drivers/watchdog/stm32_iwdg.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Driver for STM32 Independent Watchdog
   4  *
   5  * Copyright (C) STMicroelectronics 2017
   6  * Author: Yannick Fertre <yannick.fertre@st.com> for STMicroelectronics.
   7  *
   8  * This driver is based on tegra_wdt.c
   9  *
  10  */
  11
  12 #include <linux/clk.h>
  13 #include <linux/delay.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/io.h>
  16 #include <linux/iopoll.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19 #include <linux/of.h>
  20 #include <linux/platform_device.h>
  21 #include <linux/watchdog.h>
  22
  23 #define DEFAULT_TIMEOUT 10
  24
  25 /* IWDG registers */
  26 #define IWDG_KR         0x00 /* Key register */
  27 #define IWDG_PR         0x04 /* Prescaler Register */
  28 #define IWDG_RLR        0x08 /* ReLoad Register */
  29 #define IWDG_SR         0x0C /* Status Register */
  30 #define IWDG_WINR       0x10 /* Windows Register */
  31
  32 /* IWDG_KR register bit mask */
  33 #define KR_KEY_RELOAD   0xAAAA /* reload counter enable */
  34 #define KR_KEY_ENABLE   0xCCCC /* peripheral enable */
  35 #define KR_KEY_EWA      0x5555 /* write access enable */
  36 #define KR_KEY_DWA      0x0000 /* write access disable */
  37
  38 /* IWDG_PR register */
  39 #define PR_SHIFT        2
  40 #define PR_MIN          BIT(PR_SHIFT)
  41
  42 /* IWDG_RLR register values */
  43 #define RLR_MIN         0x2             /* min value recommended */
  44 #define RLR_MAX         GENMASK(11, 0)  /* max value of reload register */
  45
  46 /* IWDG_SR register bit mask */
  47 #define SR_PVU  BIT(0) /* Watchdog prescaler value update */
  48 #define SR_RVU  BIT(1) /* Watchdog counter reload value update */
  49
  50 /* set timeout to 100000 us */
  51 #define TIMEOUT_US      100000
  52 #define SLEEP_US        1000
  53
  54 struct stm32_iwdg_data {
  55         bool has_pclk;
  56         u32 max_prescaler;
  57 };
  58
  59 static const struct stm32_iwdg_data stm32_iwdg_data = {
  60         .has_pclk = false,
  61         .max_prescaler = 256,
  62 };
  63
  64 static const struct stm32_iwdg_data stm32mp1_iwdg_data = {
  65         .has_pclk = true,
  66         .max_prescaler = 1024,
  67 };
  68
  69 struct stm32_iwdg {
  70         struct watchdog_device  wdd;
  71         const struct stm32_iwdg_data *data;
  72         void __iomem            *regs;
  73         struct clk              *clk_lsi;
  74         struct clk              *clk_pclk;
  75         unsigned int            rate;
  76 };
  77
  78 static inline u32 reg_read(void __iomem *base, u32 reg)
  79 {
  80         return readl_relaxed(base + reg);
  81 }
  82
  83 static inline void reg_write(void __iomem *base, u32 reg, u32 val)
  84 {
  85         writel_relaxed(val, base + reg);
  86 }
  87
  88 static int stm32_iwdg_start(struct watchdog_device *wdd)
  89 {
  90         struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
  91         u32 tout, presc, iwdg_rlr, iwdg_pr, iwdg_sr;
  92         int ret;
  93
  94         dev_dbg(wdd->parent, "%s\n", __func__);
  95
  96         tout = clamp_t(unsigned int, wdd->timeout,
  97                        wdd->min_timeout, wdd->max_hw_heartbeat_ms / 1000);
  98
  99         presc = DIV_ROUND_UP(tout * wdt->rate, RLR_MAX + 1);
 100
 101         /* The prescaler is align on power of 2 and start at 2 ^ PR_SHIFT. */
 102         presc = roundup_pow_of_two(presc);
 103         iwdg_pr = presc <= 1 << PR_SHIFT ? 0 : ilog2(presc) - PR_SHIFT;
 104         iwdg_rlr = ((tout * wdt->rate) / presc) - 1;
 105
 106         /* enable write access */
 107         reg_write(wdt->regs, IWDG_KR, KR_KEY_EWA);
