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

From: Luke Jones
Date: Sun Aug 21 2022 - 19:09:25 EST

Hi Mario,

On Mon, Aug 15 2022 at 23:16:12 -0500, Mario Limonciello <mario.limonciello@xxxxxxx> wrote:
On 8/13/22 04:26, Luke D. Jones wrote:
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,

This feel like it should probably export using /sys/class/firmware-attributes. That's exactly how those types of attributes work.

As a bonus, software like fwupd 1.8.4 knows how to manipulate it and you don't need special documentation.

+
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


You can see previous discussion here https://lore.kernel.org/platform-driver-x86/c3bb0989-78d9-c513-1669-75407b2acbac@xxxxxxxxxx/

Below is Hans response verbatim:

> Yes it sounds like a BIOS setting is being toggled from within
> Linux, which would normally be done through the
> "firmware-attributes" class, but all existing "firmware-attributes"
> class drivers allow changing all BIOS setting not just a single
> setting, so using the "firmware-attributes" class here is not really
> appropriate.

Kind regards,
Luke.