1 // SPDX-License-Identifier: GPL-2.0-only OR MIT 2 /* 3 * Apple SoC Watchdog driver 4 * 5 * Copyright (C) The Asahi Linux Contributors 6 */ 7 8 #include <linux/bits.h> 9 #include <linux/clk.h> 10 #include <linux/delay.h> 11 #include <linux/io.h> 12 #include <linux/kernel.h> 13 #include <linux/limits.h> 14 #include <linux/module.h> 15 #include <linux/of.h> 16 #include <linux/platform_device.h> 17 #include <linux/watchdog.h> 18 19 /* 20 * Apple Watchdog MMIO registers 21 * 22 * This HW block has three separate watchdogs. WD0 resets the machine 23 * to recovery mode and is not very useful for us. WD1 and WD2 trigger a normal 24 * machine reset. WD0 additionally supports a configurable interrupt. 25 * This information can be used to implement pretimeout support at a later time. 26 * 27 * APPLE_WDT_WDx_CUR_TIME is a simple counter incremented for each tick of the 28 * reference clock. It can also be overwritten to any value. 29 * Whenever APPLE_WDT_CTRL_RESET_EN is set in APPLE_WDT_WDx_CTRL and 30 * APPLE_WDT_WDx_CUR_TIME >= APPLE_WDT_WDx_BITE_TIME the entire machine is 31 * reset. 32 * Whenever APPLE_WDT_CTRL_IRQ_EN is set and APPLE_WDTx_WD1_CUR_TIME >= 33 * APPLE_WDTx_WD1_BARK_TIME an interrupt is triggered and 34 * APPLE_WDT_CTRL_IRQ_STATUS is set. The interrupt can be cleared by writing 35 * 1 to APPLE_WDT_CTRL_IRQ_STATUS. 36 */ 37 #define APPLE_WDT_WD0_CUR_TIME 0x00 38 #define APPLE_WDT_WD0_BITE_TIME 0x04 39 #define APPLE_WDT_WD0_BARK_TIME 0x08 40 #define APPLE_WDT_WD0_CTRL 0x0c 41 42 #define APPLE_WDT_WD1_CUR_TIME 0x10 43 #define APPLE_WDT_WD1_BITE_TIME 0x14 44 #define APPLE_WDT_WD1_CTRL 0x1c 45 46 #define APPLE_WDT_WD2_CUR_TIME 0x20 47 #define APPLE_WDT_WD2_BITE_TIME 0x24 48 #define APPLE_WDT_WD2_CTRL 0x2c 49 50 #define APPLE_WDT_CTRL_IRQ_EN BIT(0) 51 #define APPLE_WDT_CTRL_IRQ_STATUS BIT(1) 52 #define APPLE_WDT_CTRL_RESET_EN BIT(2) 53 54 #define APPLE_WDT_TIMEOUT_DEFAULT 30 55 56 struct apple_wdt { 57 struct watchdog_device wdd; 58 void __iomem *regs; 59 unsigned long clk_rate; 60 }; 61 62 static struct apple_wdt *to_apple_wdt(struct watchdog_device *wdd) 63 { 64 return container_of(wdd, struct apple_wdt, wdd); 65 } 66 67 static int apple_wdt_start(struct watchdog_device *wdd) 68 { 69 struct apple_wdt *wdt = to_apple_wdt(wdd); 70 71 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME); 72 writel_relaxed(APPLE_WDT_CTRL_RESET_EN, wdt->regs + APPLE_WDT_WD1_CTRL); 73 74 return 0; 75 } 76 77 static int apple_wdt_stop(struct watchdog_device *wdd) 78 { 79 struct apple_wdt *wdt = to_apple_wdt(wdd); 80 81 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CTRL); 82 83 return 0; 84 } 85 86 static int apple_wdt_ping(struct watchdog_device *wdd) 87 { 88 struct apple_wdt *wdt = to_apple_wdt(wdd); 89 90 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME); 91 92 return 0; 93 } 94 95 static int apple_wdt_set_timeout(struct watchdog_device *wdd, unsigned int s) 96 { 97 struct apple_wdt *wdt = to_apple_wdt(wdd); 98 99 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME); 100 writel_relaxed(wdt->clk_rate * s, wdt->regs + APPLE_WDT_WD1_BITE_TIME); 101 102 wdd->timeout = s; 103 104 return 0; 105 } 106 107 static unsigned int apple_wdt_get_timeleft(struct watchdog_device *wdd) 108 { 109 struct apple_wdt *wdt = to_apple_wdt(wdd); 110 u32 cur_time, reset_time; 111 112 cur_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME); 113 reset_time = readl_relaxed(wdt->regs + APPLE_WDT_WD1_BITE_TIME); 114 115 return (reset_time - cur_time) / wdt->clk_rate; 116 } 117 118 static int apple_wdt_restart(struct watchdog_device *wdd, unsigned long mode, 119 void *cmd) 120 { 121 struct apple_wdt *wdt = to_apple_wdt(wdd); 122 123 writel_relaxed(APPLE_WDT_CTRL_RESET_EN, wdt->regs + APPLE_WDT_WD1_CTRL); 124 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_BITE_TIME); 125 writel_relaxed(0, wdt->regs + APPLE_WDT_WD1_CUR_TIME); 126 127 /* 128 * Flush writes and then wait for the SoC to reset. Even though the 129 * reset is queued almost immediately experiments have shown that it 130 * can take up to ~20-25ms until the SoC is actually reset. Just wait 131 * 50ms here to be safe. 132 */ 133 (void)readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME); 134 mdelay(50); 135 136 return 0; 137 } 138 139 static struct watchdog_ops apple_wdt_ops = { 140 .owner = THIS_MODULE, 141 .start = apple_wdt_start, 142 .stop = apple_wdt_stop, 143 .ping = apple_wdt_ping, 144 .set_timeout = apple_wdt_set_timeout, 145 .get_timeleft = apple_wdt_get_timeleft, 146 .restart = apple_wdt_restart, 147 }; 148 149 static struct watchdog_info apple_wdt_info = { 150 .identity = "Apple SoC Watchdog", 151 .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT, 152 }; 153 154 static int apple_wdt_probe(struct platform_device *pdev) 155 { 156 struct device *dev = &pdev->dev; 157 struct apple_wdt *wdt; 158 struct clk *clk; 159 u32 wdt_ctrl; 160 161 wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL); 162 if (!wdt) 163 return -ENOMEM; 164 165 wdt->regs = devm_platform_ioremap_resource(pdev, 0); 166 if (IS_ERR(wdt->regs)) 167 return PTR_ERR(wdt->regs); 168 169 clk = devm_clk_get_enabled(dev, NULL); 170 if (IS_ERR(clk)) 171 return PTR_ERR(clk); 172 wdt->clk_rate = clk_get_rate(clk); 173 if (!wdt->clk_rate) 174 return -EINVAL; 175 176 wdt->wdd.ops = &apple_wdt_ops; 177 wdt->wdd.info = &apple_wdt_info; 178 wdt->wdd.max_timeout = U32_MAX / wdt->clk_rate; 179 wdt->wdd.timeout = APPLE_WDT_TIMEOUT_DEFAULT; 180 181 wdt_ctrl = readl_relaxed(wdt->regs + APPLE_WDT_WD1_CTRL); 182 if (wdt_ctrl & APPLE_WDT_CTRL_RESET_EN) 183 set_bit(WDOG_HW_RUNNING, &wdt->wdd.status); 184 185 watchdog_init_timeout(&wdt->wdd, 0, dev); 186 apple_wdt_set_timeout(&wdt->wdd, wdt->wdd.timeout); 187 watchdog_stop_on_unregister(&wdt->wdd); 188 watchdog_set_restart_priority(&wdt->wdd, 128); 189 190 return devm_watchdog_register_device(dev, &wdt->wdd); 191 } 192 193 static const struct of_device_id apple_wdt_of_match[] = { 194 { .compatible = "apple,wdt" }, 195 {}, 196 }; 197 MODULE_DEVICE_TABLE(of, apple_wdt_of_match); 198 199 static struct platform_driver apple_wdt_driver = { 200 .driver = { 201 .name = "apple-watchdog", 202 .of_match_table = apple_wdt_of_match, 203 }, 204 .probe = apple_wdt_probe, 205 }; 206 module_platform_driver(apple_wdt_driver); 207 208 MODULE_DESCRIPTION("Apple SoC watchdog driver"); 209 MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>"); 210 MODULE_LICENSE("Dual MIT/GPL"); 211