[PATCH v2] hwmon: (pmbus) Add get_error_flags support to regulator ops

[Zev Weiss <zev@bewilderbeest.net>]

The various PMBus status bits don't all map perfectly to the more
limited set of REGULATOR_ERROR_* flags, but there's a reasonable
number where they correspond well enough.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
---

Changes since v1 [0]:
 - split patch out of power-efuse driver series
 - simplified pmbus_get_status() call
 - added comment explaining PB_STATUS_{IOUT_OC,VOUT_OV} checks
 - added fallback PB_STATUS_TEMPERATURE check mapping it to
   REGULATOR_ERROR_OVER_TEMP_WARN

[0] https://lore.kernel.org/openbmc/20220217104444.7695-2-zev@bewilderbeest.net/

 drivers/hwmon/pmbus/pmbus_core.c | 109 +++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 776ee2237be2..6f05c271bdf8 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -2417,10 +2417,119 @@ static int pmbus_regulator_disable(struct regulator_dev *rdev)
 	return _pmbus_regulator_on_off(rdev, 0);
 }
 
+/* A PMBus status flag and the corresponding REGULATOR_ERROR_* flag */
+struct pmbus_regulator_status_assoc {
+	int pflag, rflag;
+};
+
+/* PMBus->regulator bit mappings for a PMBus status register */
+struct pmbus_regulator_status_category {
+	int func;
+	int reg;
+	const struct pmbus_regulator_status_assoc *bits; /* zero-terminated */
+};
+
+static const struct pmbus_regulator_status_category pmbus_regulator_flag_map[] = {
+	{
+		.func = PMBUS_HAVE_STATUS_VOUT,
+		.reg = PMBUS_STATUS_VOUT,
+		.bits = (const struct pmbus_regulator_status_assoc[]) {
+			{ PB_VOLTAGE_UV_WARNING, REGULATOR_ERROR_UNDER_VOLTAGE_WARN },
+			{ PB_VOLTAGE_UV_FAULT,   REGULATOR_ERROR_UNDER_VOLTAGE },
+			{ PB_VOLTAGE_OV_WARNING, REGULATOR_ERROR_OVER_VOLTAGE_WARN },
+			{ PB_VOLTAGE_OV_FAULT,   REGULATOR_ERROR_REGULATION_OUT },
+			{ },
+		},
+	}, {
+		.func = PMBUS_HAVE_STATUS_IOUT,
+		.reg = PMBUS_STATUS_IOUT,
+		.bits = (const struct pmbus_regulator_status_assoc[]) {
+			{ PB_IOUT_OC_WARNING,    REGULATOR_ERROR_OVER_CURRENT_WARN },
+			{ PB_IOUT_OC_FAULT,      REGULATOR_ERROR_OVER_CURRENT },
+			{ PB_IOUT_OC_LV_FAULT,   REGULATOR_ERROR_OVER_CURRENT },
+			{ },
+		},
+	}, {
+		.func = PMBUS_HAVE_STATUS_TEMP,
+		.reg = PMBUS_STATUS_TEMPERATURE,
+		.bits = (const struct pmbus_regulator_status_assoc[]) {
+			{ PB_TEMP_OT_WARNING,    REGULATOR_ERROR_OVER_TEMP_WARN },
+			{ PB_TEMP_OT_FAULT,      REGULATOR_ERROR_OVER_TEMP },
+			{ },
+		},
+	},
+};
+
+static int pmbus_regulator_get_error_flags(struct regulator_dev *rdev, unsigned int *flags)
+{
+	int i, status;
+	const struct pmbus_regulator_status_category *cat;
+	const struct pmbus_regulator_status_assoc *bit;
+	struct device *dev = rdev_get_dev(rdev);
+	struct i2c_client *client = to_i2c_client(dev->parent);
+	struct pmbus_data *data = i2c_get_clientdata(client);
+	u8 page = rdev_get_id(rdev);
+	int func = data->info->func[page];
+
+	*flags = 0;
+
+	for (i = 0; i < ARRAY_SIZE(pmbus_regulator_flag_map); i++) {
+		cat = &pmbus_regulator_flag_map[i];
+		if (!(func & cat->func))
+			continue;
+
+		status = pmbus_read_byte_data(client, page, cat->reg);
+		if (status < 0)
+			return status;
+
+		for (bit = cat->bits; bit->pflag; bit++) {
+			if (status & bit->pflag)
+				*flags |= bit->rflag;
+		}
+	}
+
+	/*
+	 * Map what bits of STATUS_{WORD,BYTE} we can to REGULATOR_ERROR_*
+	 * bits.  Some of the other bits are tempting (especially for cases
+	 * where we don't have the relevant PMBUS_HAVE_STATUS_*
+	 * functionality), but there's an unfortunate ambiguity in that
+	 * they're defined as indicating a fault *or* a warning, so we can't
+	 * easily determine whether to report REGULATOR_ERROR_<foo> or
+	 * REGULATOR_ERROR_<foo>_WARN.
+	 */
+	status = pmbus_get_status(client, page, PMBUS_STATUS_WORD);
+	if (status < 0)
+		return status;
+
+	if (pmbus_regulator_is_enabled(rdev) && (status & PB_STATUS_OFF))
+		*flags |= REGULATOR_ERROR_FAIL;
+
+	/*
+	 * Unlike most other status bits, PB_STATUS_{IOUT_OC,VOUT_OV} are
+	 * defined strictly as fault indicators (not warnings).
+	 */
+	if (status & PB_STATUS_IOUT_OC)
+		*flags |= REGULATOR_ERROR_OVER_CURRENT;
+	if (status & PB_STATUS_VOUT_OV)
+		*flags |= REGULATOR_ERROR_REGULATION_OUT;
+
+	/*
+	 * If we haven't discovered any thermal faults or warnings via
+	 * PMBUS_STATUS_TEMPERATURE, map PB_STATUS_TEMPERATURE to a warning as
+	 * a (conservative) best-effort interpretation.
+	 */
+	if (!(*flags & (REGULATOR_ERROR_OVER_TEMP | REGULATOR_ERROR_OVER_TEMP_WARN))
+	    && (status & PB_STATUS_TEMPERATURE))
+		*flags |= REGULATOR_ERROR_OVER_TEMP_WARN;
+
+	return 0;
+}
+
 const struct regulator_ops pmbus_regulator_ops = {
 	.enable = pmbus_regulator_enable,
 	.disable = pmbus_regulator_disable,
 	.is_enabled = pmbus_regulator_is_enabled,
+	.get_error_flags = pmbus_regulator_get_error_flags,
 };
 EXPORT_SYMBOL_NS_GPL(pmbus_regulator_ops, PMBUS);
 
-- 
2.35.1