and h
> > > > suffixes.
> > > > 
> > > > Does it mean the register is big endian?
> > > 
> > > Good point, I need to check the original code and the values.
> > 
> > It's really big-endian, the order is hi:lo.
> > 
> > But, admittedly, the temperature code hasn't been tested, and it's
> > possibly missing something.  So I'm fine to drop that part in the
> > first version, too.
> 
> I don't know if regmap allows you to define registers with different
> sizes for same chip, perhaps it would make sense to start register from
> hi part (and not doing non-intuitive "- 1", or maybe "+ 1" instead) and
> mark it in comment that is BE16.

I don't think regmap would allow different bit size, so combining
still needed.  But yeah, it's better to start from the high register
with the lower address and use +1.


thanks,

Takashi