Re: pinctrl: single: Cannot disable bias - PIN_CONFIG_BIAS_DISABLE not handled

[Tony Lindgren <tony@xxxxxxxxxxx>]

Hi,

* Matthijs Kooijman <matthijs@xxxxxxxx> [240228 12:04]:
> While figuring out why bias-setting on the beaglebone black did not
> work, I noticed what looks like a bug in the pinctrl-single driver,
> preventing it from disabling a bias once enabled.
> 
> The short version is: It handles pin_config_set by looking up the requested
> setting in a DT-defined lookup table, which defines what bits correspond to
> each setting. For PIN_CONFIG_BIAS_DISABLE, this never works since that setting
> is never defined in the lookup table (so the code that exists to handle this
> setting is never actually executed).

OK

> It seems this code has been broken since it was first introduced in
> commit 9dddb4df90d1 (pinctrl: single: support generic pinconf).
> 
> An obvious fix for this would be to lift the handling for
> PIN_CONFIG_BIAS_DISABLE out of the inner loop, running that instead of
> the inner loop in that case.

Maybe post a suggested patch for Haojian to look at?

> Note that I have not verified my analysis of the code by testing. I did
> confirm that if I define the (what I think is) proper DT definitions for
> bias control for the beaglebone black board, I can enable bias, but not
> disable them, but I cannot rule out that that problem has a different
> cause. I also do not have a good toolchain setup for compiling custom
> kernels for this setup (and limited time for setting up one), so I do
> not expect to be able to provide more testing or a patch anytime soon.

The buildall script should allow you to easily build a cross compiler
on pretty much any current Linux host. I think this is the current
git tree for it:

https://github.com/nathanchance/buildall

Seems like buildall should be hosted at kernel.org but I don't know the
details, so adding Nathan to Cc too.

Regards,

Tony