From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- drivers/rtc/rtc-ds2404.c | 225 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 225 insertions(+) create mode 100644 drivers/rtc/rtc-ds2404.c (limited to 'drivers/rtc/rtc-ds2404.c') diff --git a/drivers/rtc/rtc-ds2404.c b/drivers/rtc/rtc-ds2404.c new file mode 100644 index 000000000..217694eca --- /dev/null +++ b/drivers/rtc/rtc-ds2404.c @@ -0,0 +1,225 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2012 Sven Schnelle + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#define DS2404_STATUS_REG 0x200 +#define DS2404_CONTROL_REG 0x201 +#define DS2404_RTC_REG 0x202 + +#define DS2404_WRITE_SCRATCHPAD_CMD 0x0f +#define DS2404_READ_SCRATCHPAD_CMD 0xaa +#define DS2404_COPY_SCRATCHPAD_CMD 0x55 +#define DS2404_READ_MEMORY_CMD 0xf0 + +#define DS2404_RST 0 +#define DS2404_CLK 1 +#define DS2404_DQ 2 + +struct ds2404 { + struct device *dev; + struct gpio_desc *rst_gpiod; + struct gpio_desc *clk_gpiod; + struct gpio_desc *dq_gpiod; +}; + +static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + + /* This will de-assert RESET, declare this GPIO as GPIOD_ACTIVE_LOW */ + chip->rst_gpiod = devm_gpiod_get(dev, "rst", GPIOD_OUT_LOW); + if (IS_ERR(chip->rst_gpiod)) + return PTR_ERR(chip->rst_gpiod); + + chip->clk_gpiod = devm_gpiod_get(dev, "clk", GPIOD_OUT_HIGH); + if (IS_ERR(chip->clk_gpiod)) + return PTR_ERR(chip->clk_gpiod); + + chip->dq_gpiod = devm_gpiod_get(dev, "dq", GPIOD_ASIS); + if (IS_ERR(chip->dq_gpiod)) + return PTR_ERR(chip->dq_gpiod); + + return 0; +} + +static void ds2404_reset(struct ds2404 *chip) +{ + gpiod_set_value(chip->rst_gpiod, 1); + udelay(1000); + gpiod_set_value(chip->rst_gpiod, 0); + gpiod_set_value(chip->clk_gpiod, 0); + gpiod_direction_output(chip->dq_gpiod, 0); + udelay(10); +} + +static void ds2404_write_byte(struct ds2404 *chip, u8 byte) +{ + int i; + + gpiod_direction_output(chip->dq_gpiod, 1); + for (i = 0; i < 8; i++) { + gpiod_set_value(chip->dq_gpiod, byte & (1 << i)); + udelay(10); + gpiod_set_value(chip->clk_gpiod, 1); + udelay(10); + gpiod_set_value(chip->clk_gpiod, 0); + udelay(10); + } +} + +static u8 ds2404_read_byte(struct ds2404 *chip) +{ + int i; + u8 ret = 0; + + gpiod_direction_input(chip->dq_gpiod); + + for (i = 0; i < 8; i++) { + gpiod_set_value(chip->clk_gpiod, 0); + udelay(10); + if (gpiod_get_value(chip->dq_gpiod)) + ret |= 1 << i; + gpiod_set_value(chip->clk_gpiod, 1); + udelay(10); + } + return ret; +} + +static void ds2404_read_memory(struct ds2404 *chip, u16 offset, + int length, u8 *out) +{ + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_READ_MEMORY_CMD); + ds2404_write_byte(chip, offset & 0xff); + ds2404_write_byte(chip, (offset >> 8) & 0xff); + while (length--) + *out++ = ds2404_read_byte(chip); +} + +static void ds2404_write_memory(struct ds2404 *chip, u16 offset, + int length, u8 *out) +{ + int i; + u8 ta01, ta02, es; + + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_WRITE_SCRATCHPAD_CMD); + ds2404_write_byte(chip, offset & 0xff); + ds2404_write_byte(chip, (offset >> 8) & 0xff); + + for (i = 0; i < length; i++) + ds2404_write_byte(chip, out[i]); + + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_READ_SCRATCHPAD_CMD); + + ta01 = ds2404_read_byte(chip); + ta02 = ds2404_read_byte(chip); + es = ds2404_read_byte(chip); + + for (i = 0; i < length; i++) { + if (out[i] != ds2404_read_byte(chip)) { + dev_err(chip->dev, "read invalid data\n"); + return; + } + } + + ds2404_reset(chip); + ds2404_write_byte(chip, DS2404_COPY_SCRATCHPAD_CMD); + ds2404_write_byte(chip, ta01); + ds2404_write_byte(chip, ta02); + ds2404_write_byte(chip, es); + + while (gpiod_get_value(chip->dq_gpiod)) + ; +} + +static void ds2404_enable_osc(struct ds2404 *chip) +{ + u8 in[1] = { 0x10 }; /* enable oscillator */ + + ds2404_write_memory(chip, 0x201, 1, in); +} + +static int ds2404_read_time(struct device *dev, struct rtc_time *dt) +{ + struct ds2404 *chip = dev_get_drvdata(dev); + unsigned long time = 0; + __le32 hw_time = 0; + + ds2404_read_memory(chip, 0x203, 4, (u8 *)&hw_time); + time = le32_to_cpu(hw_time); + + rtc_time64_to_tm(time, dt); + return 0; +} + +static int ds2404_set_time(struct device *dev, struct rtc_time *dt) +{ + struct ds2404 *chip = dev_get_drvdata(dev); + u32 time = cpu_to_le32(rtc_tm_to_time64(dt)); + ds2404_write_memory(chip, 0x203, 4, (u8 *)&time); + return 0; +} + +static const struct rtc_class_ops ds2404_rtc_ops = { + .read_time = ds2404_read_time, + .set_time = ds2404_set_time, +}; + +static int rtc_probe(struct platform_device *pdev) +{ + struct ds2404 *chip; + struct rtc_device *rtc; + int retval = -EBUSY; + + chip = devm_kzalloc(&pdev->dev, sizeof(struct ds2404), GFP_KERNEL); + if (!chip) + return -ENOMEM; + + chip->dev = &pdev->dev; + + rtc = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + retval = ds2404_gpio_map(chip, pdev); + if (retval) + return retval; + + platform_set_drvdata(pdev, chip); + + rtc->ops = &ds2404_rtc_ops; + rtc->range_max = U32_MAX; + + retval = devm_rtc_register_device(rtc); + if (retval) + return retval; + + ds2404_enable_osc(chip); + return 0; +} + +static struct platform_driver rtc_device_driver = { + .probe = rtc_probe, + .driver = { + .name = "ds2404", + }, +}; +module_platform_driver(rtc_device_driver); + +MODULE_DESCRIPTION("DS2404 RTC"); +MODULE_AUTHOR("Sven Schnelle"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:ds2404"); -- cgit v1.3.1