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

[zumeng.chen@windriver.com (Zumeng Chen)]

? 2012?06?18? 13:23, 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@ti.com>
> Acked-by: Santosh Shilimkar<santosh.shilimkar@ti.com>
> Cc: Wim Van Sebroeck<wim@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");
> 	}
> }
Hello, Lokesh,

One question: Does "echo 1 > /dev/watchdog" work well?

Regards,
Zumeng
> - 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;