On Fri, 2014-10-31 at 10:40AM -0700, Sören Brinkmann wrote: > On Fri, 2014-10-31 at 06:36PM +0100, Linus Walleij wrote: > > On Fri, Oct 31, 2014 at 5:57 PM, Sören Brinkmann > > <soren.brinkm...@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. > > Okay, I guess that is possible. I find usage of the arguments more > elegant since it is more explicit and reduces code in the driver, but I > suspect it should work.
It does work with some limitation though. This was how I originally described a state in DT: pinctrl_uart1_default: pinctrl-uart1-default { common { groups = "uart1_10_grp"; function = "uart1"; bias-pull-up = <0>; slew-rate = <0>; io-standard = <1>; }; rx { pins = "MIO49"; bias-high-impedance = <1>; }; tx { pins = "MIO48"; bias-high-impedance = <0>; }; }; Now, I removed the arguments for tri-state and pull-up. The problem, this state is handled per-sub-node. I.e. one call to the cfg-set callback per node. I.e. I cannot split things in common, rx and tx, but I need to duplicate the pinconf props in rx and tx, resulting in: pinctrl_uart1_default: pinctrl-uart1-default { common { groups = "uart1_10_grp"; function = "uart1"; }; rx { pins = "MIO49"; slew-rate = <0>; io-standard = <1>; bias-high-impedance; }; tx { pins = "MIO48"; slew-rate = <0>; io-standard = <1>; }; }; In a nutshell, yes, it's possible to work without the arguments for pull-up or tri-state. But it adds complexity in the driver and the DT description. Sören -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/