[PATCH v2 2/2] power: pmic: pca9450: Add support for reset status

[Primoz Fiser]

PCA9450 PMIC supports reading the reset status from the PWRON_STAT
register. Bits 7-4 give indication of the PMIC reset cause:

 - PWRON (BIT7) - Power ON triggered by PMIC_ON_REQ input line,
 - WDOGB (BIT6) - Boot after cold reset by WDOGB pin (watchdog reset),
 - SW_RST (BIT5) - Boot after cold reset initiated by the software,
 - PMIC_RST (BIT4) - Boot after PMIC_RST_B input line trigger.

Add support for reading reset status via the sysreset framework in a
convenient printable format.

Signed-off-by: Primoz Fiser <primoz.fiser at norik.com>
---
Change in v2:
- new patch as suggested by Paul Geurts

Link to v1: https://lore.kernel.org/all/20250716114547.1343797-1-primoz.fiser@norik.com/

 drivers/power/pmic/pca9450.c | 38 ++++++++++++++++++++++++++++++++++++
 include/power/pca9450.h      |  5 +++++
 2 files changed, 43 insertions(+)

diff --git a/drivers/power/pmic/pca9450.c b/drivers/power/pmic/pca9450.c
index abc39d0a1946..24426df1a49f 100644
--- a/drivers/power/pmic/pca9450.c
+++ b/drivers/power/pmic/pca9450.c
@@ -166,8 +166,46 @@ static int pca9450_sysreset_request(struct udevice *dev, enum sysreset_t type)
 	return -EINPROGRESS;
 }
 
+int pca9450_sysreset_get_status(struct udevice *dev, char *buf, int size)
+{
+	const char *reason;
+	int ret;
+	u8 reg;
+
+	ret = pmic_read(dev->parent, PCA9450_PWRON_STAT, &reg, 1);
+	if (ret)
+		return ret;
+
+	switch (reg) {
+	case PCA9450_PWRON_STAT_PWRON_MASK:
+		reason = "PWRON";
+		break;
+	case PCA9450_PWRON_STAT_WDOG_MASK:
+		reason = "WDOGB";
+		break;
+	case PCA9450_PWRON_STAT_SW_RST_MASK:
+		reason = "SW_RST";
+		break;
+	case PCA9450_PWRON_STAT_PMIC_RST_MASK:
+		reason = "PMIC_RST";
+		break;
+	default:
+		reason = "UNKNOWN";
+		break;
+	}
+
+	ret = snprintf(buf, size, "Reset Status: %s\n", reason);
+	if (ret < 0) {
+		dev_err(dev, "Write reset status error (err = %d)\n", ret);
+		return -EIO;
+	}
+
+	return 0;
+}
+
 static struct sysreset_ops pca9450_sysreset_ops = {
 	.request	= pca9450_sysreset_request,
+	.get_status	= pca9450_sysreset_get_status,
 };
 
 U_BOOT_DRIVER(pca9450_sysreset) = {
diff --git a/include/power/pca9450.h b/include/power/pca9450.h
index 9119ef793b1f..41b7f95c0340 100644
--- a/include/power/pca9450.h
+++ b/include/power/pca9450.h
@@ -75,6 +75,11 @@ enum {
 #define PCA9450_PMIC_RESET_WDOG_B_CFG_WARM		0x40
 #define PCA9450_PMIC_RESET_WDOG_B_CFG_COLD_LDO12	0x80
 
+#define PCA9450_PWRON_STAT_PWRON_MASK		0x80
+#define PCA9450_PWRON_STAT_WDOG_MASK		0x40
+#define PCA9450_PWRON_STAT_SW_RST_MASK		0x20
+#define PCA9450_PWRON_STAT_PMIC_RST_MASK		0x10
+
 #define PCA9450_SW_RST_COLD_RST		0x14
 
 #endif
-- 
2.34.1