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Date: Tue, 20 Oct 2015 08:47:51 +0800 From: lizf@...nel.org To: stable@...r.kernel.org Cc: linux-kernel@...r.kernel.org, Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, Wim Van Sebroeck <wim@...ana.be>, Zefan Li <lizefan@...wei.com> Subject: [PATCH 3.4 41/65] watchdog: omap: assert the counter being stopped before reprogramming From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de> 3.4.110-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 530c11d432727c697629ad5f9d00ee8e2864d453 upstream. The omap watchdog has the annoying behaviour that writes to most registers don't have any effect when the watchdog is already running. Quoting the AM335x reference manual: To modify the timer counter value (the WDT_WCRR register), prescaler ratio (the WDT_WCLR[4:2] PTV bit field), delay configuration value (the WDT_WDLY[31:0] DLY_VALUE bit field), or the load value (the WDT_WLDR[31:0] TIMER_LOAD bit field), the watchdog timer must be disabled by using the start/stop sequence (the WDT_WSPR register). Currently the timer is stopped in the .probe callback but still there are possibilities that yield to a situation where omap_wdt_start is entered with the timer running (e.g. when /dev/watchdog is closed without stopping and then reopened). In such a case programming the timeout silently fails! To circumvent this stop the timer before reprogramming. Assuming one of the first things the watchdog user does is setting the timeout explicitly nothing too bad should happen because this explicit setting works fine. Fixes: 7768a13c252a ("[PATCH] OMAP: Add Watchdog driver support") Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de> Reviewed-by: Guenter Roeck <linux@...ck-us.net> Signed-off-by: Wim Van Sebroeck <wim@...ana.be> Signed-off-by: Zefan Li <lizefan@...wei.com> --- drivers/watchdog/omap_wdt.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/watchdog/omap_wdt.c b/drivers/watchdog/omap_wdt.c index 8285d65..c080be5 100644 --- a/drivers/watchdog/omap_wdt.c +++ b/drivers/watchdog/omap_wdt.c @@ -152,6 +152,13 @@ static int omap_wdt_open(struct inode *inode, struct file *file) pm_runtime_get_sync(wdev->dev); + /* + * Make sure the watchdog is disabled. This is unfortunately required + * because writing to various registers with the watchdog running has no + * effect. + */ + omap_wdt_disable(wdev); + /* initialize prescaler */ while (__raw_readl(base + OMAP_WATCHDOG_WPS) & 0x01) cpu_relax(); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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