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140 lines · 3.4 KiB

1// SPDX-License-Identifier: GPL-2.0-only OR MIT
2/*
3 * Apple SMC RTC driver
4 * Copyright The Asahi Linux Contributors
5 */
6
7#include <linux/bitops.h>
8#include <linux/mfd/macsmc.h>
9#include <linux/module.h>
10#include <linux/nvmem-consumer.h>
11#include <linux/of.h>
12#include <linux/platform_device.h>
13#include <linux/rtc.h>
14#include <linux/slab.h>
15
16/* 48-bit RTC */
17#define RTC_BYTES 6
18#define RTC_BITS (8 * RTC_BYTES)
19
20/* 32768 Hz clock */
21#define RTC_SEC_SHIFT 15
22
23struct macsmc_rtc {
24 struct device *dev;
25 struct apple_smc *smc;
26 struct rtc_device *rtc_dev;
27 struct nvmem_cell *rtc_offset;
28};
29
30static int macsmc_rtc_get_time(struct device *dev, struct rtc_time *tm)
31{
32 struct macsmc_rtc *rtc = dev_get_drvdata(dev);
33 u64 ctr = 0, off = 0;
34 time64_t now;
35 void *p_off;
36 size_t len;
37 int ret;
38
39 ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES);
40 if (ret < 0)
41 return ret;
42 if (ret != RTC_BYTES)
43 return -EIO;
44
45 p_off = nvmem_cell_read(rtc->rtc_offset, &len);
46 if (IS_ERR(p_off))
47 return PTR_ERR(p_off);
48 if (len < RTC_BYTES) {
49 kfree(p_off);
50 return -EIO;
51 }
52
53 memcpy(&off, p_off, RTC_BYTES);
54 kfree(p_off);
55
56 /* Sign extend from 48 to 64 bits, then arithmetic shift right 15 bits to get seconds */
57 now = sign_extend64(ctr + off, RTC_BITS - 1) >> RTC_SEC_SHIFT;
58 rtc_time64_to_tm(now, tm);
59
60 return ret;
61}
62
63static int macsmc_rtc_set_time(struct device *dev, struct rtc_time *tm)
64{
65 struct macsmc_rtc *rtc = dev_get_drvdata(dev);
66 u64 ctr = 0, off = 0;
67 int ret;
68
69 ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES);
70 if (ret < 0)
71 return ret;
72 if (ret != RTC_BYTES)
73 return -EIO;
74
75 /* This sets the offset such that the set second begins now */
76 off = (rtc_tm_to_time64(tm) << RTC_SEC_SHIFT) - ctr;
77 return nvmem_cell_write(rtc->rtc_offset, &off, RTC_BYTES);
78}
79
80static const struct rtc_class_ops macsmc_rtc_ops = {
81 .read_time = macsmc_rtc_get_time,
82 .set_time = macsmc_rtc_set_time,
83};
84
85static int macsmc_rtc_probe(struct platform_device *pdev)
86{
87 struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
88 struct macsmc_rtc *rtc;
89
90 /*
91 * MFD will probe this device even without a node in the device tree,
92 * thus bail out early if the SMC on the current machines does not
93 * support RTC and has no node in the device tree.
94 */
95 if (!pdev->dev.of_node)
96 return -ENODEV;
97
98 rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
99 if (!rtc)
100 return -ENOMEM;
101
102 rtc->dev = &pdev->dev;
103 rtc->smc = smc;
104
105 rtc->rtc_offset = devm_nvmem_cell_get(&pdev->dev, "rtc_offset");
106 if (IS_ERR(rtc->rtc_offset))
107 return dev_err_probe(&pdev->dev, PTR_ERR(rtc->rtc_offset),
108 "Failed to get rtc_offset NVMEM cell\n");
109
110 rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
111 if (IS_ERR(rtc->rtc_dev))
112 return PTR_ERR(rtc->rtc_dev);
113
114 rtc->rtc_dev->ops = &macsmc_rtc_ops;
115 rtc->rtc_dev->range_min = S64_MIN >> (RTC_SEC_SHIFT + (64 - RTC_BITS));
116 rtc->rtc_dev->range_max = S64_MAX >> (RTC_SEC_SHIFT + (64 - RTC_BITS));
117
118 platform_set_drvdata(pdev, rtc);
119
120 return devm_rtc_register_device(rtc->rtc_dev);
121}
122
123static const struct of_device_id macsmc_rtc_of_table[] = {
124 { .compatible = "apple,smc-rtc", },
125 {}
126};
127MODULE_DEVICE_TABLE(of, macsmc_rtc_of_table);
128
129static struct platform_driver macsmc_rtc_driver = {
130 .driver = {
131 .name = "macsmc-rtc",
132 .of_match_table = macsmc_rtc_of_table,
133 },
134 .probe = macsmc_rtc_probe,
135};
136module_platform_driver(macsmc_rtc_driver);
137
138MODULE_LICENSE("Dual MIT/GPL");
139MODULE_DESCRIPTION("Apple SMC RTC driver");
140MODULE_AUTHOR("Hector Martin <[email protected]>");