drivers/watchdog/rzn1_wdt.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Renesas RZ/N1 Watchdog timer.
   4  * This is a 12-bit timer driver from a (62.5/16384) MHz clock. It can't even
   5  * cope with 2 seconds.
   6  *
   7  * Copyright 2018 Renesas Electronics Europe Ltd.
   8  *
   9  * Derived from Ralink RT288x watchdog timer.
  10  */
  11
  12 #include <linux/clk.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/of_address.h>
  17 #include <linux/of_irq.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/reboot.h>
  20 #include <linux/watchdog.h>
  21
  22 #define DEFAULT_TIMEOUT         60
  23
  24 #define RZN1_WDT_RETRIGGER                      0x0
  25 #define RZN1_WDT_RETRIGGER_RELOAD_VAL           0
  26 #define RZN1_WDT_RETRIGGER_RELOAD_VAL_MASK      0xfff
  27 #define RZN1_WDT_RETRIGGER_PRESCALE             BIT(12)
  28 #define RZN1_WDT_RETRIGGER_ENABLE               BIT(13)
  29 #define RZN1_WDT_RETRIGGER_WDSI                 (0x2 << 14)
  30
  31 #define RZN1_WDT_PRESCALER                      16384
  32 #define RZN1_WDT_MAX                            4095
  33
  34 struct rzn1_watchdog {
  35         struct watchdog_device          wdtdev;
  36         void __iomem                    *base;
  37         unsigned long                   clk_rate_khz;
  38 };
  39
  40 static inline uint32_t max_heart_beat_ms(unsigned long clk_rate_khz)
  41 {
  42         return (RZN1_WDT_MAX * RZN1_WDT_PRESCALER) / clk_rate_khz;
  43 }
  44
  45 static inline uint32_t compute_reload_value(uint32_t tick_ms,
  46                                             unsigned long clk_rate_khz)
  47 {
  48         return (tick_ms * clk_rate_khz) / RZN1_WDT_PRESCALER;
  49 }
  50
  51 static int rzn1_wdt_ping(struct watchdog_device *w)
  52 {
  53         struct rzn1_watchdog *wdt = watchdog_get_drvdata(w);
  54
  55         /* Any value retrigggers the watchdog */
  56         writel(0, wdt->base + RZN1_WDT_RETRIGGER);
  57
  58         return 0;
  59 }
  60
  61 static int rzn1_wdt_start(struct watchdog_device *w)
  62 {
  63         struct rzn1_watchdog *wdt = watchdog_get_drvdata(w);
  64         u32 val;
  65
  66         /*
  67          * The hardware allows you to write to this reg only once.
  68          * Since this includes the reload value, there is no way to change the
  69          * timeout once started. Also note that the WDT clock is half the bus
  70          * fabric clock rate, so if the bus fabric clock rate is changed after
  71          * the WDT is started, the WDT interval will be wrong.
  72          */
  73         val = RZN1_WDT_RETRIGGER_WDSI;
  74         val |= RZN1_WDT_RETRIGGER_ENABLE;
  75         val |= RZN1_WDT_RETRIGGER_PRESCALE;
  76         val |= compute_reload_value(w->max_hw_heartbeat_ms, wdt->clk_rate_khz);
  77         writel(val, wdt->base + RZN1_WDT_RETRIGGER);
  78
  79         return 0;
  80 }
  81
  82 static irqreturn_t rzn1_wdt_irq(int irq, void *_wdt)
  83 {
  84         pr_crit("RZN1 Watchdog. Initiating system reboot\n");
  85         emergency_restart();
  86
  87         return IRQ_HANDLED;
  88 }
  89
  90 static struct watchdog_info rzn1_wdt_info = {
  91         .identity = "RZ/N1 Watchdog",
  92         .options = WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
  93 };
  94
  95 static const struct watchdog_ops rzn1_wdt_ops = {
  96         .owner = THIS_MODULE,
  97         .start = rzn1_wdt_start,
  98         .ping = rzn1_wdt_ping,
  99 };
 100
 101 static int rzn1_wdt_probe(struct platform_device *pdev)
 102 {
 103         struct device *dev = &pdev->dev;
 104         struct rzn1_watchdog *wdt;
 105         struct device_node *np = dev->of_node;
 106         struct clk *clk;
 107         unsigned long clk_rate;
 108         int ret;
 109         int irq;
 110
 111         wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
 112         if (!wdt)
 113                 return -ENOMEM;
 114
 115         wdt->base = devm_platform_ioremap_resource(pdev, 0);
 116         if (IS_ERR(wdt->base))
 117                 return PTR_ERR(wdt->base);
 118
 119         irq = platform_get_irq(pdev, 0);
 120         if (irq < 0)
 121                 return irq;
 122
 123         ret = devm_request_irq(dev, irq, rzn1_wdt_irq, 0,
 124                                np->name, wdt);
 125         if (ret) {
 126                 dev_err(dev, "failed to request irq %d\n", irq);
 127                 return ret;
 128         }
 129
 130         clk = devm_clk_get_enabled(dev, NULL);
 131         if (IS_ERR(clk)) {
 132                 dev_err(dev, "failed to get the clock\n");
 133                 return PTR_ERR(clk);
 134         }
 135
 136         clk_rate = clk_get_rate(clk);
 137         if (!clk_rate) {
 138                 dev_err(dev, "failed to get the clock rate\n");
 139                 return -EINVAL;
 140         }
 141
 142         wdt->clk_rate_khz = clk_rate / 1000;
 143         wdt->wdtdev.info = &rzn1_wdt_info;
 144         wdt->wdtdev.ops = &rzn1_wdt_ops;
 145         wdt->wdtdev.status = WATCHDOG_NOWAYOUT_INIT_STATUS;
 146         wdt->wdtdev.parent = dev;
 147         /*
 148          * The period of the watchdog cannot be changed once set
 149          * and is limited to a very short period.
 150          * Configure it for a 1s period once and for all, and
 151          * rely on the heart-beat provided by the watchdog core
 152          * to make this usable by the user-space.
 153          */
 154         wdt->wdtdev.max_hw_heartbeat_ms = max_heart_beat_ms(wdt->clk_rate_khz);
 155         if (wdt->wdtdev.max_hw_heartbeat_ms > 1000)
 156                 wdt->wdtdev.max_hw_heartbeat_ms = 1000;
 157
 158         wdt->wdtdev.timeout = DEFAULT_TIMEOUT;
 159         ret = watchdog_init_timeout(&wdt->wdtdev, 0, dev);
 160         if (ret)
 161                 return ret;
 162
 163         watchdog_set_drvdata(&wdt->wdtdev, wdt);
 164
 165         return devm_watchdog_register_device(dev, &wdt->wdtdev);
 166 }
 167
 168
 169 static const struct of_device_id rzn1_wdt_match[] = {
 170         { .compatible = "renesas,rzn1-wdt" },
 171         {},
 172 };
 173 MODULE_DEVICE_TABLE(of, rzn1_wdt_match);
 174
 175 static struct platform_driver rzn1_wdt_driver = {
 176         .probe          = rzn1_wdt_probe,
 177         .driver         = {
 178                 .name           = KBUILD_MODNAME,
 179                 .of_match_table = rzn1_wdt_match,
 180         },
 181 };
 182
 183 module_platform_driver(rzn1_wdt_driver);
 184
 185 MODULE_DESCRIPTION("Renesas RZ/N1 hardware watchdog");
 186 MODULE_AUTHOR("Phil Edworthy <phil.edworthy@renesas.com>");
 187 MODULE_LICENSE("GPL");