[PATCH 3/3] ACPI: PMIC: xpower: Fix _TMP ACPI errors

[Hans de Goede <hdegoede@redhat.com>]

On some devices with a X-Powers AXP288 PMIC the LPAT tables in the ACPI
node for the AXP288 PMIC for some reason only describe a small temperature
range, e.g. 27° - 37° Celcius (assuming the entries are in millidegrees).

When the tablet is idle in a room at 21° degrees this is causing values
outside the LPAT table to be read, causing e.g. the following 2 errors
to get spammed to the logs every 4 seconds! :

[ 7512.791316] ACPI Error: AE_ERROR, Returned by Handler for [UserDefinedRegion] (20210930/evregion-281)
[ 7512.791611] ACPI Error: Aborting method \_SB.SXP1._TMP due to previous error (AE_ERROR) (20210930/psparse-529)

Fix this by clamping the raw value to the LPAT table range before
passing it to acpi_lpat_raw_to_temp().

Note clamping has been chosen rather then extrapolating because it is
unknown how other parts of the ACPI tables will respond to temperature
values outside of the LPAT range.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/acpi/pmic/intel_pmic_xpower.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/pmic/intel_pmic_xpower.c b/drivers/acpi/pmic/intel_pmic_xpower.c
index e844bc1f3df5..61bbe4c24d87 100644
--- a/drivers/acpi/pmic/intel_pmic_xpower.c
+++ b/drivers/acpi/pmic/intel_pmic_xpower.c
@@ -293,12 +293,33 @@ static int intel_xpower_exec_mipi_pmic_seq_element(struct regmap *regmap,
 	return ret;
 }
 
+static int intel_xpower_lpat_raw_to_temp(struct acpi_lpat_conversion_table *lpat_table,
+					 int raw)
+{
+	struct acpi_lpat first = lpat_table->lpat[0];
+	struct acpi_lpat last = lpat_table->lpat[lpat_table->lpat_count - 1];
+
+	/*
+	 * Some LPAT tables in the ACPI Device for the AXP288 PMIC for some
+	 * reason only describe a small temperature range, e.g. 27° - 37°
+	 * Celcius. Resulting in errors when the tablet is idle in a cool room.
+	 *
+	 * To avoid these errors clamp the raw value to be inside the LPAT.
+	 */
+	if (first.raw < last.raw)
+		raw = clamp(raw, first.raw, last.raw);
+	else
+		raw = clamp(raw, last.raw, first.raw);
+
+	return acpi_lpat_raw_to_temp(lpat_table, raw);
+}
+
 static const struct intel_pmic_opregion_data intel_xpower_pmic_opregion_data = {
 	.get_power = intel_xpower_pmic_get_power,
 	.update_power = intel_xpower_pmic_update_power,
 	.get_raw_temp = intel_xpower_pmic_get_raw_temp,
 	.exec_mipi_pmic_seq_element = intel_xpower_exec_mipi_pmic_seq_element,
-	.lpat_raw_to_temp = acpi_lpat_raw_to_temp,
+	.lpat_raw_to_temp = intel_xpower_lpat_raw_to_temp,
 	.power_table = power_table,
 	.power_table_count = ARRAY_SIZE(power_table),
 	.thermal_table = thermal_table,
-- 
2.33.1