[PATCH] Watchdog: OMAP: Fix the runtime pm code to avoid module getting stuck intransition state.

[Lokesh Vutla]

OMAP watchdong driver is adapted to runtime PM like a general device
driver but it is not appropriate. It is causing couple of functional
issues. 

1. On OMAP4 SYSCLK can't be gated, because of issue with WDTIMER2 module,
which constantly stays in "in transition" state. Value of register
CM_WKUP_WDTIMER2_CLKCTRL is always 0x00010000 in this case.
Issue occurs immediately after first idle, when hwmod framework tries
to disable WDTIMER2 functional clock - "wd_timer2_fck". After this
module falls to "in transition" state, and SYSCLK gating is blocked.

2. Due to runtime PM, watchdog timer may be completely disabled.
In current code base watchdog timer is not disabled only because of
issue 1. Otherwise state of WDTIMER2 module will be "Disabled", and there
will be no interrupts from omap_wdt. In other words watchdog will not
work at all.

Watchdong is a special IP and it should not be disabled otherwise
purpose of it itself is defeated. Watchdog functional clock should
never be disabled. This patch updates the runtime PM handling in
driver so that runtime PM is limited only during probe/shutdown
and suspend/resume.

The patch fixes issue 1 and 2 

Signed-off-by: Lokesh Vutla <lokeshvutla at ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
Cc: Wim Van Sebroeck <wim at iguana.be>
---
Tested on OMAP4430SDP.

Issue #1 can be easily reproduced on mainline kernel.
- Take latest mainline kernel and create uImage using omap2plus_defconfig
- Write a program to open watchdog,like
void main(void)
{
	int fd = open("/dev/watchdog", O_WRONLY);

	if (fd == -1) {
		perror("Watchdog device interface is not available!\n");
	}
}  
- Build with arm compiler and copy it to your file syatem
- Boot the image and run the executable.


 drivers/watchdog/omap_wdt.c |   17 -----------------
 1 files changed, 0 insertions(+), 17 deletions(-)

diff --git a/drivers/watchdog/omap_wdt.c b/drivers/watchdog/omap_wdt.c
index 8285d65..27ab8db 100644
--- a/drivers/watchdog/omap_wdt.c
+++ b/drivers/watchdog/omap_wdt.c
@@ -126,8 +126,6 @@ static void omap_wdt_set_timeout(struct omap_wdt_dev *wdev)
 	u32 pre_margin = GET_WLDR_VAL(timer_margin);
 	void __iomem *base = wdev->base;
 
-	pm_runtime_get_sync(wdev->dev);
-
 	/* just count up at 32 KHz */
 	while (__raw_readl(base + OMAP_WATCHDOG_WPS) & 0x04)
 		cpu_relax();
@@ -135,8 +133,6 @@ static void omap_wdt_set_timeout(struct omap_wdt_dev *wdev)
 	__raw_writel(pre_margin, base + OMAP_WATCHDOG_LDR);
 	while (__raw_readl(base + OMAP_WATCHDOG_WPS) & 0x04)
 		cpu_relax();
-
-	pm_runtime_put_sync(wdev->dev);
 }
 
 /*
@@ -166,8 +162,6 @@ static int omap_wdt_open(struct inode *inode, struct file *file)
 	omap_wdt_ping(wdev); /* trigger loading of new timeout value */
 	omap_wdt_enable(wdev);
 
-	pm_runtime_put_sync(wdev->dev);
-
 	return nonseekable_open(inode, file);
 }
 
@@ -179,8 +173,6 @@ static int omap_wdt_release(struct inode *inode, struct file *file)
 	 *      Shut off the timer unless NOWAYOUT is defined.
 	 */
 #ifndef CONFIG_WATCHDOG_NOWAYOUT
-	pm_runtime_get_sync(wdev->dev);
-
 	omap_wdt_disable(wdev);
 
 	pm_runtime_put_sync(wdev->dev);
@@ -199,11 +191,9 @@ static ssize_t omap_wdt_write(struct file *file, const char __user *data,
 
 	/* Refresh LOAD_TIME. */
 	if (len) {
-		pm_runtime_get_sync(wdev->dev);
 		spin_lock(&wdt_lock);
 		omap_wdt_ping(wdev);
 		spin_unlock(&wdt_lock);
-		pm_runtime_put_sync(wdev->dev);
 	}
 	return len;
 }
@@ -236,18 +226,15 @@ static long omap_wdt_ioctl(struct file *file, unsigned int cmd,
 					(int __user *)arg);
 		return put_user(0, (int __user *)arg);
 	case WDIOC_KEEPALIVE:
-		pm_runtime_get_sync(wdev->dev);
 		spin_lock(&wdt_lock);
 		omap_wdt_ping(wdev);
 		spin_unlock(&wdt_lock);
-		pm_runtime_put_sync(wdev->dev);
 		return 0;
 	case WDIOC_SETTIMEOUT:
 		if (get_user(new_margin, (int __user *)arg))
 			return -EFAULT;
 		omap_wdt_adjust_timeout(new_margin);
 
-		pm_runtime_get_sync(wdev->dev);
 		spin_lock(&wdt_lock);
 		omap_wdt_disable(wdev);
 		omap_wdt_set_timeout(wdev);
@@ -255,7 +242,6 @@ static long omap_wdt_ioctl(struct file *file, unsigned int cmd,
 
 		omap_wdt_ping(wdev);
 		spin_unlock(&wdt_lock);
-		pm_runtime_put_sync(wdev->dev);
 		/* Fall */
 	case WDIOC_GETTIMEOUT:
 		return put_user(timer_margin, (int __user *)arg);
@@ -363,7 +349,6 @@ static void omap_wdt_shutdown(struct platform_device *pdev)
 	struct omap_wdt_dev *wdev = platform_get_drvdata(pdev);
 
 	if (wdev->omap_wdt_users) {
-		pm_runtime_get_sync(wdev->dev);
 		omap_wdt_disable(wdev);
 		pm_runtime_put_sync(wdev->dev);
 	}
@@ -403,7 +388,6 @@ static int omap_wdt_suspend(struct platform_device *pdev, pm_message_t state)
 	struct omap_wdt_dev *wdev = platform_get_drvdata(pdev);
 
 	if (wdev->omap_wdt_users) {
-		pm_runtime_get_sync(wdev->dev);
 		omap_wdt_disable(wdev);
 		pm_runtime_put_sync(wdev->dev);
 	}
@@ -419,7 +403,6 @@ static int omap_wdt_resume(struct platform_device *pdev)
 		pm_runtime_get_sync(wdev->dev);
 		omap_wdt_enable(wdev);
 		omap_wdt_ping(wdev);
-		pm_runtime_put_sync(wdev->dev);
 	}
 
 	return 0;
-- 
1.7.5.4