1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Renesas RZ/A Series WDT Driver 4 * 5 * Copyright (C) 2017 Renesas Electronics America, Inc. 6 * Copyright (C) 2017 Chris Brandt 7 */ 8 9 #include <linux/bitops.h> 10 #include <linux/clk.h> 11 #include <linux/delay.h> 12 #include <linux/io.h> 13 #include <linux/module.h> 14 #include <linux/of.h> 15 #include <linux/platform_device.h> 16 #include <linux/watchdog.h> 17 18 #define DEFAULT_TIMEOUT 30 19 20 /* Watchdog Timer Registers */ 21 #define WTCSR 0 22 #define WTCSR_MAGIC 0xA500 23 #define WTSCR_WT BIT(6) 24 #define WTSCR_TME BIT(5) 25 #define WTSCR_CKS(i) (i) 26 27 #define WTCNT 2 28 #define WTCNT_MAGIC 0x5A00 29 30 #define WRCSR 4 31 #define WRCSR_MAGIC 0x5A00 32 #define WRCSR_RSTE BIT(6) 33 #define WRCSR_CLEAR_WOVF 0xA500 /* special value */ 34 35 /* The maximum CKS register setting value to get the longest timeout */ 36 #define CKS_3BIT 0x7 37 #define CKS_4BIT 0xF 38 39 #define DIVIDER_3BIT 16384 /* Clock divider when CKS = 0x7 */ 40 #define DIVIDER_4BIT 4194304 /* Clock divider when CKS = 0xF */ 41 42 struct rza_wdt { 43 struct watchdog_device wdev; 44 void __iomem *base; 45 struct clk *clk; 46 u8 count; 47 u8 cks; 48 }; 49 50 static void rza_wdt_calc_timeout(struct rza_wdt *priv, int timeout) 51 { 52 unsigned long rate = clk_get_rate(priv->clk); 53 unsigned int ticks; 54 55 if (priv->cks == CKS_4BIT) { 56 ticks = DIV_ROUND_UP(timeout * rate, DIVIDER_4BIT); 57 58 /* 59 * Since max_timeout was set in probe, we know that the timeout 60 * value passed will never calculate to a tick value greater 61 * than 256. 62 */ 63 priv->count = 256 - ticks; 64 65 } else { 66 /* Start timer with longest timeout */ 67 priv->count = 0; 68 } 69 70 pr_debug("%s: timeout set to %u (WTCNT=%d)\n", __func__, 71 timeout, priv->count); 72 } 73 74 static int rza_wdt_start(struct watchdog_device *wdev) 75 { 76 struct rza_wdt *priv = watchdog_get_drvdata(wdev); 77 78 /* Stop timer */ 79 writew(WTCSR_MAGIC | 0, priv->base + WTCSR); 80 81 /* Must dummy read WRCSR:WOVF at least once before clearing */ 82 readb(priv->base + WRCSR); 83 writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR); 84 85 rza_wdt_calc_timeout(priv, wdev->timeout); 86 87 writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR); 88 writew(WTCNT_MAGIC | priv->count, priv->base + WTCNT); 89 writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME | 90 WTSCR_CKS(priv->cks), priv->base + WTCSR); 91 92 return 0; 93 } 94 95 static int rza_wdt_stop(struct watchdog_device *wdev) 96 { 97 struct rza_wdt *priv = watchdog_get_drvdata(wdev); 98 99 writew(WTCSR_MAGIC | 0, priv->base + WTCSR); 100 101 return 0; 102 } 103 104 static int rza_wdt_ping(struct watchdog_device *wdev) 105 { 106 struct rza_wdt *priv = watchdog_get_drvdata(wdev); 107 108 writew(WTCNT_MAGIC | priv->count, priv->base + WTCNT); 109 110 pr_debug("%s: timeout = %u\n", __func__, wdev->timeout); 111 112 return 0; 113 } 114 115 static int rza_set_timeout(struct watchdog_device *wdev, unsigned int timeout) 116 { 117 wdev->timeout = timeout; 118 rza_wdt_start(wdev); 119 return 0; 120 } 121 122 static int rza_wdt_restart(struct watchdog_device *wdev, unsigned long action, 123 void *data) 124 { 125 struct rza_wdt *priv = watchdog_get_drvdata(wdev); 126 127 /* Stop timer */ 128 writew(WTCSR_MAGIC | 0, priv->base + WTCSR); 129 130 /* Must dummy read WRCSR:WOVF at least once before clearing */ 131 readb(priv->base + WRCSR); 132 writew(WRCSR_CLEAR_WOVF, priv->base + WRCSR); 133 134 /* 135 * Start timer with fastest clock source and only 1 clock left before 136 * overflow with reset option enabled. 