Re: [PATCH v2 1/2] pinctrl: Allow a device to indicate when to force a state
From: Tony Lindgren <tony@atomide.com>
Date: 2017-11-29 17:45:07
Also in:
linux-gpio, lkml
* Florian Fainelli [off-list ref] [171129 17:37]:
On 11/29/2017 09:01 AM, Tony Lindgren wrote:quoted
* Florian Fainelli [off-list ref] [171102 23:18]:quoted
It may happen that a device needs to force applying a state, e.g: because it only defines one state of pin states (default) but loses power/register contents when entering low power modes. Add a pinctrl_dev::flags bitmask to help describe future quirks and define PINCTRL_FLG_FORCE_STATE as such a settable flag.It makes sense to tag the existing state with the context loss information as otherwise we'll be duplicating the state in the pinctrl driver potentially for hundreds of pins. Maybe this patch description should clarify that it's the pinctrl device restoring the pin state, not the pinctrl consumer devices? So maybe just "a pinctrl device needs to force apply a state" instead of just device above?It's a bit more involved than that, the pinctrl consumer device might want to restore a particular state by calling pinctrl_select_state(), however, because of the (p->state == state)check, the pinctrl provider driver has no chance of making that call do the actual HW programming.
Hmm but isn't it the pinctrl provider device losing context here? I think the restore of the pin state should somehow happen automatically by the pinctrl provider driver without a need for the pinctrl consumer drivers to do anything. Or what's the use case for pinctrl consumer driver wanting to store a pin? Regards, Tony