drivers/clocksource/clksrc_st_lpc.c

   1 /*
   2  * Clocksource using the Low Power Timer found in the Low Power Controller (LPC)
   3  *
   4  * Copyright (C) 2015 STMicroelectronics – All Rights Reserved
   5  *
   6  * Author(s): Francesco Virlinzi <francesco.virlinzi@st.com>
   7  *            Ajit Pal Singh <ajitpal.singh@st.com>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  */
  14
  15 #include <linux/clk.h>
  16 #include <linux/clocksource.h>
  17 #include <linux/init.h>
  18 #include <linux/of_address.h>
  19 #include <linux/sched_clock.h>
  20 #include <linux/slab.h>
  21
  22 #include <dt-bindings/mfd/st-lpc.h>
  23
  24 /* Low Power Timer */
  25 #define LPC_LPT_LSB_OFF         0x400
  26 #define LPC_LPT_MSB_OFF         0x404
  27 #define LPC_LPT_START_OFF       0x408
  28
  29 static struct st_clksrc_ddata {
  30         struct clk              *clk;
  31         void __iomem            *base;
  32 } ddata;
  33
  34 static void __init st_clksrc_reset(void)
  35 {
  36         writel_relaxed(0, ddata.base + LPC_LPT_START_OFF);
  37         writel_relaxed(0, ddata.base + LPC_LPT_MSB_OFF);
  38         writel_relaxed(0, ddata.base + LPC_LPT_LSB_OFF);
  39         writel_relaxed(1, ddata.base + LPC_LPT_START_OFF);
  40 }
  41
  42 static u64 notrace st_clksrc_sched_clock_read(void)
  43 {
  44         return (u64)readl_relaxed(ddata.base + LPC_LPT_LSB_OFF);
  45 }
  46
  47 static int __init st_clksrc_init(void)
  48 {
  49         unsigned long rate;
  50         int ret;
  51
  52         st_clksrc_reset();
  53
  54         rate = clk_get_rate(ddata.clk);
  55
  56         sched_clock_register(st_clksrc_sched_clock_read, 32, rate);
  57
  58         ret = clocksource_mmio_init(ddata.base + LPC_LPT_LSB_OFF,
  59                                     "clksrc-st-lpc", rate, 300, 32,
  60                                     clocksource_mmio_readl_up);
  61         if (ret) {
  62                 pr_err("clksrc-st-lpc: Failed to register clocksource\n");
  63                 return ret;
  64         }
  65
  66         return 0;
  67 }
  68
  69 static int __init st_clksrc_setup_clk(struct device_node *np)
  70 {
  71         struct clk *clk;
  72
  73         clk = of_clk_get(np, 0);
  74         if (IS_ERR(clk)) {
  75                 pr_err("clksrc-st-lpc: Failed to get LPC clock\n");
  76                 return PTR_ERR(clk);
  77         }
  78
  79         if (clk_prepare_enable(clk)) {
  80                 pr_err("clksrc-st-lpc: Failed to enable LPC clock\n");
  81                 return -EINVAL;
  82         }
  83
  84         if (!clk_get_rate(clk)) {
  85                 pr_err("clksrc-st-lpc: Failed to get LPC clock rate\n");
  86                 clk_disable_unprepare(clk);
  87                 return -EINVAL;
  88         }
  89
  90         ddata.clk = clk;
  91
  92         return 0;
  93 }
  94
  95 static void __init st_clksrc_of_register(struct device_node *np)
  96 {
  97         int ret;
  98         uint32_t mode;
  99
 100         ret = of_property_read_u32(np, "st,lpc-mode", &mode);
 101         if (ret) {
 102                 pr_err("clksrc-st-lpc: An LPC mode must be provided\n");
 103                 return;
 104         }
 105
 106         /* LPC can either run as a Clocksource or in RTC or WDT mode */
 107         if (mode != ST_LPC_MODE_CLKSRC)
 108                 return;
 109
 110         ddata.base = of_iomap(np, 0);
 111         if (!ddata.base) {
 112                 pr_err("clksrc-st-lpc: Unable to map iomem\n");
 113                 return;
 114         }
 115
 116         if (st_clksrc_setup_clk(np)) {
 117                 iounmap(ddata.base);
 118                 return;
 119         }
 120
 121         if (st_clksrc_init()) {
 122                 clk_disable_unprepare(ddata.clk);
 123                 clk_put(ddata.clk);
 124                 iounmap(ddata.base);
 125                 return;
 126         }
 127
 128         pr_info("clksrc-st-lpc: clocksource initialised - running @ %luHz\n",
 129                 clk_get_rate(ddata.clk));
 130 }
 131 CLOCKSOURCE_OF_DECLARE(ddata, "st,stih407-lpc", st_clksrc_of_register);