[PATCH v3 6/6] asus-wmi: Support the hardware GPU MUX on some laptops

["Luke D. Jones" <luke@ljones.dev>]

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@ljones.dev>
---
 .../ABI/testing/sysfs-platform-asus-wmi       |  9 ++
 drivers/platform/x86/asus-wmi.c               | 91 +++++++++++++++++++
 include/linux/platform_data/x86/asus-wmi.h    |  3 +
 3 files changed, 103 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-platform-asus-wmi b/Documentation/ABI/testing/sysfs-platform-asus-wmi
index 541dbfbbbb26..d483bc3cb2e6 100644
--- a/Documentation/ABI/testing/sysfs-platform-asus-wmi
+++ b/Documentation/ABI/testing/sysfs-platform-asus-wmi
@@ -67,6 +67,15 @@ Description:
 			* 0 - Disable,
 			* 1 - Enable,
 
+What:		/sys/devices/platform/<platform>/gpu_mux_mode
+Date:		Aug 2022
+KernelVersion:	6.0
+Contact:	"Luke Jones" <luke@ljones.dev>
+Description:
+		Switch the GPU used by the hardware MUX:
+			* 0 - Dedicated GPU,
+			* 1 - Optimus mode,
+
 What:		/sys/devices/platform/<platform>/panel_od
 Date:		Aug 2022
 KernelVersion:	5.17
diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 78f1f3af1b12..c5fa21370481 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -246,6 +246,9 @@ struct asus_wmi {
 	bool dgpu_disable_available;
 	bool dgpu_disable;
 
+	bool gpu_mux_mode_available;
+	bool gpu_mux_mode;
+
 	bool keyboard_rgb_state_available;
 	bool keyboard_rgb_mode_available;
 	struct keyboard_rgb_led keyboard_rgb_led;
@@ -750,6 +753,86 @@ 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)
+{
+	u32 result;
+	int err;
+
+	asus->gpu_mux_mode_available = false;
+
+	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_GPU_MUX, &result);
+	if (err) {
+		if (err == -ENODEV)
+			return 0;
+		return err;
+	}
+
+	if (result & ASUS_WMI_DSTS_PRESENCE_BIT) {
+		asus->gpu_mux_mode_available = true;
+		asus->gpu_mux_mode = result & ASUS_WMI_DSTS_STATUS_BIT;
+	}
+
+	return 0;
+}
+
+static int gpu_mux_mode_write(struct asus_wmi *asus)
+{
+	u32 retval;
+	u8 value;
+	int err;
+
+	/* Don't rely on type conversion */
+	value = asus->gpu_mux_mode ? 1 : 0;
+
+	err = asus_wmi_set_devstate(ASUS_WMI_DEVID_GPU_MUX, value, &retval);
+	if (err) {
+		pr_warn("Failed to set dGPU-only mode: %d\n", err);
+		return err;
+	}
+
+	if (retval > 1) {
+		pr_warn("Failed to set dGPU-only mode (retval): 0x%x\n", retval);
+		return -EIO;
+	}
+
+	sysfs_notify(&asus->platform_device->dev.kobj, NULL, "gpu_mux_mode");
+
+	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);
+	u8 mode = asus->gpu_mux_mode;
+
+	return sysfs_emit(buf, "%d\n", mode);
+}
+
+static ssize_t gpu_mux_mode_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	bool optimus;
+	int result;
+
+	struct asus_wmi *asus = dev_get_drvdata(dev);
+
+	result = kstrtobool(buf, &optimus);
+	if (result)
+		return result;
+
+	asus->gpu_mux_mode = optimus;
+
+	result = gpu_mux_mode_write(asus);
+	if (result)
+		return result;
+
+	return count;
+}
+static DEVICE_ATTR_RW(gpu_mux_mode);
+
 /* TUF Laptop Keyboard RGB Modes **********************************************/
 static int keyboard_rgb_check_present(struct asus_wmi *asus)
 {
@@ -3496,6 +3579,7 @@ 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_keyboard_rgb_save.attr,
 	&dev_attr_keyboard_rgb_mode.attr,
 	&dev_attr_keyboard_rgb_speed.attr,
@@ -3531,6 +3615,8 @@ 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_keyboard_rgb_save.attr)
 		ok = asus->keyboard_rgb_mode_available;
 	else if (attr == &dev_attr_keyboard_rgb_mode.attr)
@@ -3810,6 +3896,10 @@ 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 = keyboard_rgb_check_present(asus);
 	if (err)
 		goto fail_keyboard_rgb_mode;
@@ -3932,6 +4022,7 @@ static int asus_wmi_add(struct platform_device *pdev)
 fail_fan_boost_mode:
 fail_egpu_enable:
 fail_dgpu_disable:
+fail_gpu_mux_mode:
 fail_keyboard_rgb_mode:
 fail_keyboard_rgb_state:
 fail_platform:
diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
index b5c966798ef8..3faeb98f6ea9 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
+
 /* TUF laptop RGB control */
 #define ASUS_WMI_DEVID_TUF_RGB_MODE	0x00100056
 /* TUF laptop RGB state control */
-- 
2.37.1