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// SPDX-License-Identifier: GPL-2.0-only OR MIT
/*
* Apple SMC RTC driver
* Copyright The Asahi Linux Contributors
*/
#include <linux/bitops.h>
#include <linux/mfd/macsmc.h>
#include <linux/module.h>
#include <linux/nvmem-consumer.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/slab.h>
/* 48-bit RTC */
#define RTC_BYTES 6
#define RTC_BITS (8 * RTC_BYTES)
/* 32768 Hz clock */
#define RTC_SEC_SHIFT 15
struct macsmc_rtc {
struct device *dev;
struct apple_smc *smc;
struct rtc_device *rtc_dev;
struct nvmem_cell *rtc_offset;
};
static int macsmc_rtc_get_time(struct device *dev, struct rtc_time *tm)
{
struct macsmc_rtc *rtc = dev_get_drvdata(dev);
u64 ctr = 0, off = 0;
time64_t now;
void *p_off;
size_t len;
int ret;
ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES);
if (ret < 0)
return ret;
if (ret != RTC_BYTES)
return -EIO;
p_off = nvmem_cell_read(rtc->rtc_offset, &len);
if (IS_ERR(p_off))
return PTR_ERR(p_off);
if (len < RTC_BYTES) {
kfree(p_off);
return -EIO;
}
memcpy(&off, p_off, RTC_BYTES);
kfree(p_off);
/* Sign extend from 48 to 64 bits, then arithmetic shift right 15 bits to get seconds */
now = sign_extend64(ctr + off, RTC_BITS - 1) >> RTC_SEC_SHIFT;
rtc_time64_to_tm(now, tm);
return ret;
}
static int macsmc_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct macsmc_rtc *rtc = dev_get_drvdata(dev);
u64 ctr = 0, off = 0;
int ret;
ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES);
if (ret < 0)
return ret;
if (ret != RTC_BYTES)
return -EIO;
/* This sets the offset such that the set second begins now */
off = (rtc_tm_to_time64(tm) << RTC_SEC_SHIFT) - ctr;
return nvmem_cell_write(rtc->rtc_offset, &off, RTC_BYTES);
}
static const struct rtc_class_ops macsmc_rtc_ops = {
.read_time = macsmc_rtc_get_time,
.set_time = macsmc_rtc_set_time,
};
static int macsmc_rtc_probe(struct platform_device *pdev)
{
struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
struct macsmc_rtc *rtc;
/*
* MFD will probe this device even without a node in the device tree,
* thus bail out early if the SMC on the current machines does not
* support RTC and has no node in the device tree.
*/
if (!pdev->dev.of_node)
return -ENODEV;
rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
if (!rtc)
return -ENOMEM;
rtc->dev = &pdev->dev;
rtc->smc = smc;
rtc->rtc_offset = devm_nvmem_cell_get(&pdev->dev, "rtc_offset");
if (IS_ERR(rtc->rtc_offset))
return dev_err_probe(&pdev->dev, PTR_ERR(rtc->rtc_offset),
"Failed to get rtc_offset NVMEM cell\n");
rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(rtc->rtc_dev))
return PTR_ERR(rtc->rtc_dev);
rtc->rtc_dev->ops = &macsmc_rtc_ops;
rtc->rtc_dev->range_min = S64_MIN >> (RTC_SEC_SHIFT + (64 - RTC_BITS));
rtc->rtc_dev->range_max = S64_MAX >> (RTC_SEC_SHIFT + (64 - RTC_BITS));
platform_set_drvdata(pdev, rtc);
return devm_rtc_register_device(rtc->rtc_dev);
}
static const struct of_device_id macsmc_rtc_of_table[] = {
{ .compatible = "apple,smc-rtc", },
{}
};
MODULE_DEVICE_TABLE(of, macsmc_rtc_of_table);
static struct platform_driver macsmc_rtc_driver = {
.driver = {
.name = "macsmc-rtc",
.of_match_table = macsmc_rtc_of_table,
},
.probe = macsmc_rtc_probe,
};
module_platform_driver(macsmc_rtc_driver);
MODULE_LICENSE("Dual MIT/GPL");
MODULE_DESCRIPTION("Apple SMC RTC driver");
MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
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