From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- drivers/rtc/rtc-ds1302.c | 213 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 213 insertions(+) create mode 100644 drivers/rtc/rtc-ds1302.c (limited to 'drivers/rtc/rtc-ds1302.c') diff --git a/drivers/rtc/rtc-ds1302.c b/drivers/rtc/rtc-ds1302.c new file mode 100644 index 000000000..ecc7d0307 --- /dev/null +++ b/drivers/rtc/rtc-ds1302.c @@ -0,0 +1,213 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Dallas DS1302 RTC Support + * + * Copyright (C) 2002 David McCullough + * Copyright (C) 2003 - 2007 Paul Mundt + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +#define RTC_CMD_READ 0x81 /* Read command */ +#define RTC_CMD_WRITE 0x80 /* Write command */ + +#define RTC_CMD_WRITE_ENABLE 0x00 /* Write enable */ +#define RTC_CMD_WRITE_DISABLE 0x80 /* Write disable */ + +#define RTC_ADDR_RAM0 0x20 /* Address of RAM0 */ +#define RTC_ADDR_TCR 0x08 /* Address of trickle charge register */ +#define RTC_CLCK_BURST 0x1F /* Address of clock burst */ +#define RTC_CLCK_LEN 0x08 /* Size of clock burst */ +#define RTC_ADDR_CTRL 0x07 /* Address of control register */ +#define RTC_ADDR_YEAR 0x06 /* Address of year register */ +#define RTC_ADDR_DAY 0x05 /* Address of day of week register */ +#define RTC_ADDR_MON 0x04 /* Address of month register */ +#define RTC_ADDR_DATE 0x03 /* Address of day of month register */ +#define RTC_ADDR_HOUR 0x02 /* Address of hour register */ +#define RTC_ADDR_MIN 0x01 /* Address of minute register */ +#define RTC_ADDR_SEC 0x00 /* Address of second register */ + +static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time) +{ + struct spi_device *spi = dev_get_drvdata(dev); + u8 buf[1 + RTC_CLCK_LEN]; + u8 *bp; + int status; + + /* Enable writing */ + bp = buf; + *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE; + *bp++ = RTC_CMD_WRITE_ENABLE; + + status = spi_write_then_read(spi, buf, 2, + NULL, 0); + if (status) + return status; + + /* Write registers starting at the first time/date address. */ + bp = buf; + *bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE; + + *bp++ = bin2bcd(time->tm_sec); + *bp++ = bin2bcd(time->tm_min); + *bp++ = bin2bcd(time->tm_hour); + *bp++ = bin2bcd(time->tm_mday); + *bp++ = bin2bcd(time->tm_mon + 1); + *bp++ = time->tm_wday + 1; + *bp++ = bin2bcd(time->tm_year % 100); + *bp++ = RTC_CMD_WRITE_DISABLE; + + /* use write-then-read since dma from stack is nonportable */ + return spi_write_then_read(spi, buf, sizeof(buf), + NULL, 0); +} + +static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time) +{ + struct spi_device *spi = dev_get_drvdata(dev); + u8 addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ; + u8 buf[RTC_CLCK_LEN - 1]; + int status; + + /* Use write-then-read to get all the date/time registers + * since dma from stack is nonportable + */ + status = spi_write_then_read(spi, &addr, sizeof(addr), + buf, sizeof(buf)); + if (status < 0) + return status; + + /* Decode the registers */ + time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]); + time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]); + time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]); + time->tm_wday = buf[RTC_ADDR_DAY] - 1; + time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]); + time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1; + time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100; + + return 0; +} + +static const struct rtc_class_ops ds1302_rtc_ops = { + .read_time = ds1302_rtc_get_time, + .set_time = ds1302_rtc_set_time, +}; + +static int ds1302_probe(struct spi_device *spi) +{ + struct rtc_device *rtc; + u8 addr; + u8 buf[4]; + u8 *bp; + int status; + + /* Sanity check board setup data. This may be hooked up + * in 3wire mode, but we don't care. Note that unless + * there's an inverter in place, this needs SPI_CS_HIGH! + */ + if (spi->bits_per_word && (spi->bits_per_word != 8)) { + dev_err(&spi->dev, "bad word length\n"); + return -EINVAL; + } else if (spi->max_speed_hz > 2000000) { + dev_err(&spi->dev, "speed is too high\n"); + return -EINVAL; + } else if (spi->mode & SPI_CPHA) { + dev_err(&spi->dev, "bad mode\n"); + return -EINVAL; + } + + addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ; + status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1); + if (status < 0) { + dev_err(&spi->dev, "control register read error %d\n", + status); + return status; + } + + if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) { + status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1); + if (status < 0) { + dev_err(&spi->dev, "control register read error %d\n", + status); + return status; + } + + if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) { + dev_err(&spi->dev, "junk in control register\n"); + return -ENODEV; + } + } + if (buf[0] == 0) { + bp = buf; + *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE; + *bp++ = RTC_CMD_WRITE_DISABLE; + + status = spi_write_then_read(spi, buf, 2, NULL, 0); + if (status < 0) { + dev_err(&spi->dev, "control register write error %d\n", + status); + return status; + } + + addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ; + status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1); + if (status < 0) { + dev_err(&spi->dev, + "error %d reading control register\n", + status); + return status; + } + + if (buf[0] != RTC_CMD_WRITE_DISABLE) { + dev_err(&spi->dev, "failed to detect chip\n"); + return -ENODEV; + } + } + + spi_set_drvdata(spi, spi); + + rtc = devm_rtc_device_register(&spi->dev, "ds1302", + &ds1302_rtc_ops, THIS_MODULE); + if (IS_ERR(rtc)) { + status = PTR_ERR(rtc); + dev_err(&spi->dev, "error %d registering rtc\n", status); + return status; + } + + return 0; +} + +#ifdef CONFIG_OF +static const struct of_device_id ds1302_dt_ids[] = { + { .compatible = "maxim,ds1302", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, ds1302_dt_ids); +#endif + +static const struct spi_device_id ds1302_spi_ids[] = { + { .name = "ds1302", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(spi, ds1302_spi_ids); + +static struct spi_driver ds1302_driver = { + .driver.name = "rtc-ds1302", + .driver.of_match_table = of_match_ptr(ds1302_dt_ids), + .probe = ds1302_probe, + .id_table = ds1302_spi_ids, +}; + +module_spi_driver(ds1302_driver); + +MODULE_DESCRIPTION("Dallas DS1302 RTC driver"); +MODULE_AUTHOR("Paul Mundt, David McCullough"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1