Re: [PATCH 1/2] dt-bindings: pinctrl: renesas,r9a09g077: Document pin configuration properties

Lad, Prabhakar
2025-12-12T11:12:00Z

Hi Linus,

Thank you for the review.

On Thu, Dec 11, 2025 at 12:00 AM Linus Walleij <linusw@kernel.org> wrote:
>
> Hi Lad,
>
> thanks for your patch!
>
> On Mon, Dec 8, 2025 at 7:01 PM Conor Dooley <conor@kernel.org> wrote:
> > On Mon, Dec 08, 2025 at 10:36:04AM +0000, Lad, Prabhakar wrote:
>
> > > > > > + slew-rate:
> > > > > > + enum: [0, 1]
> > > > >
> > > > > What are the meanings of "0" and "1" for slew rate? Why isn't this given
> > > > I'll add a description for it (0 = slow, 1 = fast) and the same values
> > > > are programmed in the register to configure the slew rate.
> > > >
> > > > > as the actual rates? The docs surely give more detail than just "slow"
> > > > > and "fast".
> > > > You mean to represent slew-rate in some sort of a unit?
> > > >
> > > Based on the comments from the HW team, there is no numerical
> > > definition to represent slow/fast It only defines a relative
> > > relationship.
>
> Then describe relative to what, so we can understand when to use
> which setting?
>
I have made a query regarding this to the HW team. I'll respond as
soon as I get any feedback.

> > > The current value is determined by the load on the external circuit
> > > and is not affected by the choice of drive strength.
> (...)
> > Remember, drive strength is the current that can be delivered through a
> > pin, not how much it is delivering at a given point in time.
>
> This seems to be the core of the misunderstanding here.
>
> The setting defines the cap. How much current *can* be delivered.
>
> If the pin controller had a fuse that would bust if we delivered too
> much current, this would be the grading of that fuse.
>
> It's the current where the driver stage(s) stop pushing in more
> electrons, it's a very real thing and does not depend on what the
> circuit look like.
>
> Pins usually have protected driver stages, so connecting an
> amperemeter directly to ground and driving the line high would
> actually give this value.
>
Agreed.

Cheers,
Prabhakar