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

From: Hugo Villeneuve
Date: Fri Jan 20 2023 - 09:45:53 EST

On Fri, 20 Jan 2023 09:06:31 +0100
Philipp Rosenberger <p.rosenberger@xxxxxxxxxx> wrote:

> On 19.01.23 18:48, Hugo Villeneuve wrote:
> > On Wed, 18 Jan 2023 14:23:14 +0100
> > Philipp Rosenberger <p.rosenberger@xxxxxxxxxx> 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

Hi Philipp,
in the end this is exactly what I did. I will send an updated patch series once I have adressed the other comments.

Hugo.


> >
> >> On 15.12.22 16:02, Hugo Villeneuve wrote:
> >>> From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
> >>>
> >>> 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@xxxxxxxxxxxx>
> >>> ---
> >>> 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@xxxxxxxxxxx>
>


--
Hugo Villeneuve <hugo@xxxxxxxxxxx>