For pinctrl the "default" state is applied to pins before the driver's probe function is called. This is normally a sensible thing to do, but in some cases can cause problems. That's because the pins will change state before the driver is given a chance to program how those pins should behave. As an example you might have a regulator that is controlled by a PWM (output high = high voltage, output low = low voltage). The firmware might leave this pin as driven high. If we allow the driver core to reconfigure this pin as a PWM pin before the PWM's probe function runs then you might end up running at too low of a voltage while we probe. Let's introudce a new "init" state. If this is defined we'll set pinctrl to this state before probe and then "default" after probe (unless the driver explicitly changed states already). An alternative idea that was thought of was to use the pre-existing "sleep" or "idle" states and add a boolean property that we should start in that mode. This was not done because the "init" state is needed for correctness and those other states are only present (and only transitioned in to and out of) when (optional) power management is enabled. Changes in v3: - Moved declarations to pinctrl/devinfo.h - Fixed author/SoB Changes in v2: - Added comment to pinctrl_init_done() as per Linus W.
Showing the changes to include/linux/pinctrl (2 of 5 files). Show all
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| @@ -24,10 +24,14 @@ · 23 unmodified lines | ||
| 24 | 24 | * struct dev_pin_info - pin state container for devices |
| 25 | 25 | * @p: pinctrl handle for the containing device |
| 26 | 26 | * @default_state: the default state for the handle, if found |
| 27 | + * @init_state: the state at probe time, if found | |
| 28 | + * @sleep_state: the state at suspend time, if found | |
| 29 | + * @idle_state: the state at idle (runtime suspend) time, if found | |
| 27 | 30 | */ |
| 28 | 31 | struct dev_pin_info { |
| 29 | 32 | struct pinctrl *p; |
| 30 | 33 | struct pinctrl_state *default_state; |
| 34 | + struct pinctrl_state *init_state; | |
| 31 | 35 | #ifdef CONFIG_PM |
| 32 | 36 | struct pinctrl_state *sleep_state; |
| 33 | 37 | struct pinctrl_state *idle_state; |
| @@ -35,6 +39,7 @@ struct dev_pin_info { · 1 unmodified line | ||
| 35 | 39 | }; |
| 36 | 40 | |
| 37 | 41 | extern int pinctrl_bind_pins(struct device *dev); |
| 42 | +extern int pinctrl_init_done(struct device *dev); | |
| 38 | 43 | |
| 39 | 44 | #else |
| 40 | 45 | |
| @@ -45,5 +50,10 @@ static inline int pinctrl_bind_pins(struct device *dev) · 4 unmodified lines | ||
| 45 | 50 | return 0; |
| 46 | 51 | } |
| 47 | 52 | |
| 53 | +static inline int pinctrl_init_done(struct device *dev) | |
| 54 | +{ | |
| 55 | + return 0; | |
| 56 | +} | |
| 57 | + | |
| 48 | 58 | #endif /* CONFIG_PINCTRL */ |
| 49 | 59 | #endif /* PINCTRL_DEVINFO_H */ |
| @@ -9,6 +9,13 @@ · 8 unmodified lines | ||
| 9 | 9 | * hogs to configure muxing and pins at boot, and also as a state |
| 10 | 10 | * to go into when returning from sleep and idle in |
| 11 | 11 | * .pm_runtime_resume() or ordinary .resume() for example. |
| 12 | + * @PINCTRL_STATE_INIT: normally the pinctrl will be set to "default" | |
| 13 | + * before the driver's probe() function is called. There are some | |
| 14 | + * drivers where that is not appropriate becausing doing so would | |
| 15 | + * glitch the pins. In those cases you can add an "init" pinctrl | |
| 16 | + * which is the state of the pins before drive probe. After probe | |
| 17 | + * if the pins are still in "init" state they'll be moved to | |
| 18 | + * "default". | |
| 12 | 19 | * @PINCTRL_STATE_IDLE: the state the pinctrl handle shall be put into |
| 13 | 20 | * when the pins are idle. This is a state where the system is relaxed |
| 14 | 21 | * but not fully sleeping - some power may be on but clocks gated for |
| @@ -20,5 +27,6 @@ · 5 unmodified lines | ||
| 20 | 27 | * ordinary .suspend() function. |
| 21 | 28 | */ |
| 22 | 29 | #define PINCTRL_STATE_DEFAULT "default" |
| 30 | +#define PINCTRL_STATE_INIT "init" | |
| 23 | 31 | #define PINCTRL_STATE_IDLE "idle" |
| 24 | 32 | #define PINCTRL_STATE_SLEEP "sleep" |