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259b93b21a
Probing of regulators can be a slow operation and can contribute to slower boot times. This is especially true if a regulator is turned on at probe time (with regulator-boot-on or regulator-always-on) and the regulator requires delays (off-on-time, ramp time, etc). While the overall kernel is not ready to switch to async probe by default, as per the discussion on the mailing lists [1] it is believed that the regulator subsystem is in good shape and we can move regulator drivers over wholesale. There is no way to just magically opt in all regulators (regulators are just normal drivers like platform_driver), so we set PROBE_PREFER_ASYNCHRONOUS for all regulators found in 'drivers/regulator' individually. Given the number of drivers touched and the impossibility to test this ahead of time, it wouldn't be shocking at all if this caused a regression for someone. If there is a regression caused by this patch, it's likely to be one of the cases talked about in [1]. As a "quick fix", drivers involved in the regression could be fixed by changing them to PROBE_FORCE_SYNCHRONOUS. That being said, the correct fix would be to directly fix the problem that caused the issue with async probe. The approach here follows a similar approach that was used for the mmc subsystem several years ago [2]. In fact, I ran nearly the same python script to auto-generate the changes. The only thing I changed was to search for "i2c_driver", "spmi_driver", and "spi_driver" in addition to "platform_driver". [1] https://lore.kernel.org/r/06db017f-e985-4434-8d1d-02ca2100cca0@sirena.org.uk [2] https://lore.kernel.org/r/20200903232441.2694866-1-dianders@chromium.org/ Signed-off-by: Douglas Anderson <dianders@chromium.org> Link: https://lore.kernel.org/r/20230316125351.1.I2a4677392a38db5758dee0788b2cea5872562a82@changeid Signed-off-by: Mark Brown <broonie@kernel.org>
92 lines
2.1 KiB
C
92 lines
2.1 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* dummy.c
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*
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* Copyright 2010 Wolfson Microelectronics PLC.
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*
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* Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
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*
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* This is useful for systems with mixed controllable and
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* non-controllable regulators, as well as for allowing testing on
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* systems with no controllable regulators.
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*/
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#include <linux/err.h>
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#include <linux/export.h>
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#include <linux/platform_device.h>
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#include <linux/regulator/driver.h>
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#include <linux/regulator/machine.h>
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#include "dummy.h"
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struct regulator_dev *dummy_regulator_rdev;
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static const struct regulator_init_data dummy_initdata = {
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.constraints = {
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.always_on = 1,
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},
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};
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static const struct regulator_ops dummy_ops;
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static const struct regulator_desc dummy_desc = {
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.name = "regulator-dummy",
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.id = -1,
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.type = REGULATOR_VOLTAGE,
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.owner = THIS_MODULE,
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.ops = &dummy_ops,
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};
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static int dummy_regulator_probe(struct platform_device *pdev)
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{
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struct regulator_config config = { };
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int ret;
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config.dev = &pdev->dev;
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config.init_data = &dummy_initdata;
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dummy_regulator_rdev = devm_regulator_register(&pdev->dev, &dummy_desc,
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&config);
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if (IS_ERR(dummy_regulator_rdev)) {
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ret = PTR_ERR(dummy_regulator_rdev);
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pr_err("Failed to register regulator: %d\n", ret);
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return ret;
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}
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return 0;
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}
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static struct platform_driver dummy_regulator_driver = {
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.probe = dummy_regulator_probe,
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.driver = {
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.name = "reg-dummy",
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.probe_type = PROBE_PREFER_ASYNCHRONOUS,
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},
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};
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static struct platform_device *dummy_pdev;
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void __init regulator_dummy_init(void)
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{
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int ret;
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dummy_pdev = platform_device_alloc("reg-dummy", -1);
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if (!dummy_pdev) {
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pr_err("Failed to allocate dummy regulator device\n");
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return;
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}
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ret = platform_device_add(dummy_pdev);
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if (ret != 0) {
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pr_err("Failed to register dummy regulator device: %d\n", ret);
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platform_device_put(dummy_pdev);
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return;
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}
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ret = platform_driver_register(&dummy_regulator_driver);
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if (ret != 0) {
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pr_err("Failed to register dummy regulator driver: %d\n", ret);
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platform_device_unregister(dummy_pdev);
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}
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}
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