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ef0eebc051
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>
100 lines
2.5 KiB
C
100 lines
2.5 KiB
C
/*
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* Driver core interface to the pinctrl subsystem.
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*
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* Copyright (C) 2012 ST-Ericsson SA
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* Written on behalf of Linaro for ST-Ericsson
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* Based on bits of regulator core, gpio core and clk core
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*
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* Author: Linus Walleij <linus.walleij@linaro.org>
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*
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* License terms: GNU General Public License (GPL) version 2
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*/
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#include <linux/device.h>
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#include <linux/pinctrl/devinfo.h>
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#include <linux/pinctrl/consumer.h>
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#include <linux/slab.h>
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/**
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* pinctrl_bind_pins() - called by the device core before probe
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* @dev: the device that is just about to probe
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*/
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int pinctrl_bind_pins(struct device *dev)
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{
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int ret;
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dev->pins = devm_kzalloc(dev, sizeof(*(dev->pins)), GFP_KERNEL);
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if (!dev->pins)
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return -ENOMEM;
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dev->pins->p = devm_pinctrl_get(dev);
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if (IS_ERR(dev->pins->p)) {
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dev_dbg(dev, "no pinctrl handle\n");
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ret = PTR_ERR(dev->pins->p);
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goto cleanup_alloc;
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}
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dev->pins->default_state = pinctrl_lookup_state(dev->pins->p,
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PINCTRL_STATE_DEFAULT);
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if (IS_ERR(dev->pins->default_state)) {
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dev_dbg(dev, "no default pinctrl state\n");
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ret = 0;
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goto cleanup_get;
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}
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dev->pins->init_state = pinctrl_lookup_state(dev->pins->p,
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PINCTRL_STATE_INIT);
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if (IS_ERR(dev->pins->init_state)) {
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/* Not supplying this state is perfectly legal */
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dev_dbg(dev, "no init pinctrl state\n");
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ret = pinctrl_select_state(dev->pins->p,
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dev->pins->default_state);
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} else {
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ret = pinctrl_select_state(dev->pins->p, dev->pins->init_state);
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}
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if (ret) {
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dev_dbg(dev, "failed to activate initial pinctrl state\n");
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goto cleanup_get;
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}
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#ifdef CONFIG_PM
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/*
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* If power management is enabled, we also look for the optional
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* sleep and idle pin states, with semantics as defined in
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* <linux/pinctrl/pinctrl-state.h>
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*/
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dev->pins->sleep_state = pinctrl_lookup_state(dev->pins->p,
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PINCTRL_STATE_SLEEP);
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if (IS_ERR(dev->pins->sleep_state))
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/* Not supplying this state is perfectly legal */
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dev_dbg(dev, "no sleep pinctrl state\n");
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dev->pins->idle_state = pinctrl_lookup_state(dev->pins->p,
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PINCTRL_STATE_IDLE);
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if (IS_ERR(dev->pins->idle_state))
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/* Not supplying this state is perfectly legal */
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dev_dbg(dev, "no idle pinctrl state\n");
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#endif
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return 0;
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/*
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* If no pinctrl handle or default state was found for this device,
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* let's explicitly free the pin container in the device, there is
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* no point in keeping it around.
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*/
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cleanup_get:
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devm_pinctrl_put(dev->pins->p);
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cleanup_alloc:
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devm_kfree(dev, dev->pins);
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dev->pins = NULL;
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/* Only return deferrals */
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if (ret != -EPROBE_DEFER)
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ret = 0;
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return ret;
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}
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