linux-kernel - [PATCH] hwmon: (dell-smm) Extend fan support to 5 fans

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Message-ID: <20260110034732.236285-1-android606@gmail.com>
Date: Sat, 10 Jan 2026 03:47:32 +0000
From: Andrew Mark <android606@...il.com>
To: pali@...nel.org
Cc: linux@...ck-us.net,
	linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrew Mark <android606@...il.com>
Subject: [PATCH] hwmon: (dell-smm) Extend fan support to 5 fans

Dell Precision Tower workstations have 5 fan connectors, but the
driver was limited to 4 fans after commit dbcfcb239b3b ("hwmon:
(dell-smm) Increment the number of fans").

This patch increases DELL_SMM_NO_FANS to 5 and adds the necessary
hwmon channel info for the fifth fan and its PWM control.

Without this patch, the PCIe/GPU cooling fan (fan 5) is not
controllable, which can lead to overheating on systems with
high-power fanless GPUs that depend on chassis cooling.

Also adds a DMI quirk for Precision Tower 5810 to provide accurate
fan labels, as the BIOS reports generic types for these fans.

Tested on Dell Precision Tower 5810 (BIOS A34) with all 5 fans
responding correctly to PWM control.

Fan mapping for Precision Tower 5810:
- fan0: CPU heatsink
- fan1: Second CPU (dual-CPU systems only)
- fan2: Right DIMM bank
- fan3: Left DIMM bank
- fan4: PCIe/GPU cooling

Signed-off-by: Andrew Mark <android606@...il.com>
---
 drivers/hwmon/dell-smm-hwmon.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index 6040a8940..b112e6fbc 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -74,7 +74,7 @@
 #define DELL_SMM_LEGACY_EXECUTE	0x1
 
 #define DELL_SMM_NO_TEMP	10
-#define DELL_SMM_NO_FANS	4
+#define DELL_SMM_NO_FANS	5
 
 /* limit fan multiplier to avoid overflow */
 #define DELL_SMM_MAX_FAN_MULT (INT_MAX / U16_MAX)
@@ -175,6 +175,14 @@ static const char * const docking_labels[] = {
 	"Docking Other Fan",
 };
 
+static const char * const precision_tower_5810_labels[] = {
+	"CPU Fan",
+	"CPU Fan 2",
+	"Right DIMM Fan",
+	"Left DIMM Fan",
+	"PCIe Fan",
+};
+
 static inline const char __init *i8k_get_dmi_data(int field)
 {
 	const char *dmi_data = dmi_get_system_info(field);
@@ -991,6 +999,12 @@ static const char *dell_smm_fan_label(struct dell_smm_data *data, int channel)
 	if (type < 0)
 		return ERR_PTR(type);
 
+	if (dmi_match(DMI_PRODUCT_NAME, "Precision Tower 5810")) {
+		if (channel < ARRAY_SIZE(precision_tower_5810_labels))
+			return precision_tower_5810_labels[channel];
+		return "Unknown Fan";
+	}
+
 	if (type & 0x10) {
 		dock = true;
 		type &= 0x0F;
@@ -1129,12 +1143,15 @@ static const struct hwmon_channel_info * const dell_smm_info[] = {
 			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MIN | HWMON_F_MAX |
 			   HWMON_F_TARGET,
 			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MIN | HWMON_F_MAX |
+			   HWMON_F_TARGET,
+			   HWMON_F_INPUT | HWMON_F_LABEL | HWMON_F_MIN | HWMON_F_MAX |
 			   HWMON_F_TARGET
 			   ),
 	HWMON_CHANNEL_INFO(pwm,
 			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
 			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
 			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
+			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE,
 			   HWMON_PWM_INPUT | HWMON_PWM_ENABLE
 			   ),
 	NULL
-- 
2.43.0