Re: [PATCH v11 1/4] dt-bindings: pinctrl: mt8195: add rsel define

[zhiyong.tao <zhiyong.tao@mediatek.com>]

On Mon, 2021-09-06 at 16:20 +0800, Chen-Yu Tsai wrote:
> On Sat, Sep 4, 2021 at 4:40 PM zhiyong.tao <zhiyong.tao@mediatek.com>
> wrote:
> > 
> > On Thu, 2021-09-02 at 11:35 +0800, Chen-Yu Tsai wrote:
> > > On Thu, Sep 2, 2021 at 10:54 AM zhiyong.tao <
> > > zhiyong.tao@mediatek.com
> > > > wrote:
> > > > 
> > > > On Wed, 2021-09-01 at 12:35 +0800, Chen-Yu Tsai wrote:
> > > > > On Mon, Aug 30, 2021 at 8:36 AM Zhiyong Tao <
> > > > > zhiyong.tao@mediatek.com> wrote:
> > > > > > 
> > > > > > This patch adds rsel define for mt8195.
> > > > > > 
> > > > > > Signed-off-by: Zhiyong Tao <zhiyong.tao@mediatek.com>
> > > > > > ---
> > > > > >  include/dt-bindings/pinctrl/mt65xx.h | 9 +++++++++
> > > > > >  1 file changed, 9 insertions(+)
> > > > > > 
> > > > > > diff --git a/include/dt-bindings/pinctrl/mt65xx.h
> > > > > > b/include/dt-
> > > > > > bindings/pinctrl/mt65xx.h
> > > > > > index 7e16e58fe1f7..f5934abcd1bd 100644
> > > > > > --- a/include/dt-bindings/pinctrl/mt65xx.h
> > > > > > +++ b/include/dt-bindings/pinctrl/mt65xx.h
> > > > > > @@ -16,6 +16,15 @@
> > > > > >  #define MTK_PUPD_SET_R1R0_10 102
> > > > > >  #define MTK_PUPD_SET_R1R0_11 103
> > > > > > 
> > > > > > +#define MTK_PULL_SET_RSEL_000  200
> > > > > > +#define MTK_PULL_SET_RSEL_001  201
> > > > > > +#define MTK_PULL_SET_RSEL_010  202
> > > > > > +#define MTK_PULL_SET_RSEL_011  203
> > > > > > +#define MTK_PULL_SET_RSEL_100  204
> > > > > > +#define MTK_PULL_SET_RSEL_101  205
> > > > > > +#define MTK_PULL_SET_RSEL_110  206
> > > > > > +#define MTK_PULL_SET_RSEL_111  207
> > > > > 
> > > > > Could you keep the spacing between constants tighter, or have
> > > > > no
> > > > > spacing
> > > > > at all? Like having MTK_PULL_SET_RSEL_000 defined as 104 and
> > > > > so
> > > > > on. This
> > > > > would reduce the chance of new macro values colliding with
> > > > > actual
> > > > > resistor
> > > > > values set in the datasheets, plus a contiguous space would
> > > > > be
> > > > > easy to
> > > > > rule as macros.
> > > > > 
> > > > > ChenYu
> > > > 
> > > > Hi chenyu,
> > > > By the current solution, it won't be mixed used by
> > > > MTK_PULL_SET_RSEL_XXX
> > > > and real  resistor value.
> > > > If user use MTK_PULL_SET_RSEL_XXX, They don't care the define
> > > > which
> > > > means how much resistor value.
> > > 
> > > What I meant was that by keeping the value space tight, we avoid
> > > the
> > > situation where in some new chip, one of the RSEL resistors
> > > happens
> > > to
> > > be 200 or 300 ohms. 100 is already taken, so there's nothing we
> > > can
> > > do if new designs actually do have 100 ohm settings.
> > > 
> > > > We think that we don't contiguous macro space for different
> > > > register.
> > > > It may increase code complexity to make having
> > > > MTK_PULL_SET_RSEL_000
> > > > defined as 104.
> > > 
> > > Can you elaborate? It is a simple range check and offset
> > > handling.
> > > Are
> > > you concerned that a new design would have R2R1R0 and you would
> > > like
> > > the macros to be contiguous?
> > > 
> > > BTW I don't quite get why decimal base values (100, 200, etc.)
> > > were
> > > chosen. One would think that binary bases are easier to handle in
> > > code.
> > > 
> > > 
> > > ChenYu
> > > 
> > 
> > Yes,we concerned that a new design would have R2R1R0 and we would
> > like
> > the macros to be contiguous in the feature. we reserve it.
> 
> I see. That makes sense. Do you expect to see R3 or even R4 in the
> future?
> Or put another way, do you expect to see resistor values of 150 or
> 200
> supported?
> 
> Maybe we could reserve 200 and start from 201 for the RSEL macros?
> 
> Some planning needs to be done here to avoid value clashes.
> 
> > We think that decimal and binary base values are the same for the
> > feature.
> 
> With decimal numbers you end up wasting a bit more space, since the
> hardware is always using binary values. I just found it odd, that's
> all.
> 
> ChenYu
> 
> > > > Thanks.

Hi ChenYu,

In the next version, we provide a solution which we discussed internal
to avoid value clashes.
 
The solution:
1. We will keep the define "MTK_PULL_SET_RSEL_000 200". It won't
change.

2. We will add a property in pio dtsi node, for example,
the property name is "rsel_resistance_in_si_unit".
We will add a flag "rsel_si_unit" in pinctrl device.
in probe function, we will identify the property name
"rsel_resistance_in_si_unit" to set the flag "rsel_si_unit" value.
So it can void value clashes.

3.We will provide the define "MTK_PULL_SET_RSEL_000 200" and si unit
two solution. users can support which solution by add property
"rsel_resistance_in_si_unit" in dts node or not.

Thanks.


> > > > 
> > > > > 
> > > > > >  #define MTK_DRIVE_2mA  2
> > > > > >  #define MTK_DRIVE_4mA  4
> > > > > >  #define MTK_DRIVE_6mA  6
> > > > > > --
> > > > > > 2.18.0
> > > > > > _______________________________________________
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> > > > > > Linux-mediatek@lists.infradead.org
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