ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 208 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-waveshare-dsi.c b/drivers/gpio/gpio-waveshare-dsi.c
new file mode 100644
index 000000000..38f52351b
--- /dev/null
+++ b/drivers/gpio/gpio-waveshare-dsi.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Waveshare International Limited
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/fb.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+/* I2C registers of the microcontroller. */
+#define REG_TP		0x94
+#define REG_LCD		0x95
+#define REG_PWM		0x96
+#define REG_SIZE	0x97
+#define REG_ID		0x98
+#define REG_VERSION	0x99
+
+enum {
+	GPIO_AVDD = 0,
+	GPIO_PANEL_RESET = 1,
+	GPIO_BL_ENABLE = 2,
+	GPIO_IOVCC = 4,
+	GPIO_VCC = 8,
+	GPIO_TS_RESET = 9,
+};
+
+#define NUM_GPIO 16
+
+struct waveshare_gpio {
+	struct mutex dir_lock;
+	struct mutex pwr_lock;
+	struct regmap *regmap;
+	u16 poweron_state;
+
+	struct gpio_chip gc;
+};
+
+static const struct regmap_config waveshare_gpio_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = REG_VERSION,
+};
+
+static int waveshare_gpio_get(struct waveshare_gpio *state, unsigned int offset)
+{
+	u16 pwr_state;
+
+	guard(mutex)(&state->pwr_lock);
+	pwr_state = state->poweron_state & BIT(offset);
+
+	return !!pwr_state;
+}
+
+static int waveshare_gpio_set(struct waveshare_gpio *state, unsigned int offset, int value)
+{
+	u16 last_val;
+	int err;
+
+	guard(mutex)(&state->pwr_lock);
+
+	last_val = state->poweron_state;
+	if (value)
+		last_val |= BIT(offset);
+	else
+		last_val &= ~BIT(offset);
+
+	state->poweron_state = last_val;
+
+	err = regmap_write(state->regmap, REG_TP, last_val >> 8);
+	if (!err)
+		err = regmap_write(state->regmap, REG_LCD, last_val & 0xff);
+
+	return err;
+}
+
+static int waveshare_gpio_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int waveshare_gpio_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+	struct waveshare_gpio *state = gpiochip_get_data(gc);
+
+	return waveshare_gpio_get(state, offset);
+}
+
+static int waveshare_gpio_gpio_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	struct waveshare_gpio *state = gpiochip_get_data(gc);
+
+	return waveshare_gpio_set(state, offset, value);
+}
+
+static int waveshare_gpio_update_status(struct backlight_device *bl)
+{
+	struct waveshare_gpio *state = bl_get_data(bl);
+	int brightness = backlight_get_brightness(bl);
+
+	waveshare_gpio_set(state, GPIO_BL_ENABLE, brightness);
+
+	return regmap_write(state->regmap, REG_PWM, brightness);
+}
+
+static const struct backlight_ops waveshare_gpio_bl = {
+	.update_status = waveshare_gpio_update_status,
+};
+
+static int waveshare_gpio_probe(struct i2c_client *i2c)
+{
+	struct backlight_properties props = {};
+	struct waveshare_gpio *state;
+	struct device *dev = &i2c->dev;
+	struct backlight_device *bl;
+	struct regmap *regmap;
+	unsigned int data;
+	int ret;
+
+	state = devm_kzalloc(dev, sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	ret = devm_mutex_init(dev, &state->dir_lock);
+	if (ret)
+		return ret;
+
+	ret = devm_mutex_init(dev, &state->pwr_lock);
+	if (ret)
+		return ret;
+
+	regmap = devm_regmap_init_i2c(i2c, &waveshare_gpio_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap), "Failed to allocate register map\n");
+
+	state->regmap = regmap;
+	i2c_set_clientdata(i2c, state);
+
+	ret = regmap_read(regmap, REG_ID, &data);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to read register\n");
+
+	dev_dbg(dev, "waveshare panel hw id = 0x%x\n", data);
+
+	ret = regmap_read(regmap, REG_SIZE, &data);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to read register\n");
+
+	dev_dbg(dev, "waveshare panel size = %d\n", data);
+
+	ret = regmap_read(regmap, REG_VERSION, &data);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to read register\n");
+
+	dev_dbg(dev, "waveshare panel mcu version = 0x%x\n", data);
+
+	ret = waveshare_gpio_set(state, GPIO_TS_RESET, 1);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to program GPIOs\n");
+
+	msleep(20);
+
+	state->gc.parent = dev;
+	state->gc.label = i2c->name;
+	state->gc.owner = THIS_MODULE;
+	state->gc.base = -1;
+	state->gc.ngpio = NUM_GPIO;
+
+	/* it is output only */
+	state->gc.get = waveshare_gpio_gpio_get;
+	state->gc.set = waveshare_gpio_gpio_set;
+	state->gc.get_direction = waveshare_gpio_gpio_get_direction;
+	state->gc.can_sleep = true;
+
+	ret = devm_gpiochip_add_data(dev, &state->gc, state);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to create gpiochip\n");
+
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = 255;
+	props.brightness = 255;
+	bl = devm_backlight_device_register(dev, dev_name(dev), dev, state,
+					    &waveshare_gpio_bl, &props);
+	return PTR_ERR_OR_ZERO(bl);
+}
+
+static const struct of_device_id waveshare_gpio_dt_ids[] = {
+	{ .compatible = "waveshare,dsi-touch-gpio" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, waveshare_gpio_dt_ids);
+
+static struct i2c_driver waveshare_gpio_regulator_driver = {
+	.driver = {
+		.name = "waveshare-regulator",
+		.of_match_table = of_match_ptr(waveshare_gpio_dt_ids),
+	},
+	.probe = waveshare_gpio_probe,
+};
+
+module_i2c_driver(waveshare_gpio_regulator_driver);
+
+MODULE_DESCRIPTION("GPIO controller driver for Waveshare DSI touch panels");
+MODULE_LICENSE("GPL");