Merge tag 'armsoc-dt64' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc
[linux-2.6-block.git] / drivers / clocksource / armv7m_systick.c
1 /*
2  * Copyright (C) Maxime Coquelin 2015
3  * Author:  Maxime Coquelin <mcoquelin.stm32@gmail.com>
4  * License terms:  GNU General Public License (GPL), version 2
5  */
6
7 #include <linux/kernel.h>
8 #include <linux/clocksource.h>
9 #include <linux/clockchips.h>
10 #include <linux/io.h>
11 #include <linux/of.h>
12 #include <linux/of_address.h>
13 #include <linux/clk.h>
14 #include <linux/bitops.h>
15
16 #define SYST_CSR        0x00
17 #define SYST_RVR        0x04
18 #define SYST_CVR        0x08
19 #define SYST_CALIB      0x0c
20
21 #define SYST_CSR_ENABLE BIT(0)
22
23 #define SYSTICK_LOAD_RELOAD_MASK 0x00FFFFFF
24
25 static int __init system_timer_of_register(struct device_node *np)
26 {
27         struct clk *clk = NULL;
28         void __iomem *base;
29         u32 rate;
30         int ret;
31
32         base = of_iomap(np, 0);
33         if (!base) {
34                 pr_warn("system-timer: invalid base address\n");
35                 return -ENXIO;
36         }
37
38         ret = of_property_read_u32(np, "clock-frequency", &rate);
39         if (ret) {
40                 clk = of_clk_get(np, 0);
41                 if (IS_ERR(clk)) {
42                         ret = PTR_ERR(clk);
43                         goto out_unmap;
44                 }
45
46                 ret = clk_prepare_enable(clk);
47                 if (ret)
48                         goto out_clk_put;
49
50                 rate = clk_get_rate(clk);
51                 if (!rate) {
52                         ret = -EINVAL;
53                         goto out_clk_disable;
54                 }
55         }
56
57         writel_relaxed(SYSTICK_LOAD_RELOAD_MASK, base + SYST_RVR);
58         writel_relaxed(SYST_CSR_ENABLE, base + SYST_CSR);
59
60         ret = clocksource_mmio_init(base + SYST_CVR, "arm_system_timer", rate,
61                         200, 24, clocksource_mmio_readl_down);
62         if (ret) {
63                 pr_err("failed to init clocksource (%d)\n", ret);
64                 if (clk)
65                         goto out_clk_disable;
66                 else
67                         goto out_unmap;
68         }
69
70         pr_info("ARM System timer initialized as clocksource\n");
71
72         return 0;
73
74 out_clk_disable:
75         clk_disable_unprepare(clk);
76 out_clk_put:
77         clk_put(clk);
78 out_unmap:
79         iounmap(base);
80         pr_warn("ARM System timer register failed (%d)\n", ret);
81
82         return ret;
83 }
84
85 CLOCKSOURCE_OF_DECLARE(arm_systick, "arm,armv7m-systick",
86                         system_timer_of_register);