[PATCH] asus-wmi: Support the hardware GPU MUX on some laptops

[Luke D. Jones]

Support the hardware GPU MUX switch available on some models. This
switch can toggle the MUX between:

- 0, Dedicated mode
- 1, Optimus mode

Optimus mode is the regular iGPU + dGPU available, while dedicated
mode switches the system to have only the dGPU available.

Signed-off-by: Luke D. Jones <luke@xxxxxxxxxx>
---
 .../ABI/testing/sysfs-platform-asus-wmi       | 11 ++++
 drivers/platform/x86/asus-wmi.c               | 62 +++++++++++++++++++
 include/linux/platform_data/x86/asus-wmi.h    |  3 +
 3 files changed, 76 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-platform-asus-wmi b/Documentation/ABI/testing/sysfs-platform-asus-wmi
index 574b5170a37d..03124eab7f01 100644
--- a/Documentation/ABI/testing/sysfs-platform-asus-wmi
+++ b/Documentation/ABI/testing/sysfs-platform-asus-wmi
@@ -58,6 +58,17 @@ Description:
 			* 1 - overboost,
 			* 2 - silent
 
+What:          /sys/devices/platform/<platform>/gpu_mux_mode
+Date:          Aug 2022
+KernelVersion: 6.1
+Contact:       "Luke Jones" <luke@xxxxxxxxxx>
+Description:
+               Switch the GPU hardware MUX mode. Laptops with this feature can
+			   can be toggled to boot with only the dGPU (discrete mode) or in
+			   standard Optimus/Hybrid mode. On switch a reboot is required:
+                       * 0 - Discrete GPU,
+                       * 1 - Optimus/Hybrid,
+
 What:          /sys/devices/platform/<platform>/dgpu_disable
 Date:          Aug 2022
 KernelVersion: 5.17
diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index e2b51b5550e8..0421ffb81927 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -230,6 +230,7 @@ struct asus_wmi {
 
 	bool egpu_enable_available;
 	bool dgpu_disable_available;
+	bool gpu_mux_mode_available;
 
 	bool throttle_thermal_policy_available;
 	u8 throttle_thermal_policy_mode;
@@ -668,6 +669,59 @@ static ssize_t egpu_enable_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(egpu_enable);
 
+/* gpu mux switch *************************************************************/
+static int gpu_mux_mode_check_present(struct asus_wmi *asus)
+{
+	asus->gpu_mux_mode_available = asus_wmi_dev_is_present(asus, ASUS_WMI_DEVID_GPU_MUX);
+
+   return 0;
+}
+
+static ssize_t gpu_mux_mode_show(struct device *dev,
+                  struct device_attribute *attr, char *buf)
+{
+   struct asus_wmi *asus = dev_get_drvdata(dev);
+   int result;
+
+   result = asus_wmi_get_devstate_simple(asus, ASUS_WMI_DEVID_GPU_MUX);
+   if (result < 0)
+       return result;
+
+   return sysfs_emit(buf, "%d\n", result);
+}
+
+static ssize_t gpu_mux_mode_store(struct device *dev,
+                   struct device_attribute *attr,
+                   const char *buf, size_t count)
+{
+   struct asus_wmi *asus = dev_get_drvdata(dev);
+   int result, err;
+   u32 optimus;
+
+   err = kstrtou32(buf, 10, &optimus);
+   if (err)
+       return err;
+
+   if (optimus > 1)
+       return -EINVAL;
+
+   err = asus_wmi_set_devstate(ASUS_WMI_DEVID_GPU_MUX, optimus, &result);
+   if (err) {
+       dev_err(dev, "Failed to set GPU MUX mode: %d\n", err);
+       return err;
+   }
+	/* !1 is considered a fail by ASUS */
+	if (result != 1) {
+		dev_warn(dev, "Failed to set GPU MUX mode (result): 0x%x\n", result);
+       return -EIO;
+   }
+
+   sysfs_notify(&asus->platform_device->dev.kobj, NULL, "gpu_mux_mode");
+
+   return count;
+}
+static DEVICE_ATTR_RW(gpu_mux_mode);
+
 /* Battery ********************************************************************/
 
 /* The battery maximum charging percentage */
@@ -3165,6 +3219,7 @@ static struct attribute *platform_attributes[] = {
 	&dev_attr_touchpad.attr,
 	&dev_attr_egpu_enable.attr,
 	&dev_attr_dgpu_disable.attr,
+	&dev_attr_gpu_mux_mode.attr,
 	&dev_attr_lid_resume.attr,
 	&dev_attr_als_enable.attr,
 	&dev_attr_fan_boost_mode.attr,
@@ -3195,6 +3250,8 @@ static umode_t asus_sysfs_is_visible(struct kobject *kobj,
 		ok = asus->egpu_enable_available;
 	else if (attr == &dev_attr_dgpu_disable.attr)
 		ok = asus->dgpu_disable_available;
+	else if (attr == &dev_attr_gpu_mux_mode.attr)
+		ok = asus->gpu_mux_mode_available;
 	else if (attr == &dev_attr_fan_boost_mode.attr)
 		ok = asus->fan_boost_mode_available;
 	else if (attr == &dev_attr_throttle_thermal_policy.attr)
@@ -3464,6 +3521,10 @@ static int asus_wmi_add(struct platform_device *pdev)
 	if (err)
 		goto fail_dgpu_disable;
 
+	err = gpu_mux_mode_check_present(asus);
+   if (err)
+       goto fail_gpu_mux_mode;
+
 	err = fan_boost_mode_check_present(asus);
 	if (err)
 		goto fail_fan_boost_mode;
@@ -3578,6 +3639,7 @@ static int asus_wmi_add(struct platform_device *pdev)
 fail_fan_boost_mode:
 fail_egpu_enable:
 fail_dgpu_disable:
+fail_gpu_mux_mode:
 fail_platform:
 fail_panel_od:
 	kfree(asus);
diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
index a571b47ff362..c023332842a2 100644
--- a/include/linux/platform_data/x86/asus-wmi.h
+++ b/include/linux/platform_data/x86/asus-wmi.h
@@ -98,6 +98,9 @@
 /* dgpu on/off */
 #define ASUS_WMI_DEVID_DGPU		0x00090020
 
+/* gpu mux switch, 0 = dGPU, 1 = Optimus */
+#define ASUS_WMI_DEVID_GPU_MUX 0x00090016
+
 /* DSTS masks */
 #define ASUS_WMI_DSTS_STATUS_BIT	0x00000001
 #define ASUS_WMI_DSTS_UNKNOWN_BIT	0x00000002
-- 
2.37.1