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Date:   Thu, 21 Nov 2019 06:21:26 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Christophe ROULLIER <christophe.roullier@st.com>
Cc:     "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
        "mcoquelin.stm32@gmail.com" <mcoquelin.stm32@gmail.com>,
        Alexandre TORGUE <alexandre.torgue@st.com>,
        "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-stm32@st-md-mailman.stormreply.com" 
        <linux-stm32@st-md-mailman.stormreply.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/1] drivers: watchdog: stm32_iwdg: set WDOG_HW_RUNNING
 at probe
Message-ID: <20191121142126.GB13249@roeck-us.net>
References: <20191121082813.29267-1-christophe.roullier@st.com>
 <20191121082813.29267-2-christophe.roullier@st.com>
 <ce10681c-8fa3-0fa6-3509-376a2f37aec9@roeck-us.net>
 <550566ff-31bd-1f40-63d1-67b013f8be75@st.com>
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On Thu, Nov 21, 2019 at 01:45:21PM +0000, Christophe ROULLIER wrote:
> Hi Guenter,
> 
> On 11/21/19 10:53 AM, Guenter Roeck wrote:
> > On 11/21/19 12:28 AM, Christophe Roullier wrote:
> >> If the watchdog hardware is already enabled during the boot process,
> >> when the Linux watchdog driver loads, it should reset the watchdog and
> >> tell the watchdog framework. As a result, ping can be generated from
> >> the watchdog framework (if CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED is set),
> >> until the userspace watchdog daemon takes over control
> >>
> >
> > This is not what the code is doing. It sets the WDOG_HW_RUNNING flag
> > unconditionally, no matter if the watchdog is already running or not.
> > It also changes the semantic of the rest of the code, as well as
> > functionality. The code in start_timeout no longer waits, and the ping
> > code explicitly (re-)enables the watchdog.
> >
> > If you want an option to start the watchdog at probe time 
> > unconditionally,
> > please add a module parameter to do it. Otherwise you'll need to check if
> > it is indeed enabled before setting WDOG_HW_RUNNING, and in that case it
> > should not be necessary to re-enable it. It should also not be necessary
> > to split the start function.
> 
> With our IWDG IP, there is no way to read values from hardware (if it is 
> running or not)
> 
> We are in same case of intel-mid_wdt.c driver, we have Uboot which can
> 
> leaves the watchdog running. So we need to force the kicking of our 
> watchdog.
> 

"can" or "leaves" ? 

Anyway, if that is the case, please follow the guidance from intel-mid_wdt.c,
and explain it accordingly. Alternatively, please explain why something like

	ret = wdt_start(wdt_dev);
        if (ret)
                return ret;

	/* Make sure the watchdog is serviced */
        set_bit(WDOG_HW_RUNNING, &wdt_dev->status);

would not work in your case, and why all that added complexity
is needed.

