Messages in this thread | | | Date | Fri, 31 Oct 2014 18:36:10 +0100 | Subject | Re: [PATCH RFC v2 8/8] ARM: zynq: DT: Add pinctrl information | From | Linus Walleij <> |
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On Fri, Oct 31, 2014 at 5:57 PM, Sören Brinkmann <soren.brinkmann@xilinx.com> wrote: > On Fri, 2014-10-31 at 09:17AM +0100, Linus Walleij wrote:
>> Again it seems to be a sequencing problem. And device tree is >> not good at sequences, therefore all states should be self-contained. > > I agree, but how would I define a pin with pull-up enabled and > tri-state disabled - assume the pin is currently in a random state that > can have those things set/not set arbitrarily.
I was more thinking as everything you don't enable explicitly in a state is per definition disabled.
So if you are in state A and tri-state is enabled there and you move to state B where pull-up is enabled, then tri-state should be disabled, since it is not explicitly enabled.
> I can't put bias-disable in DT since it would potentially disable both > and the pull-up enable would have only a transient effect.
Well look at the callback from the core:
int (*pin_config_set) (struct pinctrl_dev *pctldev, unsigned pin, unsigned long *configs, unsigned num_configs);
You get all configs in an array. The driver can walk over the list and make informed decisions on what to do *BEFORE* poking any registers.
Avoiding transients as you describe is part of why the callback looks as it does. This is why every driver has its own for-loop.
> I can't do the sequencing in the driver either. If I see pull-up enable, > I can't imply an effect on tri-state since I can't know whether there > was/will be a tri-state property that sets it as well.
If you define that each state is self-contained you can.
Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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