Re: [PATCH v3 12/14] rtc: pcf2127: support generic watchdog timing configuration

[Philipp Rosenberger <p.rosenberger@kunbus.com>]

On 19.01.23 18:48, Hugo Villeneuve wrote:
> On Wed, 18 Jan 2023 14:23:14 +0100
> Philipp Rosenberger <p.rosenberger@kunbus.com> wrote:
> 
> Hi Philipp,
> you are right that the value store/computed inside the structure wdd (struct watchdog_device) should be in seconds, according to the header file documentation in watchdog.h.
> 
> However, in the PCF2127 datasheet, the value n that is stored in the PCF2127_REG_WD_VAL register does not represent a value in seconds, but a counter value. It is given by this equation:
> 
>      n = source_clock_frequency x timer_period_in_seconds
> 
> For the PCF2127, since the clock used is 1Hz, it works as the previous equation can be simplified as:
> 
>      n = timer_period_in_seconds
> 
> However, if the source clock is different than 1Hz, it would no longer work. Also, since the PCF2131 uses a default clock of 1/4 Hz, it also would not work.
> 
> That is the reason why I modified the watchdog timer value (n) computation to take the clock into account. I then use the desired timeout in seconds given by  PCF2127_WD_VAL_DEFAULT to compute the counter value (n).
> 
> So what I am proposing to do is to store the PCF2127_WD_VAL_DEFAULT value in wdd->timeout, as before, but convert it to a counter value in pcf2127_wdt_active_ping(). Or to only compute it once, I could define a new variable and compute/set it in pcf2127_watchdog_init().
> 
> Hugo.
> 

Hi Hugo,

with some small changes to your code I was able to get the behavior 
right. But with this the timeout get converted from seconds to the 
counter register format on every ping.

Just add WD_COUNTER(wdd->timeout, pcf2127->cfg->wdd_clock_hz_x1000) to 
the regmap_write() in pcf2127_wdt_ping(). Then in 
pcf2127_watchdog_init() just do:

pcf2127->wdd.timeout = PCF2127_WD_VAL_DEFAULT;