 108
 109         /* set prescaler & reload registers */
 110         reg_write(wdt->regs, IWDG_PR, iwdg_pr);
 111         reg_write(wdt->regs, IWDG_RLR, iwdg_rlr);
 112         reg_write(wdt->regs, IWDG_KR, KR_KEY_ENABLE);
 113
 114         /* wait for the registers to be updated (max 100ms) */
 115         ret = readl_relaxed_poll_timeout(wdt->regs + IWDG_SR, iwdg_sr,
 116                                          !(iwdg_sr & (SR_PVU | SR_RVU)),
 117                                          SLEEP_US, TIMEOUT_US);
 118         if (ret) {
 119                 dev_err(wdd->parent, "Fail to set prescaler, reload regs\n");
 120                 return ret;
 121         }
 122
 123         /* reload watchdog */
 124         reg_write(wdt->regs, IWDG_KR, KR_KEY_RELOAD);
 125
 126         return 0;
 127 }
 128
 129 static int stm32_iwdg_ping(struct watchdog_device *wdd)
 130 {
 131         struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
 132
 133         dev_dbg(wdd->parent, "%s\n", __func__);
 134
 135         /* reload watchdog */
 136         reg_write(wdt->regs, IWDG_KR, KR_KEY_RELOAD);
 137
 138         return 0;
 139 }
 140
 141 static int stm32_iwdg_set_timeout(struct watchdog_device *wdd,
 142                                   unsigned int timeout)
 143 {
 144         dev_dbg(wdd->parent, "%s timeout: %d sec\n", __func__, timeout);
 145
 146         wdd->timeout = timeout;
 147
 148         if (watchdog_active(wdd))
 149                 return stm32_iwdg_start(wdd);
 150
 151         return 0;
 152 }
 153
 154 static void stm32_clk_disable_unprepare(void *data)
 155 {
 156         clk_disable_unprepare(data);
 157 }
 158
 159 static int stm32_iwdg_clk_init(struct platform_device *pdev,
 160                                struct stm32_iwdg *wdt)
 161 {
 162         struct device *dev = &pdev->dev;
 163         u32 ret;
 164
 165         wdt->clk_lsi = devm_clk_get(dev, "lsi");
 166         if (IS_ERR(wdt->clk_lsi))
 167                 return dev_err_probe(dev, PTR_ERR(wdt->clk_lsi), "Unable to get lsi clock\n");
 168
 169         /* optional peripheral clock */
 170         if (wdt->data->has_pclk) {
 171                 wdt->clk_pclk = devm_clk_get(dev, "pclk");
 172                 if (IS_ERR(wdt->clk_pclk))
 173                         return dev_err_probe(dev, PTR_ERR(wdt->clk_pclk),
 174                                              "Unable to get pclk clock\n");
 175
 176                 ret = clk_prepare_enable(wdt->clk_pclk);
 177                 if (ret) {
 178                         dev_err(dev, "Unable to prepare pclk clock\n");
 179                         return ret;
 180                 }
 181                 ret = devm_add_action_or_reset(dev,
 182                                                stm32_clk_disable_unprepare,
 183                                                wdt->clk_pclk);
 184                 if (ret)
 185                         return ret;
 186         }
 187
 188         ret = clk_prepare_enable(wdt->clk_lsi);
 189         if (ret) {
 190                 dev_err(dev, "Unable to prepare lsi clock\n");
 191                 return ret;
 192         }
 193         ret = devm_add_action_or_reset(dev, stm32_clk_disable_unprepare,
 194                                        wdt->clk_lsi);
 195         if (ret)
 196                 return ret;
 197
 198         wdt->rate = clk_get_rate(wdt->clk_lsi);
 199
 200         return 0;
 201 }
 202
 203 static const struct watchdog_info stm32_iwdg_info = {
 204         .options        = WDIOF_SETTIMEOUT |
 205                           WDIOF_MAGICCLOSE |
 206                           WDIOF_KEEPALIVEPING,
