Re: [PATCH v2 2/2] reset: Reset controller driver for Intel LGM SoC

[Dilip Kota]

Hi Martin,Philipp,

On 10/8/2019 3:53 AM, Martin Blumenstingl wrote:
> Hi Philipp,
>
> On Thu, Oct 3, 2019 at 4:19 PM Philipp Zabel <pza@xxxxxxxxxxxxxx> wrote:
> [...]
> > > because the register layout was greatly simplified for the newer SoCs
> > > (for which there is reset-intel) compared to the older ones
> > > (reset-lantiq).
> > > Dilip's suggestion (in my own words) is that you take his new
> > > reset-intel driver, then we will work on porting reset-lantiq over to
> > > that so in the end we can drop the reset-lantiq driver.
> > Just to be sure, you are suggesting to add support for the current
> > lantiq,reset binding to the reset-intel driver at a later point? I
> > see no reason not to do that, but I'm also not quite sure what the
> > benefit will be over just keeping reset-lantiq as is?
> according to Chuan and Dilip the current reset-lantiq implementation
> is wrong [0].
> my understanding is that the Lantiq and Intel LGM reset controllers
> are identical except:
> - the Lantiq variant uses a weird register layout (reset and status
> registers not at consecutive offsets)
> - the bits of the reset and status registers sometimes don't match on
> the Lantiq variant
> - the Intel variant has a dedicated registers area for the reset
> controller registers, while the Lantiq variant mixes them with various
> other functionality (for example: USB2 PHYs)
>
> > > This approach means more work for me (as I am probably the one who
> > > then has to do the work to port reset-lantiq over to reset-intel).
> > More work than what alternative?
> compared to "fixing" the existing reset-lantiq driver (reset callback)
> and then (instead of adding a new driver) integrating Intel LGM
> support into reset-lantiq

Integrating Intel LGM support into reset-lantiq boils down to re-writing 
reset-lantiq driver as intel-reset driver and adding Lantiq variant 
support. Why because reset-lantiq driver is not according to hardware 
design[1].

I see the final best solution is to integrate Lantiq variant driver to 
intel-reset driver.[1]
I hope you guys are ok with it. Please let me know your view.


Regards,
Dilip

[1]: https://www.spinics.net/lists/devicetree/msg308930.html

> > > I'm happy to do that work if you think that it's worth following this
> > > approach.  So I want your opinion on this before I spend any effort on
> > > porting reset-lantiq over to reset-intel.
> > Reset drivers are typically so simple, I'm not quite sure whether it is
> > worth to integrate multiple drivers if it complicates matters too much.
> > In this case though I expect it would just be adding support for a
> > custom .of_xlate and lantiq specific register property parsing?
> yes, that's how I understand the Lantiq and Intel reset controllers:
> - reset/status/assert/deassert callbacks would be shared across all variants
> - register parsing and of_xlate are SoC specific
>
>
> Martin
>
>
> [0] https://www.spinics.net/lists/devicetree/msg305951.html