rtc: pcf2127: add flag for watchdog register value read support

The watchdog value register cannot be read on the PCF2131 after being
set.

Add a new flag to identify which variant has read access to this
register, and use this flag to selectively test if watchdog timer was
started by bootloader.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Reviewed-by: Bruno Thomsen <bruno.thomsen@gmail.com>
Link: https://lore.kernel.org/r/20230622145800.2442116-16-hugo@hugovil.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
index 59c0dcf..3acab5a 100644 (file)
--- a/drivers/rtc/rtc-pcf2127.c
+++ b/drivers/rtc/rtc-pcf2127.c
@@ -185,6 +185,7 @@ struct pcf21xx_config {
        int max_register;
        unsigned int has_nvmem:1;
        unsigned int has_bit_wd_ctl_cd0:1;
+       unsigned int wd_val_reg_readable:1; /* If watchdog value register can be read. */
        unsigned int has_int_a_b:1; /* PCF2131 supports two interrupt outputs. */
        u8 reg_time_base; /* Time/date base register. */
        u8 regs_alarm_base; /* Alarm function base registers. */
@@ -486,7 +487,6 @@ static int pcf2127_watchdog_get_period(int n, int f1000)
 
 static int pcf2127_watchdog_init(struct device *dev, struct pcf2127 *pcf2127)
 {
-       u32 wdd_timeout;
        int ret;
 
        if (!IS_ENABLED(CONFIG_WATCHDOG) ||
@@ -514,12 +514,17 @@ static int pcf2127_watchdog_init(struct device *dev, struct pcf2127 *pcf2127)
        watchdog_set_drvdata(&pcf2127->wdd, pcf2127);
 
        /* Test if watchdog timer is started by bootloader */
-       ret = regmap_read(pcf2127->regmap, pcf2127->cfg->reg_wd_val, &wdd_timeout);
-       if (ret)
-               return ret;
+       if (pcf2127->cfg->wd_val_reg_readable) {
+               u32 wdd_timeout;
+
+               ret = regmap_read(pcf2127->regmap, pcf2127->cfg->reg_wd_val,
+                                 &wdd_timeout);
+               if (ret)
+                       return ret;
 
-       if (wdd_timeout)
-               set_bit(WDOG_HW_RUNNING, &pcf2127->wdd.status);
+               if (wdd_timeout)
+                       set_bit(WDOG_HW_RUNNING, &pcf2127->wdd.status);
+       }
 
        return devm_watchdog_register_device(dev, &pcf2127->wdd);
 }
@@ -919,6 +924,7 @@ static struct pcf21xx_config pcf21xx_cfg[] = {
                .max_register = 0x1d,
                .has_nvmem = 1,
                .has_bit_wd_ctl_cd0 = 1,
+               .wd_val_reg_readable = 1,
                .has_int_a_b = 0,
                .reg_time_base = PCF2127_REG_TIME_BASE,
                .regs_alarm_base = PCF2127_REG_ALARM_BASE,
@@ -946,6 +952,7 @@ static struct pcf21xx_config pcf21xx_cfg[] = {
                .max_register = 0x19,
                .has_nvmem = 0,
                .has_bit_wd_ctl_cd0 = 0,
+               .wd_val_reg_readable = 1,
                .has_int_a_b = 0,
                .reg_time_base = PCF2127_REG_TIME_BASE,
                .regs_alarm_base = PCF2127_REG_ALARM_BASE,
@@ -973,6 +980,7 @@ static struct pcf21xx_config pcf21xx_cfg[] = {
                .max_register = 0x36,
                .has_nvmem = 0,
                .has_bit_wd_ctl_cd0 = 0,
+               .wd_val_reg_readable = 0,
                .has_int_a_b = 1,
                .reg_time_base = PCF2131_REG_TIME_BASE,
                .regs_alarm_base = PCF2131_REG_ALARM_BASE,