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    SubjectRE: [PATCH V2 1/2] watchdog: imx7ulp: Strictly follow the sequence for wdog operations
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    Hi, Guenter


    > Subject: RE: [PATCH V2 1/2] watchdog: imx7ulp: Strictly follow the sequence
    > for wdog operations
    >
    > Hi, Guenter
    >
    >
    > > Subject: Re: [PATCH V2 1/2] watchdog: imx7ulp: Strictly follow the
    > > sequence for wdog operations
    > >
    > > On 7/28/20 7:20 PM, Anson Huang wrote:
    > > > According to reference manual, the i.MX7ULP WDOG's operations should
    > > > follow below sequence:
    > > >
    > > > 1. disable global interrupts;
    > > > 2. unlock the wdog and wait unlock bit set; 3. reconfigure the wdog
    > > > and wait for reconfiguration bit set; 4. enabel global interrupts.
    > > >
    > > > Strictly follow the recommended sequence can make it more robust.
    > > >
    > > > Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
    > > > ---
    > > > Changes since V1:
    > > > - use readl_poll_timeout_atomic() instead of usleep_ranges() since
    > > > IRQ is
    > > disabled.
    > > > ---
    > > > drivers/watchdog/imx7ulp_wdt.c | 29 +++++++++++++++++++++++++++++
    > > > 1 file changed, 29 insertions(+)
    > > >
    > > > diff --git a/drivers/watchdog/imx7ulp_wdt.c
    > > > b/drivers/watchdog/imx7ulp_wdt.c index 7993c8c..7d2b12e 100644
    > > > --- a/drivers/watchdog/imx7ulp_wdt.c
    > > > +++ b/drivers/watchdog/imx7ulp_wdt.c
    > > > @@ -5,6 +5,7 @@
    > > >
    > > > #include <linux/clk.h>
    > > > #include <linux/io.h>
    > > > +#include <linux/iopoll.h>
    > > > #include <linux/kernel.h>
    > > > #include <linux/module.h>
    > > > #include <linux/of.h>
    > > > @@ -36,6 +37,7 @@
    > > > #define DEFAULT_TIMEOUT 60
    > > > #define MAX_TIMEOUT 128
    > > > #define WDOG_CLOCK_RATE 1000
    > > > +#define WDOG_WAIT_TIMEOUT 10000
    > > >
    > > > static bool nowayout = WATCHDOG_NOWAYOUT;
    > > module_param(nowayout,
    > > > bool, 0000); @@ -48,17 +50,31 @@ struct imx7ulp_wdt_device {
    > > > struct clk *clk;
    > > > };
    > > >
    > > > +static inline void imx7ulp_wdt_wait(void __iomem *base, u32 mask) {
    > > > + u32 val = readl(base + WDOG_CS);
    > > > +
    > > > + if (!(val & mask))
    > > > + WARN_ON(readl_poll_timeout_atomic(base + WDOG_CS, val,
    > > > + val & mask, 0,
    > > > + WDOG_WAIT_TIMEOUT));
    > >
    > > I am not a friend of WARN_ON, especially in situations like this.
    > > Please explain why this is needed, and why a return of -ETIMEDOUT is
    > > not feasible.
    >
    > OK, I will use return value of -ETIMEOUT and handle it in the caller.

    After a further look, some of the imx7ulp_wdt_wait () callers are void function, so if want
    to handle the return value, all those functions return type need to be changed. And, when
    the return value is -ETIMEDOUT, the ONLY action is to print out some error message
    for these void function, need to use pr_err() due to no dev pointer available, so
    do you think it is acceptable to just replace the WARN_ON with pr_err() as below?

    + if (!(val & mask)) {
    + if (readl_poll_timeout_atomic(base + WDOG_CS, val,
    + val & mask, 0,
    + WDOG_WAIT_TIMEOUT))
    + pr_err("wdog wait timeout, mask 0x%x\n", mask);
    + }

    Thanks,
    Anson

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