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8619909b38
Sometimes I get a NULL pointer dereference at boot time in kobject_get()
with the following call stack:
anatop_regulator_probe()
devm_regulator_register()
regulator_register()
regulator_resolve_supply()
kobject_get()
By placing some extra BUG_ON() statements I could verify that this is
raised because probing of the 'dummy' regulator driver is not completed
('dummy_regulator_rdev' is still NULL).
In the JTAG debugger I can see that dummy_regulator_probe() and
anatop_regulator_probe() can be run by different kernel threads
(kworker/u4:*). I haven't further investigated whether this can be
changed or if there are other possibilities to force synchronization
between these two probe routines. On the other hand I don't expect much
boot time penalty by probing the 'dummy' regulator synchronously.
Cc: stable@vger.kernel.org
Fixes: 259b93b21a ("regulator: Set PROBE_PREFER_ASYNCHRONOUS for drivers that existed in 4.14")
Signed-off-by: Christian Eggers <ceggers@arri.de>
Link: https://patch.msgid.link/20250311091803.31026-1-ceggers@arri.de
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_FORCE_SYNCHRONOUS,
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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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