From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- drivers/rtc/rtc-m48t86.c | 291 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 291 insertions(+) create mode 100644 drivers/rtc/rtc-m48t86.c (limited to 'drivers/rtc/rtc-m48t86.c') diff --git a/drivers/rtc/rtc-m48t86.c b/drivers/rtc/rtc-m48t86.c new file mode 100644 index 000000000..db3bdb171 --- /dev/null +++ b/drivers/rtc/rtc-m48t86.c @@ -0,0 +1,291 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * ST M48T86 / Dallas DS12887 RTC driver + * Copyright (c) 2006 Tower Technologies + * + * Author: Alessandro Zummo + * + * This drivers only supports the clock running in BCD and 24H mode. + * If it will be ever adapted to binary and 12H mode, care must be taken + * to not introduce bugs. + */ + +#include +#include +#include +#include +#include + +#define M48T86_SEC 0x00 +#define M48T86_SECALRM 0x01 +#define M48T86_MIN 0x02 +#define M48T86_MINALRM 0x03 +#define M48T86_HOUR 0x04 +#define M48T86_HOURALRM 0x05 +#define M48T86_DOW 0x06 /* 1 = sunday */ +#define M48T86_DOM 0x07 +#define M48T86_MONTH 0x08 /* 1 - 12 */ +#define M48T86_YEAR 0x09 /* 0 - 99 */ +#define M48T86_A 0x0a +#define M48T86_B 0x0b +#define M48T86_B_SET BIT(7) +#define M48T86_B_DM BIT(2) +#define M48T86_B_H24 BIT(1) +#define M48T86_C 0x0c +#define M48T86_D 0x0d +#define M48T86_D_VRT BIT(7) +#define M48T86_NVRAM(x) (0x0e + (x)) +#define M48T86_NVRAM_LEN 114 + +struct m48t86_rtc_info { + void __iomem *index_reg; + void __iomem *data_reg; +}; + +static unsigned char m48t86_readb(struct device *dev, unsigned long addr) +{ + struct m48t86_rtc_info *info = dev_get_drvdata(dev); + unsigned char value; + + writeb(addr, info->index_reg); + value = readb(info->data_reg); + + return value; +} + +static void m48t86_writeb(struct device *dev, + unsigned char value, unsigned long addr) +{ + struct m48t86_rtc_info *info = dev_get_drvdata(dev); + + writeb(addr, info->index_reg); + writeb(value, info->data_reg); +} + +static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm) +{ + unsigned char reg; + + reg = m48t86_readb(dev, M48T86_B); + + if (reg & M48T86_B_DM) { + /* data (binary) mode */ + tm->tm_sec = m48t86_readb(dev, M48T86_SEC); + tm->tm_min = m48t86_readb(dev, M48T86_MIN); + tm->tm_hour = m48t86_readb(dev, M48T86_HOUR) & 0x3f; + tm->tm_mday = m48t86_readb(dev, M48T86_DOM); + /* tm_mon is 0-11 */ + tm->tm_mon = m48t86_readb(dev, M48T86_MONTH) - 1; + tm->tm_year = m48t86_readb(dev, M48T86_YEAR) + 100; + tm->tm_wday = m48t86_readb(dev, M48T86_DOW); + } else { + /* bcd mode */ + tm->tm_sec = bcd2bin(m48t86_readb(dev, M48T86_SEC)); + tm->tm_min = bcd2bin(m48t86_readb(dev, M48T86_MIN)); + tm->tm_hour = bcd2bin(m48t86_readb(dev, M48T86_HOUR) & + 0x3f); + tm->tm_mday = bcd2bin(m48t86_readb(dev, M48T86_DOM)); + /* tm_mon is 0-11 */ + tm->tm_mon = bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1; + tm->tm_year = bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100; + tm->tm_wday = bcd2bin(m48t86_readb(dev, M48T86_DOW)); + } + + /* correct the hour if the clock is in 12h mode */ + if (!(reg & M48T86_B_H24)) + if (m48t86_readb(dev, M48T86_HOUR) & 0x80) + tm->tm_hour += 12; + + return 0; +} + +static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm) +{ + unsigned char reg; + + reg = m48t86_readb(dev, M48T86_B); + + /* update flag and 24h mode */ + reg |= M48T86_B_SET | M48T86_B_H24; + m48t86_writeb(dev, reg, M48T86_B); + + if (reg & M48T86_B_DM) { + /* data (binary) mode */ + m48t86_writeb(dev, tm->tm_sec, M48T86_SEC); + m48t86_writeb(dev, tm->tm_min, M48T86_MIN); + m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR); + m48t86_writeb(dev, tm->tm_mday, M48T86_DOM); + m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH); + m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR); + m48t86_writeb(dev, tm->tm_wday, M48T86_DOW); + } else { + /* bcd mode */ + m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC); + m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN); + m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR); + m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM); + m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH); + m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR); + m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW); + } + + /* update