Re: [PATCH v11 1/4] dt-bindings: i2c: Add CP2112 HID USB to SMBus Bridge

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Jun 06, 2024 at 11:24:38AM -0500, Danny Kaehn wrote:
> On Thu, Jun 06, 2024 at 09:18:59AM -0600, Rob Herring wrote:
> > On Wed, Jun 05, 2024 at 06:12:44PM -0500, Danny Kaehn wrote:

...

> > > +  i2c:
> > > +    description: The SMBus/I2C controller node for the CP2112
> > > +    $ref: /schemas/i2c/i2c-controller.yaml#
> > > +    unevaluatedProperties: false
> > > +
> > > +    properties:
> > > +      sda-gpios:
> > > +        maxItems: 1
> > > +
> > > +      scl-gpios:
> > > +        maxItems: 1
> > 
> > These are because I2C can be on any of the pins? It's a bit odd if they 
> > aren't used as gpios. Probably should be pinmux, but that's overkill for 
> > 2 pins.
> >
> 
> I'm beginning to realize now that this may be a bit non-standard, but it
> did solve a stuck bus issue under some conditions.
> 
> The CP2112's I2C controller is self-contained and can only be on the
> specific pins it is attached to (no pinmux, etc..).
> 
> In this case, these properties are ment to specify additional gpio pins
> which are connected to the SCL and SDA lines (this then also assumes those
> are configured to be open drain / inputs to not interfere with the bus
> during normal operation). This was inspired by what is done ini2c-imx.yaml,
> but I realize this is a bit different due to using external pins rather
> than pinmuxing to the GPIOs.
> 
> How I used this was to actually connect some of the CP2112's own GPIO pins
> to the SDA and SCL lines to be able to use those pins to recover the
> bus. This was able to solve a stuck bus under some real-world cases with
> the v2 of the CP2112 containing an errata which caused this
> semi-frequently.

Aren't they just for I²C recovery?

-- 
With Best Regards,
Andy Shevchenko