Re: [PATCH v3 1/2] pinctrl: qcom: sc8180x: drop the use of tiles

[Shawn Guo <shawn.guo@linaro.org>]

On Mon, Mar 08, 2021 at 09:42:43PM -0600, Bjorn Andersson wrote:
> On Mon 08 Mar 20:56 CST 2021, Shawn Guo wrote:
> 
> > On Mon, Mar 08, 2021 at 07:08:00PM -0600, Bjorn Andersson wrote:
> > > On Thu 04 Mar 00:05 CST 2021, Shawn Guo wrote:
> > > 
> > > > To support both ACPI and DT, it makes more sense to not use tiles for
> > > > pinctrl-sc8180x driver, as ACPI table describes TLMM block with one
> > > > single memory resource.  Since DTS of SC8180X hasn't landed, there is
> > > > still chance to align DT description with ACPI.
> > > > 
> > > 
> > > I don't like the idea that we make up addresses to put in the DT to fit
> > > what was put in the DSDT. It is 3 different memory regions, with things
> > > in-between that Linux shouldn't touch.
> > 
> > This is not a new idea but something pinctrl-sdm845 has been doing for
> > years.  And IMHO, it's not a bad idea but a reasonable compromise.
> > 
> 
> SDM845 was the first platform where the previous contiguous TLMM block
> was split up in tiles, at the time we didn't see a need to split it up.
> 
> But then we hit QCS404 (iirc) where one of the tiles was way off and
> concluded that we needed the DT binding to actually represent the
> hardware - so the tiles concept was introduced.
> 
> Unfortunately introducing the tiles back into sdm845 would cause issues
> with existing DT, so that has not happened.
> 
> > > Isn't it possible to during ACPI probe take reg 0 and register the 3
> > > named regions instead?
> > 
> > It is possible.  But let's see what it takes.  We will need to have some
> > quirk handling in the ACPI core to detect TLMM device on Flex 5G
> > machine, and then override the memory resource registration for that
> > device.  Myself is not even convinced this is a good solution, not
> > mentioning whether ACPI maintainers will accept it.
> > 
> 
> I don't think this quirk should belong in the core. Can't you massage
> the resources once you're in the probe function in pinctrl-sc8180x.c? Or
> the platform resources can't be modified when we reach that point?

Okay, I misread your comment.  Yes, we can massage the resources, but
it's a bit tricky.  It took me hours get it right.  Anyway, I will send
it out for review.  Hopefully we can agree on one solution out of three
I have worked out.

Shawn