Re: [RFC PATCH 1/4] dt-binding: i2c: add generic properties for GPIO bus recovery

From: Codrin.Ciubotariu
Date: Mon Jul 27 2020 - 06:45:04 EST

On 24.07.2020 23:52, Russell King - ARM Linux admin wrote:
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> On Fri, Jul 24, 2020 at 09:39:13PM +0200, Wolfram Sang wrote:
>> On Sun, Jul 05, 2020 at 11:19:18PM +0200, Wolfram Sang wrote:
>>>> +- pinctrl
>>>> + add extra pinctrl to configure SCL/SDA pins to GPIO function for bus
>>>> + recovery, call it "gpio" or "recovery" state
>>> I think we should stick with "gpio" only. That is what at91 and imx have
>>> in their bindings. pxa uses "recovery" as a pinctrl state name but I
>>> can't find any further use or documentation of that. PXA is not fully
>>> converted to the best of my knowledge, so maybe it is no problem for PXA
>>> to switch to "gpio", too? We should ask Russell King (cced).
> Fully converted to what? The generic handling where the i2c core layer
> handles everything to do with recovery, including the switch between
> modes?
> i2c-pxa _intentionally_ carefully handles the switch between i2c mode and
> GPIO mode, and I don't see a generic driver doing that to avoid causing
> any additional glitches on the bus. Given the use case that this recovery
> is targetted at, avoiding glitches is very important to keep.

Why is it not possbile to handle glitches in a generic way? I guess it
depends on the pinctl, but we could treat a worst-case scenario to
assure the switch between states is done properly.

>>> Russell, do you object naming the pinctrl state for bus recovery in
>>> the pxa i2c driver from "recovery" to "gpio"?
>> No response, so far. I suggest now to support the "recovery" naming but
>> mark it as deprecated. Opinions?
> I don't have a preference on the exact naming.
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