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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/pinctrl
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/pinctrl')
-rw-r--r--drivers/pinctrl/core.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index 9638a00c67c2..2686a4450dfc 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1240,6 +1240,38 @@ int pinctrl_force_default(struct pinctrl_dev *pctldev)
}
EXPORT_SYMBOL_GPL(pinctrl_force_default);
+/**
+ * pinctrl_init_done() - tell pinctrl probe is done
+ *
+ * We'll use this time to switch the pins from "init" to "default" unless the
+ * driver selected some other state.
+ *
+ * @dev: device to that's done probing
+ */
+int pinctrl_init_done(struct device *dev)
+{
+ struct dev_pin_info *pins = dev->pins;
+ int ret;
+
+ if (!pins)
+ return 0;
+
+ if (IS_ERR(pins->init_state))
+ return 0; /* No such state */
+
+ if (pins->p->state != pins->init_state)
+ return 0; /* Not at init anyway */
+
+ if (IS_ERR(pins->default_state))
+ return 0; /* No default state */
+
+ ret = pinctrl_select_state(pins->p, pins->default_state);
+ if (ret)
+ dev_err(dev, "failed to activate default pinctrl state\n");
+
+ return ret;
+}
+
#ifdef CONFIG_PM
/**