Thanks,
Guenter

> Thanks
> 
> Christophe
> 
> >
> > Thanks,
> > Guenter
> >
> >> Fixes:4332d113c66a ("watchdog: Add STM32 IWDG driver")
> >> Signed-off-by: Christophe Roullier <christophe.roullier@st.com>
> >> ---
> >> ? drivers/watchdog/stm32_iwdg.c | 57 ++++++++++++++++++++++++-----------
> >> ? 1 file changed, 40 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/drivers/watchdog/stm32_iwdg.c 
> >> b/drivers/watchdog/stm32_iwdg.c
> >> index a3a329011a06..2b3be3b1c15b 100644
> >> --- a/drivers/watchdog/stm32_iwdg.c
> >> +++ b/drivers/watchdog/stm32_iwdg.c
> >> @@ -87,8 +87,23 @@ static inline void reg_write(void __iomem *base, 
> >> u32 reg, u32 val)
> >> ? static int stm32_iwdg_start(struct watchdog_device *wdd)
> >> ? {
> >> ????? struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
> >> -??? u32 tout, presc, iwdg_rlr, iwdg_pr, iwdg_sr;
> >> -??? int ret;
> >> +
> >> +??? dev_dbg(wdd->parent, "%s\n", __func__);
> >> +
> >> +??? /*? Start the watchdog */
> >> +??? reg_write(wdt->regs, IWDG_KR, KR_KEY_ENABLE);
> >> +
> >> +??? /* reload watchdog */
> >> +??? reg_write(wdt->regs, IWDG_KR, KR_KEY_RELOAD);
> >> +
> >> +??? set_bit(WDOG_HW_RUNNING, &wdd->status);
> >> +??? return 0;
> >> +}
> >> +
> >> +static int stm32_iwdg_setprescaler(struct watchdog_device *wdd)
> >> +{
> >> +??? struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
> >> +??? u32 tout, presc, iwdg_rlr, iwdg_pr;
> >> ? ????? dev_dbg(wdd->parent, "%s\n", __func__);
> >> ? @@ -108,19 +123,6 @@ static int stm32_iwdg_start(struct 
> >> watchdog_device *wdd)
> >> ????? /* set prescaler & reload registers */
> >> ????? reg_write(wdt->regs, IWDG_PR, iwdg_pr);
> >> ????? reg_write(wdt->regs, IWDG_RLR, iwdg_rlr);
> >> -??? reg_write(wdt->regs, IWDG_KR, KR_KEY_ENABLE);
> >> -
> >> -??? /* wait for the registers to be updated (max 100ms) */
> >> -??? ret = readl_relaxed_poll_timeout(wdt->regs + IWDG_SR, iwdg_sr,
> >> -???????????????????? !(iwdg_sr & (SR_PVU | SR_RVU)),
> >> -???????????????????? SLEEP_US, TIMEOUT_US);
> >> -??? if (ret) {
> >> -??????? dev_err(wdd->parent, "Fail to set prescaler, reload regs\n");
> >> -??????? return ret;
> >> -??? }
> >> -
> >> -??? /* reload watchdog */
> >> -??? reg_write(wdt->regs, IWDG_KR, KR_KEY_RELOAD);
> >> ? ????? return 0;
> >> ? }
> >> @@ -131,6 +133,9 @@ static int stm32_iwdg_ping(struct watchdog_device 
> >> *wdd)
> >> ? ????? dev_dbg(wdd->parent, "%s\n", __func__);
> >> ? +??? /*? Start the watchdog */
> >> +??? reg_write(wdt->regs, IWDG_KR, KR_KEY_ENABLE);
> >> +
> >> ????? /* reload watchdog */
> >> ????? reg_write(wdt->regs, IWDG_KR, KR_KEY_RELOAD);
> >> ? @@ -140,12 +145,21 @@ static int stm32_iwdg_ping(struct 
> >> watchdog_device *wdd)
> >> ? static int stm32_iwdg_set_timeout(struct watchdog_device *wdd,
> >> ??????????????????? unsigned int timeout)
> >> ? {
> >> +??? int ret;
> >> +
> >> ????? dev_dbg(wdd->parent, "%s timeout: %d sec\n", __func__, timeout);
> >> ? ????? wdd->timeout = timeout;
> >> ? -??? if (watchdog_active(wdd))
> >> -??????? return stm32_iwdg_start(wdd);
> >> +??? if (watchdog_active(wdd)) {
> >> +??????? ret = stm32_iwdg_setprescaler(wdd);
> >> +??????? if (ret) {
> >> +??????????? dev_err(wdd->parent, "failed to set prescaler\n");
> >> +??????????? return ret;
> >> +??????? } else {
> >> +??????????? return stm32_iwdg_start(wdd);
> >> +??????? }
> >> +??? }
> >> ? ????? return 0;
> >> ? }
> >> @@ -262,12 +276,21 @@ static int stm32_iwdg_probe(struct 
> >> platform_device *pdev)
> >> ????? watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);
> >> ????? watchdog_init_timeout(wdd, 0, dev);
> >> ? +??? /* Make sure the watchdog is serviced */
> >> +??? set_bit(WDOG_HW_RUNNING, &wdd->status);
> >> +
> >> ????? ret = devm_watchdog_register_device(dev, wdd);
> >> ????? if (ret)
> >> ????????? return ret;
> >> ? ????? platform_set_drvdata(pdev, wdt);
> >> ? +??? ret = stm32_iwdg_setprescaler(wdd);
> >> +??? if (ret) {
> >> +??????? dev_err(dev, "failed to set prescaler\n");
> >> +??????? return ret;
> >> +??? }
> >> +
> >> ????? return 0;
> >> ? }
> >>
> >