[WATCHDOG] at32ap700x_wdt: add support for boot status and add fix for silicon errata

This patch enables the watchdog to read out the reset cause after a boot and provide this to the user. The driver will now also return -EIO if probed when booting from a watchdog reset. This is due to a silicon errata in the AT32AP700x devices. Detailed description and work-arounds can be found in the errata section of the datasheet avilable from http://www.atmel.com/dyn/products/datasheets.asp?family_id=682 Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com> Signed-off-by: Wim Van Sebroeck <wim@iguana.be> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

[WATCHDOG] at32ap700x_wdt: add support for boot status and add fix for silicon errata
This patch enables the watchdog to read out the reset cause after a boot and provide this to the user. The driver will now also return -EIO if probed when booting from a watchdog reset. This is due to a silicon errata in the AT32AP700x devices. Detailed description and work-arounds can be found in the errata section of the datasheet avilable from http://www.atmel.com/dyn/products/datasheets.asp?family_id=682 Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com> Signed-off-by: Wim Van Sebroeck <wim@iguana.be> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Hans-Christian Egtvedt · Wim Van Sebroeck
1 parent 2ffbb8377c
Showing 1 changed file with 65 additions and 4 deletions Side-by-side Diff
drivers/watchdog/at32ap700x_wdt.c
@@ -6,6 +6,19 @@
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
+ *
+ *
+ * Errata: WDT Clear is blocked after WDT Reset
+ *
+ * A watchdog timer event will, after reset, block writes to the WDT_CLEAR
+ * register, preventing the program to clear the next Watchdog Timer Reset.
+ *
+ * If you still want to use the WDT after a WDT reset a small code can be
+ * insterted at the startup checking the AVR32_PM.rcause register for WDT reset
+ * and use a GPIO pin to reset the system. This method requires that one of the
+ * GPIO pins are available and connected externally to the RESET_N pin. After
+ * the GPIO pin has pulled down the reset line the GPIO will be reset and leave
+ * the pin tristated with pullup.
  */
  
 #include <linux/init.h>
@@ -44,6 +57,13 @@
  
 #define WDT_CLR			0x04
  
+#define WDT_RCAUSE		0x10
+#define WDT_RCAUSE_POR		   0
+#define WDT_RCAUSE_EXT		   2
+#define WDT_RCAUSE_WDT		   3
+#define WDT_RCAUSE_JTAG		   4
+#define WDT_RCAUSE_SERP		   5
+
 #define WDT_BIT(name)		(1 << WDT_##name)
 #define WDT_BF(name, value)	((value) << WDT_##name)
  
@@ -56,6 +76,7 @@
 	void __iomem		*regs;
 	spinlock_t		io_lock;
 	int			timeout;
+	int			boot_status;
 	unsigned long		users;
 	struct miscdevice	miscdev;
 };
@@ -126,7 +147,7 @@
 		at32_wdt_stop();
 	} else {
 		dev_dbg(wdt->miscdev.parent,
-			"Unexpected close, not stopping watchdog!\n");
+			"unexpected close, not stopping watchdog!\n");
 		at32_wdt_pat();
 	}
 	clear_bit(1, &wdt->users);
@@ -154,6 +175,33 @@
 	return 0;
 }
  
+/*
+ * Get the watchdog status.
+ */
+static int at32_wdt_get_status(void)
+{
+	int rcause;
+	int status = 0;
+
+	rcause = wdt_readl(wdt, RCAUSE);
+
+	switch (rcause) {
+	case WDT_BIT(RCAUSE_EXT):
+		status = WDIOF_EXTERN1;
+		break;
+	case WDT_BIT(RCAUSE_WDT):
+		status = WDIOF_CARDRESET;
+		break;
+	case WDT_BIT(RCAUSE_POR):  /* fall through */
+	case WDT_BIT(RCAUSE_JTAG): /* fall through */
+	case WDT_BIT(RCAUSE_SERP): /* fall through */
+	default:
+		break;
+	}
+
+	return status;
+}
+
 static struct watchdog_info at32_wdt_info = {
 	.identity	= "at32ap700x watchdog",
 	.options	= WDIOF_SETTIMEOUT |
  
@@ -194,10 +242,12 @@
 	case WDIOC_GETTIMEOUT:
 		ret = put_user(wdt->timeout, p);
 		break;
-	case WDIOC_GETSTATUS: /* fall through */
-	case WDIOC_GETBOOTSTATUS:
+	case WDIOC_GETSTATUS:
 		ret = put_user(0, p);
 		break;
+	case WDIOC_GETBOOTSTATUS:
+		ret = put_user(wdt->boot_status, p);
+		break;
 	case WDIOC_SETOPTIONS:
 		ret = get_user(time, p);
 		if (ret)
  
