RE: [PATCH v6 01/13] pinctrl: core: Add pinctrl_get_device()

[Biju Das <biju.das.jz@xxxxxxxxxxxxxx>]

Hi Andy, 

Thanks for the feedback.

> Subject: Re: [PATCH v6 01/13] pinctrl: core: Add pinctrl_get_device()
> 
> On Tue, Mar 7, 2023 at 10:13 AM Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> > > Subject: Re: [PATCH v6 01/13] pinctrl: core: Add
> > > pinctrl_get_device() Mon, Mar 06, 2023 at 09:00:02AM +0000, Biju Das
> kirjoitti:
> 
> ...
> 
> > > > Add pinctrl_get_device() to find a device handle associated with a
> > > > pincontrol group(i.e. by matching function name and group name for
> > > > a device). This device handle can then be used for finding match
> > > > for the pin output disable device that protects device against
> > > > short circuits on the pins.
> > >
> > > Not sure I understand the use case. Please, create a better commit
> message.
> >
> > OK, Basically pinmux_enable_setting allows exclusive access of pin to a
> device.
> > It won't allow multiple devices to claim a pin.
> 
> Which is correct. No? Show me the schematics of the real use case for that.
> 
> The owner of the pin is the host side. I can't imagine how the same pin is
> shared inside the SoC. Is it broken hardware design?

We are discussing usage of 

echo "fname gname" and you asked a question whether multiple devices can
claim a pin at the same time

and my answer is no.

as setting->data.mux will be unique for a pin and will be claimed by
device during commit state.

Am I missing anything here??

Cheers,
Biju

> 
> ...
> 
> > > Also it is missing the explanation why there will be no collisions
> > > when looking by the same pair of function and group name from different
> device.
> >
> > setting->data.mux will be unique for a pin. So there won't be a
> > setting->collision when
> > looking by the same pair of function and group name from different device.
> >
> > > (Always imagine that you have 2+ same IP blocks on the platform
> > > before doing any pin control core work. This will help you to design
> > > it properly. )
> 
> Not sure how the pair function_name group_name makes the device unique.

Do you agree Device handle + function_name +  group_name make it unique.

For pin outdisable we are making use of this 3 combination.
See the details.


This patch series adds support for controlling output disable function using
sysfs in a generic way as described below.

|    A     |    |     B      |    |     C     |    |     D        |  | E |
|user space|--->|pinctrl core|<-->|SoC pinctrl|<-->|Output disable|--|PWM|
|          |    |            |    |           |    |              |  |   |

A executes command to configure a pin group for pin output disable operation
  echo "fname gname conf conf_val" > configure

B parses the command and identifies the binding device associated with that
  pin group

C matches the binding device against the device registered by D for
  configuration operation

D matches the pin group and configure the pins for Output disable operation

Both D and E are linked together by dt(i.e. PWM channel linked with Output
 disable Port)

Cheers,
Biju