ended */ + reg &= ~M48T86_B_SET; + m48t86_writeb(dev, reg, M48T86_B); + + return 0; +} + +static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq) +{ + unsigned char reg; + + reg = m48t86_readb(dev, M48T86_B); + + seq_printf(seq, "mode\t\t: %s\n", + (reg & M48T86_B_DM) ? "binary" : "bcd"); + + reg = m48t86_readb(dev, M48T86_D); + + seq_printf(seq, "battery\t\t: %s\n", + (reg & M48T86_D_VRT) ? "ok" : "exhausted"); + + return 0; +} + +static const struct rtc_class_ops m48t86_rtc_ops = { + .read_time = m48t86_rtc_read_time, + .set_time = m48t86_rtc_set_time, + .proc = m48t86_rtc_proc, +}; + +static int m48t86_nvram_read(void *priv, unsigned int off, void *buf, + size_t count) +{ + struct device *dev = priv; + unsigned int i; + + for (i = 0; i < count; i++) + ((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i)); + + return 0; +} + +static int m48t86_nvram_write(void *priv, unsigned int off, void *buf, + size_t count) +{ + struct device *dev = priv; + unsigned int i; + + for (i = 0; i < count; i++) + m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i)); + + return 0; +} + +/* + * The RTC is an optional feature at purchase time on some Technologic Systems + * boards. Verify that it actually exists by checking if the last two bytes + * of the NVRAM can be changed. + * + * This is based on the method used in their rtc7800.c example. + */ +static bool m48t86_verify_chip(struct platform_device *pdev) +{ + unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2); + unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1); + unsigned char tmp0, tmp1; + + tmp0 = m48t86_readb(&pdev->dev, offset0); + tmp1 = m48t86_readb(&pdev->dev, offset1); + + m48t86_writeb(&pdev->dev, 0x00, offset0); + m48t86_writeb(&pdev->dev, 0x55, offset1); + if (m48t86_readb(&pdev->dev, offset1) == 0x55) { + m48t86_writeb(&pdev->dev, 0xaa, offset1); + if (m48t86_readb(&pdev->dev, offset1) == 0xaa && + m48t86_readb(&pdev->dev, offset0) == 0x00) { + m48t86_writeb(&pdev->dev, tmp0, offset0); + m48t86_writeb(&pdev->dev, tmp1, offset1); + + return true; + } + } + return false; +} + +static int m48t86_rtc_probe(struct platform_device *pdev) +{ + struct m48t86_rtc_info *info; + struct rtc_device *rtc; + unsigned char reg; + int err; + struct nvmem_config m48t86_nvmem_cfg = { + .name = "m48t86_nvram", + .word_size = 1, + .stride = 1, + .size = M48T86_NVRAM_LEN, + .reg_read = m48t86_nvram_read, + .reg_write = m48t86_nvram_write, + .priv = &pdev->dev, + }; + + info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL); + if (!info) + return -ENOMEM; + + info->index_reg = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(info->index_reg)) + return PTR_ERR(info->index_reg); + + info->data_reg = devm_platform_ioremap_resource(pdev, 1); + if (IS_ERR(info->data_reg)) + return PTR_ERR(info->data_reg); + + dev_set_drvdata(&pdev->dev, info); + + if (!m48t86_verify_chip(pdev)) { + dev_info(&pdev->dev, "RTC not present\n"); + return -ENODEV; + } + + rtc = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + rtc->ops = &m48t86_rtc_ops; + + err = devm_rtc_register_device(rtc); + if (err) + return err; + + devm_rtc_nvmem_register(rtc, &m48t86_nvmem_cfg); + + /* read battery status */ + reg = m48t86_readb(&pdev->dev, M48T86_D); + dev_info(&pdev->dev, "battery %s\n", + (reg & M48T86_D_VRT) ? "ok" : "exhausted"); + + return 0; +} + +static const struct of_device_id m48t86_rtc_of_ids[] = { + { .compatible = "st,m48t86" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, m48t86_rtc_of_ids); + +static struct platform_driver m48t86_rtc_platform_driver = { + .driver = { + .name = "rtc-m48t86", + .of_match_table = m48t86_rtc_of_ids, + }, + .probe = m48t86_rtc_probe, +}; + +module_platform_driver(m48t86_rtc_platform_driver); + +MODULE_AUTHOR("Alessandro Zummo "); +MODULE_DESCRIPTION("M48T86 RTC driver"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:rtc-m48t86"); -- cgit v1.3.1