On 02/03/2017 at 09:42:24 -0800, Guenter Roeck wrote:
> On Thu, Mar 02, 2017 at 06:31:12PM +0100, Alexandre Belloni wrote:
> > WDT_MR and WDT_CR must not updated within three slow clock periods after
> > the last ping (write to WDT_CR or WDT_MR). Ensure enough time has elapsed
> > before writing those registers.
> > wdt_write() waits for 4 periods to ensure at least 3 edges are seen by the
> > IP.
> >
>
> Would it be possible to use min_hw_heartbeat_ms for this purpose ?
>
I don't think so unless you want the core to also use that delay between
__watchdog_ping, watchdog_start, watchdog_set_timeout and watchdog_stop.
Currently, it is only between two calls of __watchdog_ping,
> Thanks,
> Guenter
>
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/watchdog/sama5d4_wdt.c | 33 +++++++++++++++++++++++++++++----
> > 1 file changed, 29 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
> > index 5cee20caca78..362fd229786d 100644
> > --- a/drivers/watchdog/sama5d4_wdt.c
> > +++ b/drivers/watchdog/sama5d4_wdt.c
> > @@ -6,6 +6,7 @@
> > * Licensed under GPLv2.
> > */
> >
> > +#include <linux/delay.h>
> > #include <linux/interrupt.h>
> > #include <linux/io.h>
> > #include <linux/kernel.h>
> > @@ -29,6 +30,7 @@ struct sama5d4_wdt {
> > struct watchdog_device wdd;
> > void __iomem *reg_base;
> > u32 mr;
> > + unsigned long last_ping;
> > };
> >
> > static int wdt_timeout = WDT_DEFAULT_TIMEOUT;
> > @@ -49,8 +51,29 @@ MODULE_PARM_DESC(nowayout,
> > #define wdt_read(wdt, field) \
> > readl_relaxed((wdt)->reg_base + (field))
> >
> > -#define wdt_write(wtd, field, val) \
> > - writel_relaxed((val), (wdt)->reg_base + (field))
> > +/* 4 slow clock periods is 4/32768 = 122.07µs*/
> > +#define WDT_DELAY usecs_to_jiffies(123)
> > +
> > +static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
> > +{
> > + /*
> > + * WDT_CR and WDT_MR must not be modified within three slow clock
> > + * periods following a restart of the watchdog performed by a write
> > + * access in WDT_CR.
> > + */
> > + while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
> > + usleep_range(30, 125);
> > + writel_relaxed(val, wdt->reg_base + field);
> > + wdt->last_ping = jiffies;
> > +}
> > +
> > +static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val)
> > +{
> > + if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
> > + udelay(123);
> > + writel_relaxed(val, wdt->reg_base + field);
> > + wdt->last_ping = jiffies;
> > +}
> >
> > static int sama5d4_wdt_start(struct watchdog_device *wdd)
> > {
> > @@ -164,11 +187,12 @@ static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
> > * Else, we have to disable it properly.
> > */
> > if (wdt_enabled) {
> > - wdt_write(wdt, AT91_WDT_MR, wdt->mr);
> > + wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
> > } else {
> > reg = wdt_read(wdt, AT91_WDT_MR);
> > if (!(reg & AT91_WDT_WDDIS))
> > - wdt_write(wdt, AT91_WDT_MR, reg | AT91_WDT_WDDIS);
> > + wdt_write_nosleep(wdt, AT91_WDT_MR,
> > + reg | AT91_WDT_WDDIS);
> > }
> > return 0;
> > }
> > @@ -193,6 +217,7 @@ static int sama5d4_wdt_probe(struct platform_device *pdev)
> > wdd->ops = &sama5d4_wdt_ops;
> > wdd->min_timeout = MIN_WDT_TIMEOUT;
> > wdd->max_timeout = MAX_WDT_TIMEOUT;
> > + wdt->last_ping = jiffies;
> >
> > watchdog_set_drvdata(wdd, wdt);
> >
> > --
> > 2.11.0
> >
--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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