@@ -282,8 +332,19 @@
 		dev_dbg(&pdev->dev, "could not map I/O memory\n");
 		goto err_free;
 	}
+
 	spin_lock_init(&wdt->io_lock);
-	wdt->users = 0;
+	wdt->boot_status = at32_wdt_get_status();
+
+	/* Work-around for watchdog silicon errata. */
+	if (wdt->boot_status & WDIOF_CARDRESET) {
+		dev_info(&pdev->dev, "CPU must be reset with external "
+				"reset or POR due to silicon errata.\n");
+		ret = -EIO;
+		goto err_iounmap;
+	} else {
+		wdt->users = 0;
+	}
 	wdt->miscdev.minor = WATCHDOG_MINOR;
 	wdt->miscdev.name = "watchdog";
 	wdt->miscdev.fops = &at32_wdt_fops;
...	...	@@ -6,6 +6,19 @@
6	6	* This program is free software; you can redistribute it and/or modify
7	7	* it under the terms of the GNU General Public License version 2 as
8	8	* published by the Free Software Foundation.
	9	+ *
	10	+ *
	11	+ * Errata: WDT Clear is blocked after WDT Reset
	12	+ *
	13	+ * A watchdog timer event will, after reset, block writes to the WDT_CLEAR
	14	+ * register, preventing the program to clear the next Watchdog Timer Reset.
	15	+ *
	16	+ * If you still want to use the WDT after a WDT reset a small code can be
	17	+ * insterted at the startup checking the AVR32_PM.rcause register for WDT reset
	18	+ * and use a GPIO pin to reset the system. This method requires that one of the
	19	+ * GPIO pins are available and connected externally to the RESET_N pin. After
	20	+ * the GPIO pin has pulled down the reset line the GPIO will be reset and leave
	21	+ * the pin tristated with pullup.
9	22	*/
10	23
11	24	#include <linux/init.h>
...	...	@@ -44,6 +57,13 @@
44	57
45	58	#define WDT_CLR 0x04
46	59
	60	+#define WDT_RCAUSE 0x10
	61	+#define WDT_RCAUSE_POR 0
	62	+#define WDT_RCAUSE_EXT 2
	63	+#define WDT_RCAUSE_WDT 3
	64	+#define WDT_RCAUSE_JTAG 4
	65	+#define WDT_RCAUSE_SERP 5
	66	+
47	67	#define WDT_BIT(name) (1 << WDT_##name)
48	68	#define WDT_BF(name, value) ((value) << WDT_##name)
49	69
...	...	@@ -56,6 +76,7 @@
56	76	void __iomem *regs;
57	77	spinlock_t io_lock;
58	78	int timeout;
	79	+ int boot_status;
59	80	unsigned long users;
60	81	struct miscdevice miscdev;
61	82	};
...	...	@@ -126,7 +147,7 @@
126	147	at32_wdt_stop();
127	148	} else {
128	149	dev_dbg(wdt->miscdev.parent,
129		- "Unexpected close, not stopping watchdog!\n");
	150	+ "unexpected close, not stopping watchdog!\n");
130	151	at32_wdt_pat();
131	152	}
132	153	clear_bit(1, &wdt->users);
...	...	@@ -154,6 +175,33 @@
154	175	return 0;
155	176	}
156	177
	178	+/*
	179	+ * Get the watchdog status.
	180	+ */
	181	+static int at32_wdt_get_status(void)
	182	+{
	183	+ int rcause;
	184	+ int status = 0;
	185	+
	186	+ rcause = wdt_readl(wdt, RCAUSE);
	187	+
	188	+ switch (rcause) {
	189	+ case WDT_BIT(RCAUSE_EXT):
	190	+ status = WDIOF_EXTERN1;
	191	+ break;
	192	+ case WDT_BIT(RCAUSE_WDT):
	193	+ status = WDIOF_CARDRESET;
	194	+ break;
	195	+ case WDT_BIT(RCAUSE_POR): /* fall through */
	196	+ case WDT_BIT(RCAUSE_JTAG): /* fall through */
	197	+ case WDT_BIT(RCAUSE_SERP): /* fall through */
	198	+ default:
	199	+ break;
	200	+ }
	201	+
	202	+ return status;
	203	+}
	204	+
157	205	static struct watchdog_info at32_wdt_info = {
158	206	.identity = "at32ap700x watchdog",
159	207	.options = WDIOF_SETTIMEOUT \|
160	208
...	...	@@ -194,10 +242,12 @@
194	242	case WDIOC_GETTIMEOUT:
195	243	ret = put_user(wdt->timeout, p);
196	244	break;
197		- case WDIOC_GETSTATUS: /* fall through */
198		- case WDIOC_GETBOOTSTATUS:
	245	+ case WDIOC_GETSTATUS:
199	246	ret = put_user(0, p);
200	247	break;
	248	+ case WDIOC_GETBOOTSTATUS:
	249	+ ret = put_user(wdt->boot_status, p);
	250	+ break;
201	251	case WDIOC_SETOPTIONS:
202	252	ret = get_user(time, p);
203	253	if (ret)
204	254
...	...	@@ -282,8 +332,19 @@
282	332	dev_dbg(&pdev->dev, "could not map I/O memory\n");
283	333	goto err_free;
284	334	}
	335	+
285	336	spin_lock_init(&wdt->io_lock);
286		- wdt->users = 0;
	337	+ wdt->boot_status = at32_wdt_get_status();
	338	+
	339	+ /* Work-around for watchdog silicon errata. */
	340	+ if (wdt->boot_status & WDIOF_CARDRESET) {
	341	+ dev_info(&pdev->dev, "CPU must be reset with external "
	342	+ "reset or POR due to silicon errata.\n");
	343	+ ret = -EIO;
	344	+ goto err_iounmap;
	345	+ } else {
	346	+ wdt->users = 0;
	347	+ }
287	348	wdt->miscdev.minor = WATCHDOG_MINOR;
288	349	wdt->miscdev.name = "watchdog";
289	350	wdt->miscdev.fops = &at32_wdt_fops;