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authorDouglas Anderson <dianders@chromium.org>2015-10-20 21:15:06 -0700
committerLinus Walleij <linus.walleij@linaro.org>2015-10-27 11:24:23 +0100
commitef0eebc05130b0d22b0ea65c0cd014ee16fc89c7 (patch)
treeb40d2dbcd3ff1930c3bf03bba34cd7ef9496334f /drivers/base/pinctrl.c
parentbac7f4c1bf5e7c6ccd5bb71edc015b26c77f7460 (diff)
drivers/pinctrl: Add the concept of an "init" state
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. Signed-off-by: Douglas Anderson <dianders@chromium.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Tested-by: Caesar Wang <wxt@rock-chips.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/base/pinctrl.c')
-rw-r--r--drivers/base/pinctrl.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/drivers/base/pinctrl.c b/drivers/base/pinctrl.c
index 5fb74b43848e..076297592754 100644
--- a/drivers/base/pinctrl.c
+++ b/drivers/base/pinctrl.c
@@ -42,9 +42,20 @@ int pinctrl_bind_pins(struct device *dev)
goto cleanup_get;
}
- ret = pinctrl_select_state(dev->pins->p, dev->pins->default_state);
+ dev->pins->init_state = pinctrl_lookup_state(dev->pins->p,
+ PINCTRL_STATE_INIT);
+ if (IS_ERR(dev->pins->init_state)) {
+ /* Not supplying this state is perfectly legal */
+ dev_dbg(dev, "no init pinctrl state\n");
+
+ ret = pinctrl_select_state(dev->pins->p,
+ dev->pins->default_state);
+ } else {
+ ret = pinctrl_select_state(dev->pins->p, dev->pins->init_state);
+ }
+
if (ret) {
- dev_dbg(dev, "failed to activate default pinctrl state\n");
+ dev_dbg(dev, "failed to activate initial pinctrl state\n");
goto cleanup_get;
}