[PATCH] ppc32: m8xx watchdog update

This updates m8xx_wdt as follows:

1) Remove now obsolete fpos check in the write() function. The driver is
currently non functional due to this bug.

2) Use in/out macros for register access.

3) Allows m8xx_wdt to use a kernel timer instead of the builtin RTC/PIT
for keep-alive trigger (which is responsible for servicing the watchdog
until an userspace application takes over). For instance Cyclades PRxK
boards (MPC 855T based) have a non-functional internal RTC/PIT unit.
Behaviour for boards with RTC/PIT is unchaged.

4) The last change required moving the RTCSC register setting code
to a weak function which can be overriden by board specific files.
Otherwise the timer init code trashes the register making it impossible
for m8xx_wdt to detect the situation.
Signed-off-by: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/ppc/syslib/m8xx_setup.c

@@ -135,6 +135,16 @@ static struct irqaction tbint_irqaction = {
 	.name = "tbint",
 };
 
+/* per-board overridable init_internal_rtc() function. */
+void __init __attribute__ ((weak))
+init_internal_rtc(void)
+{
+	/* Disable the RTC one second and alarm interrupts. */
+	out_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc, in_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc) & ~(RTCSC_SIE | RTCSC_ALE));
+	/* Enable the RTC */
+	out_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc, in_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc) | (RTCSC_RTF | RTCSC_RTE));
+}
+
 /* The decrementer counts at the system (internal) clock frequency divided by
  * sixteen, or external oscillator divided by four.  We force the processor
  * to use system clock divided by sixteen.
@@ -183,10 +193,7 @@ void __init m8xx_calibrate_decr(void)
 	out_be32(&((immap_t *)IMAP_ADDR)->im_sitk.sitk_rtcsck, KAPWR_KEY);
 	out_be32(&((immap_t *)IMAP_ADDR)->im_sitk.sitk_tbk, KAPWR_KEY);
 
-	/* Disable the RTC one second and alarm interrupts. */
-	out_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc, in_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc) & ~(RTCSC_SIE | RTCSC_ALE));
-	/* Enable the RTC */
-	out_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc, in_be16(&((immap_t *)IMAP_ADDR)->im_sit.sit_rtcsc) | (RTCSC_RTF | RTCSC_RTE));
+	init_internal_rtc();
 
 	/* Enabling the decrementer also enables the timebase interrupts
 	 * (or from the other point of view, to get decrementer interrupts

arch/ppc/syslib/m8xx_wdt.c

@@ -19,6 +19,7 @@
 #include <syslib/m8xx_wdt.h>
 
 static int wdt_timeout;
+int m8xx_has_internal_rtc = 0;
 
 static irqreturn_t m8xx_wdt_interrupt(int, void *, struct pt_regs *);
 static struct irqaction m8xx_wdt_irqaction = {
@@ -45,35 +46,15 @@ static irqreturn_t m8xx_wdt_interrupt(int irq, void *dev, struct pt_regs *regs)
 	return IRQ_HANDLED;
 }
 
-void __init m8xx_wdt_handler_install(bd_t * binfo)
+#define SYPCR_SWP 0x1
+#define SYPCR_SWE 0x4
+
+
+void __init m8xx_wdt_install_irq(volatile immap_t *imap, bd_t *binfo)
 {
-	volatile immap_t *imap = (volatile immap_t *)IMAP_ADDR;
 	u32 pitc;
-	u32 sypcr;
 	u32 pitrtclk;
 
-	sypcr = in_be32(&imap->im_siu_conf.sc_sypcr);
-
-	if (!(sypcr & 0x04)) {
-		printk(KERN_NOTICE "m8xx_wdt: wdt disabled (SYPCR: 0x%08X)\n",
-		       sypcr);
-		return;
-	}
-
-	m8xx_wdt_reset();
-
-	printk(KERN_NOTICE
-	       "m8xx_wdt: active wdt found (SWTC: 0x%04X, SWP: 0x%01X)\n",
-	       (sypcr >> 16), sypcr & 0x01);
-
-	wdt_timeout = (sypcr >> 16) & 0xFFFF;
-
-	if (!wdt_timeout)
-		wdt_timeout = 0xFFFF;
-
-	if (sypcr & 0x01)
-		wdt_timeout *= 2048;
-
 	/*
 	 * Fire trigger if half of the wdt ticked down 
 	 */
@@ -98,6 +79,67 @@ void __init m8xx_wdt_handler_install(bd_t * binfo)
 	printk(KERN_NOTICE
 	       "m8xx_wdt: keep-alive trigger installed (PITC: 0x%04X)\n", pitc);
 
