linux-kernel - Re: [PATCH v2 1/5] pinctrl: qcom: Add ipq8074 pinctrl driver

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Date:   Fri, 19 May 2017 22:54:30 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Varadarajan Narayanan <varada@...eaurora.org>,
        linus.walleij@...aro.org
Cc:     mark.rutland@....com, devicetree@...r.kernel.org,
        Manoharan Vijaya Raghavan <mraghava@...eaurora.org>,
        linux-gpio@...r.kernel.org, catalin.marinas@....com,
        mturquette@...libre.com, sjaganat@...eaurora.org,
        sboyd@...eaurora.org, linux-kernel@...r.kernel.org,
        will.deacon@....com, linux-clk@...r.kernel.org,
        david.brown@...aro.org, absahu@...eaurora.org, robh+dt@...nel.org,
        linux-arm-msm@...r.kernel.org, andy.gross@...aro.org,
        sricharan@...eaurora.org, linux-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/5] pinctrl: qcom: Add ipq8074 pinctrl driver

On Thu 18 May 01:39 PDT 2017, Varadarajan Narayanan wrote:

> 
> 
> On 5/18/2017 1:03 AM, Bjorn Andersson wrote:
> > On Mon 15 May 02:05 PDT 2017, Varadarajan Narayanan wrote:
> > 
> > > On 5/14/2017 9:53 AM, Bjorn Andersson wrote:
> > > > On Thu 11 May 03:33 PDT 2017, Varadarajan Narayanan wrote:
> > > > 
> > > > > On 5/11/2017 4:13 AM, Bjorn Andersson wrote:
> > > > > > On Thu 04 May 04:53 PDT 2017, Varadarajan Narayanan wrote:
> > [..]
> > > > > > > +	msm_mux_qpic_pad4,
> > > > > > 
> > > > > > What are qpic_pad and qpic_pad0 through qpic_pad8? Different functions,
> > > > > > alternative muxings...?
> > > > > 
> > > > > This is for the NAND and LCD display. The pins listed are the 9 data pins.
> > > > > 
> > > > 
> > > > Then you can describe them all as "qpic_pad" (or simply "qpic"?). (It's
> > > > possible to reference a partial group in the DTS, if that's necessary)
> > > 
> > > There are two sets of 9 pins, either of which can go to NAND or LCD.
> > > Will rename qpic_pad as qpic_a and qpic_pad[0-8] as qpic_b.
> > > Is that ok?
> > > 
> > 
> > So you have NAND and LCD hardware muxed to either "a" or "b" and then
> > you mux either "a" or "b" out onto actual pins?
> > 
> > How is this first mux configured?
> > 
> > I think the a/b scheme sounds reasonable, if above is how it works.
> 
> Sorry, I was wrong. I had misread the documentation.
> 
> There are 18 pins. 15 pins are common between LCD and NAND. The QPIC
> controller arbitrates between LCD and NAND. Of the remaining 4, 2 are for
> NAND and 2 are for LCD exclusively. We plan to group the qpic pins into 3
> groups namely, qpic_common, qpic_nand and qpic_lcd. Is that ok?
> 

If you consider that you are defining the available functions for this
pinmuxer and then define the sets of pins exposing these available
functions it does make sense to just name it "qpic".

I think that naming them _common, _lcd and _nand is just adding
confusion when it comes to writing the dts files.


@Linus, do you have a different preference here?

Regards,
Bjorn