Re: [PATCH v2 2/3] watchdog: sama5d4: Fix setting timeout when watchdog is disabled

From: Guenter Roeck
Date: Sun Feb 19 2017 - 12:30:06 EST

On 02/17/2017 07:16 AM, Alexandre Belloni wrote:
On 17/02/2017 at 06:40:33 -0800, Guenter Roeck wrote:
On 02/16/2017 11:30 AM, Alexandre Belloni wrote:
The datasheet states: "When setting the WDDIS bit, and while it is set, the
fields WDV and WDD must not be modified."

Ensure WDDIS is not set when changing the timeout and set it afterwards if
the watchdog was disabled.

Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
Changes in v2:
- new patch
drivers/watchdog/sama5d4_wdt.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
index 2c6f5a70ae67..2a60251806d2 100644
--- a/drivers/watchdog/sama5d4_wdt.c
+++ b/drivers/watchdog/sama5d4_wdt.c
@@ -90,11 +90,18 @@ static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
u32 reg;

reg = wdt_read(wdt, AT91_WDT_MR);
+ if (reg & AT91_WDT_WDDIS)
+ wdt_write(wdt, AT91_WDT_MR, reg & ~AT91_WDT_WDDIS);
reg &= ~AT91_WDT_WDV;
reg &= ~AT91_WDT_WDD;
reg |= AT91_WDT_SET_WDV(value);
reg |= AT91_WDT_SET_WDD(value);
- wdt_write(wdt, AT91_WDT_MR, reg);
+ wdt_write(wdt, AT91_WDT_MR, reg & ~AT91_WDT_WDDIS);
+ if (reg & AT91_WDT_WDDIS)
+ wdt_write(wdt, AT91_WDT_MR, reg);

That means if the watchdog is running, the timeout would not be updated.
It should be updated no matter if it is running or not.

No, it is enabling the watchdog, then changing WDV and WDD and finally
disabling the watchdog if necessary. So, WDV and WDD are always changed.

You are correct. Sorry for the noise.

Seems odd that the watchdog must be _running_ to change the timeout.
Usually, if there is a restriction, it is the opposite. I hope this
doesn't cause race conditions, where the watchdog fires immediately
after being enabled due to a low timeout.