Best regards,
Philipp

> 
>> On 15.12.22 16:02, Hugo Villeneuve wrote:
>>> From: Hugo Villeneuve <hvilleneuve@dimonoff.com>
>>>
>>> Introduce in the configuration structure two new values to hold the
>>> watchdog clock source and the min_hw_heartbeat_ms value.
>>>
>>> The minimum and maximum timeout values are automatically computed from
>>> the watchdog clock source value for each variant.
>>>
>>> The PCF2131 has no 1Hz watchdog clock source, as is the case for
>>> PCF2127/29.
>>>
>>> The next best choice is using a 1/4Hz clock, giving a watchdog timeout
>>> range between 4 and 1016s. By using the same register configuration as
>>> for the PCF2127/29, the 1/4Hz clock source is selected.
>>>
>>> Note: the PCF2127 datasheet gives a min/max range between 1 and 255s,
>>> but it should be between 2 and 254s, because the watchdog is triggered
>>> when the timer value reaches 1, not 0.
>>>
>>> Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
>>> ---
>>>    drivers/rtc/rtc-pcf2127.c | 56 +++++++++++++++++++++++++++++++++------
>>>    1 file changed, 48 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
>>> index 11fbdab6bf01..3fd2fee4978b 100644
>>> --- a/drivers/rtc/rtc-pcf2127.c
>>> +++ b/drivers/rtc/rtc-pcf2127.c
>>> @@ -157,9 +157,29 @@
>>>
>>>    /* Watchdog timer value constants */
>>>    #define PCF2127_WD_VAL_STOP               0
>>> -#define PCF2127_WD_VAL_MIN         2
>>> -#define PCF2127_WD_VAL_MAX         255
>>> -#define PCF2127_WD_VAL_DEFAULT             60
>>> +#define PCF2127_WD_VAL_DEFAULT             60 /* In seconds. */
>>> +/* PCF2127/29 watchdog timer value constants */
>>> +#define PCF2127_WD_CLOCK_HZ_X1000  1000 /* 1Hz */
>>> +#define PCF2127_WD_MIN_HW_HEARTBEAT_MS     500
>>> +/* PCF2131 watchdog timer value constants */
>>> +#define PCF2131_WD_CLOCK_HZ_X1000  250  /* 1/4Hz */
>>> +#define PCF2131_WD_MIN_HW_HEARTBEAT_MS     4000
>>> +/*
>>> + * Compute watchdog period, t, in seconds, from the WATCHDG_TIM_VAL register
>>> + * value, n, and the clock frequency, f, in Hz.
>>> + *
>>> + * The PCF2127/29 datasheet gives t as:
>>> + *   t = n / f
>>> + * The PCF2131 datasheet gives t as:
>>> + *   t = (n - 1) / f
>>> + * For both variants, the watchdog is triggered when the WATCHDG_TIM_VAL reaches
>>> + * the value 1, and not zero. Consequently, the equation from the PCF2131
>>> + * datasheet seems to be the correct one for both variants.
>>> + */
>>> +#define WD_PERIOD_S(_n_, _f1000_) ((1000 * ((_n_) - 1)) / (_f1000_))
>>> +
>>> +/* Compute value of WATCHDG_TIM_VAL to obtain period t, in seconds. */
>>> +#define WD_COUNTER(_t_, _f1000_) ((((_t_) * (_f1000_)) / 1000) + 1)
>>>
>>>    /* Mask for currently enabled interrupts */
>>>    #define PCF2127_CTRL1_IRQ_MASK (PCF2127_BIT_CTRL1_TSF1)
>>> @@ -202,6 +222,11 @@ struct pcf21xx_config {
>>>      u8 reg_wd_val; /* Watchdog value register. */
>>>      u8 reg_clkout; /* Clkout register. */
>>>      u8 reg_reset;  /* Reset register if available. */
>>> +
>>> +   /* Watchdog configuration. */
>>> +   int wdd_clock_hz_x1000; /* Value in Hz multiplicated by 1000 */
>>> +   int wdd_min_hw_heartbeat_ms;
>>> +
>>>      unsigned int ts_count;
>>>      struct pcf21xx_ts_config ts[4];
>>>      struct attribute_group attribute_group;
>>> @@ -496,10 +521,19 @@ static int pcf2127_watchdog_init(struct device *dev, struct pcf2127 *pcf2127)
>>>      pcf2127->wdd.parent = dev;
>>>      pcf2127->wdd.info = &pcf2127_wdt_info;
>>>      pcf2127->wdd.ops = &pcf2127_watchdog_ops;
>>> -   pcf2127->wdd.min_timeout = PCF2127_WD_VAL_MIN;
>>> -   pcf2127->wdd.max_timeout = PCF2127_WD_VAL_MAX;
>>> -   pcf2127->wdd.timeout = PCF2127_WD_VAL_DEFAULT;
>>> -   pcf2127->wdd.min_hw_heartbeat_ms = 500;
>>> +
>>> +   pcf2127->wdd.min_timeout =
>>> +           WD_PERIOD_S(2, pcf2127->cfg->wdd_clock_hz_x1000);
>>> +   pcf2127->wdd.max_timeout =
>>> +           WD_PERIOD_S(255, pcf2127->cfg->wdd_clock_hz_x1000);
>>> +   pcf2127->wdd.timeout = WD_COUNTER(PCF2127_WD_VAL_DEFAULT,
>>> +                                     pcf2127->cfg->wdd_clock_hz_x1000);
>>> +
>>> +   dev_dbg(dev, "%s min = %ds\n", __func__, pcf2127->wdd.min_timeout);
>>> +   dev_dbg(dev, "%s max = %ds\n", __func__, pcf2127->wdd.max_timeout);
>>> +   dev_dbg(dev, "%s def = %d\n", __func__, pcf2127->wdd.timeout);
>>> +
>>> +   pcf2127->wdd.min_hw_heartbeat_ms = pcf2127->cfg->wdd_min_hw_heartbeat_ms;
>>>      pcf2127->wdd.status = WATCHDOG_NOWAYOUT_INIT_STATUS;
>>>
>>>      watchdog_set_drvdata(&pcf2127->wdd, pcf2127);
>>> @@ -926,6 +960,8 @@ static struct pcf21xx_config pcf21xx_cfg[] = {
>>>              .reg_wd_ctl = PCF2127_REG_WD_CTL,
>>>              .reg_wd_val = PCF2127_REG_WD_VAL,
>>>              .reg_clkout = PCF2127_REG_CLKOUT,
>>> +           .wdd_clock_hz_x1000 = PCF2127_WD_CLOCK_HZ_X1000,
>>> +           .wdd_min_hw_heartbeat_ms = PCF2127_WD_MIN_HW_HEARTBEAT_MS,
>>>              .ts_count = 1,
>>>              .ts[0] = {
>>>                      .regs_base = PCF2127_REG_TS1_BASE,
>>> @@ -951,6 +987,8 @@ static struct pcf21xx_config pcf21xx_cfg[] = {
>>>              .reg_wd_ctl = PCF2127_REG_WD_CTL,
>>>              .reg_wd_val = PCF2127_REG_WD_VAL,
>>>              .reg_clkout = PCF2127_REG_CLKOUT,
>>> +           .wdd_clock_hz_x1000 = PCF2127_WD_CLOCK_HZ_X1000,
>>> +           .wdd_min_hw_heartbeat_ms = PCF2127_WD_MIN_HW_HEARTBEAT_MS,
>>>              .ts_count = 1,
>>>              .ts[0] = {
>>>                      .regs_base = PCF2127_REG_TS1_BASE,
>>> @@ -977,6 +1015,8 @@ static struct pcf21xx_config pcf21xx_cfg[] = {
>>>              .reg_wd_val = PCF2131_REG_WD_VAL,
>>>              .reg_clkout = PCF2131_REG_CLKOUT,
>>>              .reg_reset  = PCF2131_REG_SR_RESET,
>>> +           .wdd_clock_hz_x1000 = PCF2131_WD_CLOCK_HZ_X1000,
>>> +           .wdd_min_hw_heartbeat_ms = PCF2131_WD_MIN_HW_HEARTBEAT_MS,
>>>              .ts_count = 4,
>>>              .ts[0] = {
>>>                      .regs_base = PCF2131_REG_TS1_BASE,
>>> @@ -1215,7 +1255,7 @@ static int pcf2127_probe(struct device *dev, struct regmap *regmap,
>>>
>>>      /*
>>>       * Watchdog timer enabled and reset pin /RST activated when timed out.
>>> -    * Select 1Hz clock source for watchdog timer.
>>> +    * Select 1Hz clock source for watchdog timer (1/4Hz for PCF2131).
>>>       * Note: Countdown timer disabled and not available.
>>>       * For pca2129, pcf2129 and pcf2131, only bit[7] is for Symbol WD_CD
>>>       * of register watchdg_tim_ctl. The bit[6] is labeled
>>
> 
> 
> --
> Hugo Villeneuve <hugo@hugovil.com>