Re: [PATCH] pinctrl: msm: Add support for MSM TLMM pinmux

[Hanumant Singh]

On 7/31/2013 5:17 PM, Hanumant Singh wrote:
> On 7/31/2013 2:06 PM, Stephen Warren wrote:
> > On 07/31/2013 01:46 PM, Hanumant Singh wrote:
> > > On 7/30/2013 8:59 PM, Stephen Warren wrote:
> > > > On 07/30/2013 06:13 PM, Hanumant Singh wrote:
> > > > > On 7/30/2013 5:08 PM, Stephen Warren wrote:
> > > > > > On 07/30/2013 06:01 PM, Hanumant Singh wrote:
> > > > > > > On 7/30/2013 2:22 PM, Stephen Warren wrote:
> > > > > > > > On 07/30/2013 03:10 PM, hanumant wrote:
> > > > > > > > ...
> > > > > > > > > We actually have the same TLMM pinmux used by several socs of a
> > > > > > > > > family.
> > > > > > > > > The number of pins on each soc may vary.
> > > > > > > > > Also a given soc gets used in a number of boards.
> > > > > > > > > The device tree for a given soc is split into the different boards
> > > > > > > > > that
> > > > > > > > > its in ie the boards inherit a common soc.dtsi but have separate
> > > > > > > > > dts.
> > > > > > > > > The boards for the same soc may use different pin groups for
> > > > > > > > > accomplishing a function, since we have multiple i2c, spi uart etc
> > > > > > > > > peripheral instances on a soc. A different instance of each of the
> > > > > > > > > above
> > > > > > > > > peripherals, can be used in different boards, utilizing different
> > > > > > > > > or subset of same pin groups.
> > > > > > > > > Thus I would need to have multiple C files for one soc, based
> > > > > > > > > on the
> > > > > > > > > boards that it goes into.
> > > > > > > >
> > > > > > > > The pinctrl driver should be exposing the raw capabilities of
> > > > > > > > the HW.
> > > > > > > > All the board-specific configuration should be expressed in DT.
> > > > > > > > So, the
> > > > > > > > driver shouldn't have to know anything about different boards at
> > > > > > > > compile-time.
> > > > > > > I agree, so I wanted to keep the pin grouping information in DT, we
> > > > > > > already have a board based differentiation of dts files in DT,
> > > > > > > for the
> > > > > > > same soc.
> > > > > >
> > > > > > That's the opposite of what I was saying. Pin groups are a feature of
> > > > > > the SoC design, not the board.
> > > > > Sorry I guess I wasn't clear.
> > > > > Right now I have a soc-pinctrl.dtsi containing pin groupings.
> > > > > This will be "inherited" by soc-boardtype.dts.
> > > > > The pinctrl client device nodes in soc-boardtype.dts will point to pin
> > > > > groupings in soc-pinctrl.dtsi that are valid for that particular
> > > > > boardtype.
> > > > > Is this a valid design?
> > > >
> > > > OK, so you have two types of child node inside the pinctrl DT node;
> > > > some
> > > > define the pin groups the SoC has (in soc.dtsi) and some define pinctrl
> > > > states that reference the pin group nodes and are referenced by the
> > > > client nodes.
> > > >
> > > > That's probably fine. However, I'd still question putting the pin group
> > > > nodes in DT at all; I'm not convinced it's better than just putting
> > > > those into the driver itself. You end up with the same data tables
> > > > after
> > > > parsing the DT anyway.
> > >
> > > Any feedback for the rest of the patch?
> >
> > I'm certainly waiting for this aspect of the patch to be resolved; I
> > think it will impact the rest of the patch so much that it's not worth
> > reviewing until we decide on where to represent the pin groups (some DT
> > parsing could would be removed if we put the pin group definitions into
> > the driver, hence wouldn't need to be reviewed, and likewise there's be
> > some new tables to review).
>
> I am trying to look at examples of what you are suggesting.
> I was looking at the exynos implementation, and just from a brief glance
> it seems like there too the pin grouping is being specified in the
> device tree, using what looks like labels of the pins.
> The labels are matched to group structures in soc specific files?
>
> By having the pin groupings in DT I am able to reuse the driver without
> any SOC based code bloat.
> As I mentioned earlier, we have entire families of SOCs using the same
> TLMM hardware.
> Its not a guarantee that for a given TLMM version,
> the pin groupings on that hardware are the same for every SOC that its
> in. Its infact most likely that I wont be able to use the pin groupings
> from one SOC to the next even if they both use the same TLMM.
> It will very quickly lead to a bloat of
> pinctrl-<msm_soc>.c (containing the pin groupings replicated for each soc)
> which use TLMM version specific register programming implementation
> pinctrl-tlmm-<version>.c
> and the DT parsing and interface to framework (which remains unchanged).
> pinctrl-msm.c.
>
> Thanks
> Hanumant

Any comments on this?

Thanks
Hanumant


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