+}
+
+static void m8xx_wdt_timer_func(unsigned long data);
+
+static struct timer_list m8xx_wdt_timer =
+	TIMER_INITIALIZER(m8xx_wdt_timer_func, 0, 0);
+
+void m8xx_wdt_stop_timer(void)
+{
+	del_timer(&m8xx_wdt_timer);
+}
+
+void m8xx_wdt_install_timer(void)
+{
+	m8xx_wdt_timer.expires = jiffies + (HZ/2);
+	add_timer(&m8xx_wdt_timer);
+}
+
+static void m8xx_wdt_timer_func(unsigned long data)
+{
+	m8xx_wdt_reset();
+	m8xx_wdt_install_timer();
+}
+
+void __init m8xx_wdt_handler_install(bd_t * binfo)
+{
+	volatile immap_t *imap = (volatile immap_t *)IMAP_ADDR;
+	u32 sypcr;
+
+	sypcr = in_be32(&imap->im_siu_conf.sc_sypcr);
+
+	if (!(sypcr & SYPCR_SWE)) {
+		printk(KERN_NOTICE "m8xx_wdt: wdt disabled (SYPCR: 0x%08X)\n",
+		       sypcr);
+		return;
+	}
+
+	m8xx_wdt_reset();
+
+	printk(KERN_NOTICE
+	       "m8xx_wdt: active wdt found (SWTC: 0x%04X, SWP: 0x%01X)\n",
+	       (sypcr >> 16), sypcr & SYPCR_SWP);
+
+	wdt_timeout = (sypcr >> 16) & 0xFFFF;
+
+	if (!wdt_timeout)
+		wdt_timeout = 0xFFFF;
+
+	if (sypcr & SYPCR_SWP)
+		wdt_timeout *= 2048;
+
+	m8xx_has_internal_rtc = in_be16(&imap->im_sit.sit_rtcsc) & RTCSC_RTE;
+
+	/* if the internal RTC is off use a kernel timer */
+	if (!m8xx_has_internal_rtc) {
+		if (wdt_timeout < (binfo->bi_intfreq/HZ))
+			printk(KERN_ERR "m8xx_wdt: timeout too short for ktimer!\n");
+		m8xx_wdt_install_timer();
+	} else
+		m8xx_wdt_install_irq(imap, binfo);
+
 	wdt_timeout /= binfo->bi_intfreq;
 }
 

arch/ppc/syslib/m8xx_wdt.h

@@ -9,8 +9,12 @@
 #ifndef _PPC_SYSLIB_M8XX_WDT_H
 #define _PPC_SYSLIB_M8XX_WDT_H
 
+extern int m8xx_has_internal_rtc;
+
 extern void m8xx_wdt_handler_install(bd_t * binfo);
 extern int m8xx_wdt_get_timeout(void);
 extern void m8xx_wdt_reset(void);
+extern void m8xx_wdt_install_timer(void);
+extern void m8xx_wdt_stop_timer(void);
 
 #endif				/* _PPC_SYSLIB_M8XX_WDT_H */

drivers/char/watchdog/mpc8xx_wdt.c

@@ -27,7 +27,10 @@ static void mpc8xx_wdt_handler_disable(void)
 {
 	volatile immap_t *imap = (volatile immap_t *)IMAP_ADDR;
 
-	imap->im_sit.sit_piscr &= ~(PISCR_PIE | PISCR_PTE);
+	if (!m8xx_has_internal_rtc)
+		m8xx_wdt_stop_timer();
+	else
+		out_be32(imap->im_sit.sit_piscr, in_be32(&imap->im_sit.sit_piscr) & ~(PISCR_PIE | PISCR_PTE));
 
 	printk(KERN_NOTICE "mpc8xx_wdt: keep-alive handler deactivated\n");
 }
@@ -36,7 +39,10 @@ static void mpc8xx_wdt_handler_enable(void)
 {
 	volatile immap_t *imap = (volatile immap_t *)IMAP_ADDR;
 
-	imap->im_sit.sit_piscr |= PISCR_PIE | PISCR_PTE;
+	if (!m8xx_has_internal_rtc)
+		m8xx_wdt_install_timer();
+	else
+		out_be32(&imap->im_sit.sit_piscr, in_be32(&imap->im_sit.sit_piscr) | PISCR_PIE | PISCR_PTE);
 
 	printk(KERN_NOTICE "mpc8xx_wdt: keep-alive handler activated\n");
 }
@@ -68,9 +74,6 @@ static int mpc8xx_wdt_release(struct inode *inode, struct file *file)
 static ssize_t mpc8xx_wdt_write(struct file *file, const char *data, size_t len,
 				loff_t * ppos)
 {
-	if (ppos != &file->f_pos)
-		return -ESPIPE;
-
 	if (len)
 		m8xx_wdt_reset();