137 */ 138 writew(WRCSR_MAGIC | WRCSR_RSTE, priv->base + WRCSR); 139 writew(WTCNT_MAGIC | 255, priv->base + WTCNT); 140 writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME, priv->base + WTCSR); 141 142 /* 143 * Actually make sure the above sequence hits hardware before sleeping. 144 */ 145 wmb(); 146 147 /* Wait for WDT overflow (reset) */ 148 udelay(20); 149 150 return 0; 151 } 152 153 static const struct watchdog_info rza_wdt_ident = { 154 .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT, 155 .identity = "Renesas RZ/A WDT Watchdog", 156 }; 157 158 static const struct watchdog_ops rza_wdt_ops = { 159 .owner = THIS_MODULE, 160 .start = rza_wdt_start, 161 .stop = rza_wdt_stop, 162 .ping = rza_wdt_ping, 163 .set_timeout = rza_set_timeout, 164 .restart = rza_wdt_restart, 165 }; 166 167 static int rza_wdt_probe(struct platform_device *pdev) 168 { 169 struct device *dev = &pdev->dev; 170 struct rza_wdt *priv; 171 unsigned long rate; 172 int ret; 173 174 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); 175 if (!priv) 176 return -ENOMEM; 177 178 priv->base = devm_platform_ioremap_resource(pdev, 0); 179 if (IS_ERR(priv->base)) 180 return PTR_ERR(priv->base); 181 182 priv->clk = devm_clk_get(dev, NULL); 183 if (IS_ERR(priv->clk)) 184 return PTR_ERR(priv->clk); 185 186 rate = clk_get_rate(priv->clk); 187 if (rate < 16384) { 188 dev_err(dev, "invalid clock rate (%ld)\n", rate); 189 return -ENOENT; 190 } 191 192 priv->wdev.info = &rza_wdt_ident; 193 priv->wdev.ops = &rza_wdt_ops; 194 priv->wdev.parent = dev; 195 196 priv->cks = (u8)(uintptr_t) of_device_get_match_data(dev); 197 if (priv->cks == CKS_4BIT) { 198 /* Assume slowest clock rate possible (CKS=0xF) */ 199 priv->wdev.max_timeout = (DIVIDER_4BIT * U8_MAX) / rate; 200 201 } else if (priv->cks == CKS_3BIT) { 202 /* Assume slowest clock rate possible (CKS=7) */ 203 rate /= DIVIDER_3BIT; 204 205 /* 206 * Since the max possible timeout of our 8-bit count 207 * register is less than a second, we must use 208 * max_hw_heartbeat_ms. 209 */ 210 priv->wdev.max_hw_heartbeat_ms = (1000 * U8_MAX) / rate; 211 dev_dbg(dev, "max hw timeout of %dms\n", 212 priv->wdev.max_hw_heartbeat_ms); 213 } 214 215 priv->wdev.min_timeout = 1; 216 priv->wdev.timeout = DEFAULT_TIMEOUT; 217 218 watchdog_init_timeout(&priv->wdev, 0, dev); 219 watchdog_set_drvdata(&priv->wdev, priv); 220 221 ret = devm_watchdog_register_device(dev, &priv->wdev); 222 if (ret) 223 dev_err(dev, "Cannot register watchdog device\n"); 224 225 return ret; 226 } 227 228 static const struct of_device_id rza_wdt_of_match[] = { 229 { .compatible = "renesas,r7s9210-wdt", .data = (void *)CKS_4BIT, }, 230 { .compatible = "renesas,rza-wdt", .data = (void *)CKS_3BIT, }, 231 { /* sentinel */ } 232 }; 233 MODULE_DEVICE_TABLE(of, rza_wdt_of_match); 234 235 static struct platform_driver rza_wdt_driver = { 236 .probe = rza_wdt_probe, 237 .driver = { 238 .name = "rza_wdt", 239 .of_match_table = rza_wdt_of_match, 240 }, 241 }; 242 243 module_platform_driver(rza_wdt_driver); 244 245 MODULE_DESCRIPTION("Renesas RZ/A WDT Driver"); 246 MODULE_AUTHOR("Chris Brandt <chris.brandt@renesas.com>"); 247 MODULE_LICENSE("GPL v2"); 248