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Message-ID: <550566ff-31bd-1f40-63d1-67b013f8be75@st.com>
Date: Thu, 21 Nov 2019 13:45:21 +0000
From: Christophe ROULLIER <christophe.roullier@...com>
To: Guenter Roeck <linux@...ck-us.net>,
"wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
"mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
Alexandre TORGUE <alexandre.torgue@...com>
CC: "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-stm32@...md-mailman.stormreply.com"
<linux-stm32@...md-mailman.stormreply.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/1] drivers: watchdog: stm32_iwdg: set WDOG_HW_RUNNING at
probe
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.
Thanks
Christophe
>
> Thanks,
> Guenter
>
>> Fixes:4332d113c66a ("watchdog: Add STM32 IWDG driver")
>> Signed-off-by: Christophe Roullier <christophe.roullier@...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;
>> }
>>
>
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