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Message-Id: <11937525802277-git-send-email-hcegtvedt@atmel.com>
Date: Tue, 30 Oct 2007 14:56:20 +0100
From: Hans-Christian Egtvedt <hcegtvedt@...el.com>
To: linux-kernel@...r.kernel.org, wim@...ana.be
Cc: Hans-Christian Egtvedt <hcegtvedt@...el.com>
Subject: [PATCH 1/1] 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@...el.com>
---
drivers/char/watchdog/at32ap700x_wdt.c | 69 ++++++++++++++++++++++++++++++--
1 files changed, 65 insertions(+), 4 deletions(-)
diff --git a/drivers/char/watchdog/at32ap700x_wdt.c b/drivers/char/watchdog/at32ap700x_wdt.c
index 54a5161..fb5ed64 100644
--- a/drivers/char/watchdog/at32ap700x_wdt.c
+++ b/drivers/char/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 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
#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 @@ struct wdt_at32ap700x {
void __iomem *regs;
spinlock_t io_lock;
int timeout;
+ int boot_status;
unsigned long users;
struct miscdevice miscdev;
};
@@ -126,7 +147,7 @@ static int at32_wdt_close(struct inode *inode, struct file *file)
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 @@ static int at32_wdt_settimeout(int time)
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 @@ static int at32_wdt_ioctl(struct inode *inode, struct file *file,
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 @@ static int __init at32_wdt_probe(struct platform_device *pdev)
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;
--
1.5.2.5
-
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