diff options
Diffstat (limited to 'drivers/rtc/rtc-macsmc.c')
| -rw-r--r-- | drivers/rtc/rtc-macsmc.c | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-macsmc.c b/drivers/rtc/rtc-macsmc.c new file mode 100644 index 000000000000..34730c925248 --- /dev/null +++ b/drivers/rtc/rtc-macsmc.c @@ -0,0 +1,130 @@ +// 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/core.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 != RTC_BYTES) + return ret < 0 ? ret : -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 != RTC_BYTES) + return ret < 0 ? ret : -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; + + /* Ignore devices without this functionality */ + if (!apple_smc_key_exists(smc, SMC_KEY(CLKM))) + return -ENODEV; + + rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL); + if (!rtc) + return -ENOMEM; + + rtc->dev = &pdev->dev; + rtc->smc = smc; + + pdev->dev.of_node = of_get_child_by_name(pdev->dev.parent->of_node, "rtc"); + + 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 struct platform_driver macsmc_rtc_driver = { + .driver = { + .name = "macsmc-rtc", + .owner = THIS_MODULE, + }, + .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>"); +MODULE_ALIAS("platform:macsmc-rtc"); |