[PATCH] platform/x86: hp-wmi: Use only the low byte of the thermal profile

[Akhil Boyapati <boyakhil978@gmail.com>]

On the HP Spectre x360 14 (board 8C15) the firmware answers the
thermal profile query (0x4C, read) with more than the profile: the
DSDT's GTPS method returns the profile in byte 0, OEM flags in byte 1
and the device posture in byte 2. In Quiet mode in laptop posture the
value is 0x00041103.

thermal_profile_get() returns the whole value, so
hp_wmi_platform_profile_get() matches no profile and reading
/sys/firmware/acpi/platform_profile fails with -EINVAL. This also
breaks power-profiles-daemon and tuned-ppd. Probe writes the
unmasked value back, which only works because the firmware's write
method (STPS) uses byte 0.

Mask the value to its low byte. Boards that return only the profile
are unaffected.

Tested on board 8C15 (kernel 7.2.11, module built from this tree's
driver with the change applied): platform_profile reads back correctly
after setting each of cool, quiet, balanced and performance, and the
firmware's ODVP0 follows (3, 4, 2, 1). Not tested on other boards.

Fixes: 4296f679ca50 ("platform/x86: hp-wmi: add platform profile support")
Assisted-by: LLM
Signed-off-by: Akhil Boyapati <boyakhil978@gmail.com>
---
 drivers/platform/x86/hp/hp-wmi.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/hp/hp-wmi.c b/drivers/platform/x86/hp/hp-wmi.c
index 52077833a..6180f1d21 100644
--- a/drivers/platform/x86/hp/hp-wmi.c
+++ b/drivers/platform/x86/hp/hp-wmi.c
@@ -2117,7 +2117,13 @@ static int platform_profile_omen_set(struct device *dev,
 
 static int thermal_profile_get(void)
 {
-	return hp_wmi_read_int(HPWMI_THERMAL_PROFILE_QUERY);
+	int tp = hp_wmi_read_int(HPWMI_THERMAL_PROFILE_QUERY);
+
+	/*
+	 * Only the low byte is the thermal profile. Some firmware (e.g. board
+	 * 8C15) packs OEM flags and the device posture into the upper bytes.
+	 */
+	return tp < 0 ? tp : tp & 0xff;
 }
 
 static int thermal_profile_set(int thermal_profile)
-- 
2.56.0