[PATCH 2/3] thermal: add support for the thermal sensor on Allwinner new SoCs

[Icenowy Zheng]

09.03.2017, 22:27, "Maxime Ripard" <maxime.ripard at free-electrons.com>:
> On Thu, Mar 09, 2017 at 08:36:24AM +0800, Icenowy Zheng wrote:
>>  02.03.2017, 22:11, "Maxime Ripard" <maxime.ripard at free-electrons.com>:
>>  > On Thu, Mar 02, 2017 at 12:02:13AM +0800, Icenowy Zheng wrote:
>>  >>  2017年3月1日 23:56于 Maxime Ripard <maxime.ripard at free-electrons.com>写道：
>>  >>  >
>>  >>  > On Wed, Mar 01, 2017 at 06:20:51PM +0800, Icenowy Zheng wrote:
>>  >>  > >
>>  >>  > > 2017年3月1日 18:14于 Maxime Ripard <maxime.ripard at free-electrons.com>写道：
>>  >>  > > >
>>  >>  > > > On Tue, Feb 28, 2017 at 03:18:13PM +0800, Icenowy Zheng wrote:
>>  >>  > > > >
>>  >>  > > > > 2017年2月28日 14:44于 Maxime Ripard <maxime.ripard at free-electrons.com>写道：
>>  >>  > > > > >
>>  >>  > > > > > On Tue, Feb 28, 2017 at 03:40:53AM +0800, Icenowy Zheng wrote:
>>  >>  > > > > > > From: Ondrej Jirman <megous at megous.com>
>>  >>  > > > > > >
>>  >>  > > > > > > Allwinner SoCs from H3 (including H5, A64, etc) have a new version of
>>  >>  > > > > > > thermal sensor, and needs a new driver for it.
>>  >>  > > > > > >
>>  >>  > > > > > > Add such a driver.
>>  >>  > > > > > >
>>  >>  > > > > > > Currently only H3 is supported, but other SoCs are easily to be
>>  >>  > > > > > > supported by adding new formula and set the sensor number.
>>  >>  > > > > > >
>>  >>  > > > > > > Signed-off-by: Ondřej Jirman <megous at megous.com>
>>  >>  > > > > > > [Icenowy: extend to support further multiple-sensor SoCs, change commit
>>  >>  > > > > > >  message]
>>  >>  > > > > > > Signed-off-by: Icenowy Zheng <icenowy at aosc.xyz>
>>  >>  > > > > >
>>  >>  > > > > > There's no need to create a new driver for that. This can be handled
>>  >>  > > > > > by the GPADC driver we already have.
>>  >>  > > > >
>>  >>  > > > > sun8i-ths is not GPADC at all.
>>  >>  > > > >
>>  >>  > > > > The latest SoC I know that use GPADC as thermal sensor is A33.
>>  >>  > > >
>>  >>  > > > It's not called the same way, but it definitely is an evolution of the
>>  >>  > > > same controller. There's no need for a new driver, only reworking what
>>  >>  > > > is already there.
>>  >>  > >
>>  >>  > > I don't think so -- here's some evidence:
>>  >>
>>  >>  But the H3 THS have many new IRQs, functions, different sampling
>>  >>  rate set method and a quite different register layout.
>>  >>
>>  >>  Doing this in GPADC driver is possible but meaningless.
>>  >>
>>  >>  > >
>>  >>  > > 1. The old GPADC do not have module clock.
>>  >>  >
>>  >>  > The A33 could use a PLL.
>>  >>
>>  >>  But it's a dedicated mod clk on new generation THS.
>>  >
>>  > And all of this really are evolutions. The block is still driven in
>>  > the exact same way. And this is where there is value in having the
>>  > same driver: you share the logic, which is mostly common, instead of
>>  > duplicating it.
>>
>>  After some thinking, I can accept a common driver for A23/A33 thermal
>>  sensor and H3/A64/H5 ones, but I cannot accept use iio-sun4i-gpadc
>>  driver for it, as now H3/A64/H5 thermal sensors are not just an ADC --
>>  they features hardware alarm levels, and in some SoC it become a
>>  multiple channel thermal sensor.
>
> The A23 and A33 is trivial to support on the already existing GPADC
> driver. If you have it already working on the A33, then the amount of
> work for your driver to support the A33, or for the GPADC to support
> the newer SoC is strictly the same.
>
> Except in one case, we have a common, debugged, already reviewed and
> already merged driver. In the other case, we have no such things.

I didn't see sun4i-gpadc iio driver in linux-next now, only the GPADC MFD.

And abstract a thermal-only ADC as a GPADC is not proper, especially when
it comes with some thermal-specific functions (hardware trip points).

So I do not accept it to be implemented as IIO ADC driver.

>
>>  I will insist on doing a dedicated driver for it, or if you like, I can add
>>  A23/A33 support to this driver. (Considering no one have already posted
>>  any patches for A23/A33 thermal sensor, except my old ones, so my
>>  work at least won't conflict with anything merged)
>
> http://lists.infradead.org/pipermail/linux-arm-kernel/2016-December/474821.html
>
> Maxime
>
> --
> Maxime Ripard, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com