 207         .identity       = "STM32 Independent Watchdog",
 208 };
 209
 210 static const struct watchdog_ops stm32_iwdg_ops = {
 211         .owner          = THIS_MODULE,
 212         .start          = stm32_iwdg_start,
 213         .ping           = stm32_iwdg_ping,
 214         .set_timeout    = stm32_iwdg_set_timeout,
 215 };
 216
 217 static const struct of_device_id stm32_iwdg_of_match[] = {
 218         { .compatible = "st,stm32-iwdg", .data = &stm32_iwdg_data },
 219         { .compatible = "st,stm32mp1-iwdg", .data = &stm32mp1_iwdg_data },
 220         { /* end node */ }
 221 };
 222 MODULE_DEVICE_TABLE(of, stm32_iwdg_of_match);
 223
 224 static int stm32_iwdg_probe(struct platform_device *pdev)
 225 {
 226         struct device *dev = &pdev->dev;
 227         struct watchdog_device *wdd;
 228         struct stm32_iwdg *wdt;
 229         int ret;
 230
 231         wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
 232         if (!wdt)
 233                 return -ENOMEM;
 234
 235         wdt->data = of_device_get_match_data(&pdev->dev);
 236         if (!wdt->data)
 237                 return -ENODEV;
 238
 239         /* This is the timer base. */
 240         wdt->regs = devm_platform_ioremap_resource(pdev, 0);
 241         if (IS_ERR(wdt->regs))
 242                 return PTR_ERR(wdt->regs);
 243
 244         ret = stm32_iwdg_clk_init(pdev, wdt);
 245         if (ret)
 246                 return ret;
 247
 248         /* Initialize struct watchdog_device. */
 249         wdd = &wdt->wdd;
 250         wdd->parent = dev;
 251         wdd->info = &stm32_iwdg_info;
 252         wdd->ops = &stm32_iwdg_ops;
 253         wdd->timeout = DEFAULT_TIMEOUT;
 254         wdd->min_timeout = DIV_ROUND_UP((RLR_MIN + 1) * PR_MIN, wdt->rate);
 255         wdd->max_hw_heartbeat_ms = ((RLR_MAX + 1) * wdt->data->max_prescaler *
 256                                     1000) / wdt->rate;
 257
 258         watchdog_set_drvdata(wdd, wdt);
 259         watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
 260         watchdog_init_timeout(wdd, 0, dev);
 261
 262         /*
 263          * In case of CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is set
 264          * (Means U-Boot/bootloaders leaves the watchdog running)
 265          * When we get here we should make a decision to prevent
 266          * any side effects before user space daemon will take care of it.
 267          * The best option, taking into consideration that there is no
 268          * way to read values back from hardware, is to enforce watchdog
 269          * being run with deterministic values.
 270          */
 271         if (IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) {
 272                 ret = stm32_iwdg_start(wdd);
 273                 if (ret)
 274                         return ret;
 275
 276                 /* Make sure the watchdog is serviced */
 277                 set_bit(WDOG_HW_RUNNING, &wdd->status);
 278         }
 279
 280         ret = devm_watchdog_register_device(dev, wdd);
 281         if (ret)
 282                 return ret;
 283
 284         platform_set_drvdata(pdev, wdt);
 285
 286         return 0;
 287 }
 288
 289 static struct platform_driver stm32_iwdg_driver = {
 290         .probe          = stm32_iwdg_probe,
 291         .driver = {
 292                 .name   = "iwdg",
 293                 .of_match_table = stm32_iwdg_of_match,
 294         },
 295 };
 296 module_platform_driver(stm32_iwdg_driver);
 297
 298 MODULE_AUTHOR("Yannick Fertre <yannick.fertre@st.com>");
 299 MODULE_DESCRIPTION("STMicroelectronics STM32 Independent Watchdog Driver");
 300 MODULE_LICENSE("GPL v2");