drivers/watchdog/renesas_wdt.c

   1 /*
   2  * Watchdog driver for Renesas WDT watchdog
   3  *
   4  * Copyright (C) 2015-16 Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
   5  * Copyright (C) 2015-16 Renesas Electronics Corporation
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published by
   9  * the Free Software Foundation.
  10  */
  11 #include <linux/bitops.h>
  12 #include <linux/clk.h>
  13 #include <linux/io.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/of.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/pm_runtime.h>
  19 #include <linux/watchdog.h>
  20
  21 #define RWTCNT          0
  22 #define RWTCSRA         4
  23 #define RWTCSRA_WOVF    BIT(4)
  24 #define RWTCSRA_WRFLG   BIT(5)
  25 #define RWTCSRA_TME     BIT(7)
  26
  27 #define RWDT_DEFAULT_TIMEOUT 60U
  28
  29 static const unsigned int clk_divs[] = { 1, 4, 16, 32, 64, 128, 1024 };
  30
  31 static bool nowayout = WATCHDOG_NOWAYOUT;
  32 module_param(nowayout, bool, 0);
  33 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  34                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  35
  36 struct rwdt_priv {
  37         void __iomem *base;
  38         struct watchdog_device wdev;
  39         struct clk *clk;
  40         unsigned int clks_per_sec;
  41         u8 cks;
  42 };
  43
  44 static void rwdt_write(struct rwdt_priv *priv, u32 val, unsigned int reg)
  45 {
  46         if (reg == RWTCNT)
  47                 val |= 0x5a5a0000;
  48         else
  49                 val |= 0xa5a5a500;
  50
  51         writel_relaxed(val, priv->base + reg);
  52 }
  53
  54 static int rwdt_init_timeout(struct watchdog_device *wdev)
  55 {
  56         struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
  57
  58         rwdt_write(priv, 65536 - wdev->timeout * priv->clks_per_sec, RWTCNT);
  59
  60         return 0;
  61 }
  62
  63 static int rwdt_start(struct watchdog_device *wdev)
  64 {
  65         struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
  66
  67         clk_prepare_enable(priv->clk);
  68
  69         rwdt_write(priv, priv->cks, RWTCSRA);
  70         rwdt_init_timeout(wdev);
  71
  72         while (readb_relaxed(priv->base + RWTCSRA) & RWTCSRA_WRFLG)
  73                 cpu_relax();
  74
  75         rwdt_write(priv, priv->cks | RWTCSRA_TME, RWTCSRA);
  76
  77         return 0;
  78 }
  79
  80 static int rwdt_stop(struct watchdog_device *wdev)
  81 {
  82         struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
  83
  84         rwdt_write(priv, priv->cks, RWTCSRA);
  85         clk_disable_unprepare(priv->clk);
  86
  87         return 0;
  88 }
  89
  90 static unsigned int rwdt_get_timeleft(struct watchdog_device *wdev)
  91 {
  92         struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
  93         u16 val = readw_relaxed(priv->base + RWTCNT);
  94
  95         return DIV_ROUND_CLOSEST(65536 - val, priv->clks_per_sec);
  96 }
  97
  98 static const struct watchdog_info rwdt_ident = {
  99         .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
 100         .identity = "Renesas WDT Watchdog",
 101 };
 102
 103 static const struct watchdog_ops rwdt_ops = {
 104         .owner = THIS_MODULE,
 105         .start = rwdt_start,
 106         .stop = rwdt_stop,
 107         .ping = rwdt_init_timeout,
 108         .get_timeleft = rwdt_get_timeleft,
 109 };
 110
 111 static int rwdt_probe(struct platform_device *pdev)
 112 {
 113         struct rwdt_priv *priv;
 114         struct resource *res;
 115         unsigned long rate;
 116         unsigned int clks_per_sec;
 117         int ret, i;
 118
 119         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 120         if (!priv)
 121                 return -ENOMEM;
 122
 123         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 124         priv->base = devm_ioremap_resource(&pdev->dev, res);
 125         if (IS_ERR(priv->base))
 126                 return PTR_ERR(priv->base);
 127
 128         priv->clk = devm_clk_get(&pdev->dev, NULL);
 129         if (IS_ERR(priv->clk))
 130                 return PTR_ERR(priv->clk);
 131
 132         rate = clk_get_rate(priv->clk);
 133         if (!rate)
 134                 return -ENOENT;
 135
 136         for (i = ARRAY_SIZE(clk_divs) - 1; i >= 0; i--) {
 137                 clks_per_sec = DIV_ROUND_UP(rate, clk_divs[i]);
 138                 if (clks_per_sec) {
 139                         priv->clks_per_sec = clks_per_sec;
 140                         priv->cks = i;
 141                         break;
 142                 }
 143         }
 144
 145         if (!clks_per_sec) {
 146                 dev_err(&pdev->dev, "Can't find suitable clock divider\n");
 147                 return -ERANGE;
 148         }
 149
 150         pm_runtime_enable(&pdev->dev);
 151         pm_runtime_get_sync(&pdev->dev);
 152
 153         priv->wdev.info = &rwdt_ident,
 154         priv->wdev.ops = &rwdt_ops,
 155         priv->wdev.parent = &pdev->dev;
 156         priv->wdev.min_timeout = 1;
 157         priv->wdev.max_timeout = 65536 / clks_per_sec;
 158         priv->wdev.timeout = min(priv->wdev.max_timeout, RWDT_DEFAULT_TIMEOUT);
 159
 160         platform_set_drvdata(pdev, priv);
 161         watchdog_set_drvdata(&priv->wdev, priv);
 162         watchdog_set_nowayout(&priv->wdev, nowayout);
 163
 164         /* This overrides the default timeout only if DT configuration was found */
 165         ret = watchdog_init_timeout(&priv->wdev, 0, &pdev->dev);
 166         if (ret)
 167                 dev_warn(&pdev->dev, "Specified timeout value invalid, using default\n");
 168
 169         ret = watchdog_register_device(&priv->wdev);
 170         if (ret < 0) {
 171                 pm_runtime_put(&pdev->dev);
 172                 pm_runtime_disable(&pdev->dev);
 173                 return ret;
 174         }
 175
 176         return 0;
 177 }
 178
 179 static int rwdt_remove(struct platform_device *pdev)
 180 {
 181         struct rwdt_priv *priv = platform_get_drvdata(pdev);
 182
 183         watchdog_unregister_device(&priv->wdev);
 184         pm_runtime_put(&pdev->dev);
 185         pm_runtime_disable(&pdev->dev);
 186
 187         return 0;
 188 }
 189
 190 /*
 191  * This driver does also fit for R-Car Gen2 (r8a779[0-4]) WDT. However, for SMP
 192  * to work there, one also needs a RESET (RST) driver which does not exist yet
 193  * due to HW issues. This needs to be solved before adding compatibles here.
 194  */
 195 static const struct of_device_id rwdt_ids[] = {
 196         { .compatible = "renesas,rcar-gen3-wdt", },
 197         { /* sentinel */ }
 198 };
 199 MODULE_DEVICE_TABLE(of, rwdt_ids);
 200
 201 static struct platform_driver rwdt_driver = {
 202         .driver = {
 203                 .name = "renesas_wdt",
 204                 .of_match_table = rwdt_ids,
 205         },
 206         .probe = rwdt_probe,
 207         .remove = rwdt_remove,
 208 };
 209 module_platform_driver(rwdt_driver);
 210
 211 MODULE_DESCRIPTION("Renesas WDT Watchdog Driver");
 212 MODULE_LICENSE("GPL v2");
 213 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");