From 27e274dbb628027bd6f2d368f317dfd4253a71d3 Mon Sep 17 00:00:00 2001
From: Maximilian Luz <luzmaximilian@gmail.com>
Date: Sat, 13 Feb 2021 16:41:18 +0100
Subject: [PATCH 13/41] platform/surface: Add driver for Surface Book 1 dGPU
switch
Add driver exposing the discrete GPU power-switch of the Microsoft
Surface Book 1 to user-space.
On the Surface Book 1, the dGPU power is controlled via the Surface
System Aggregator Module (SAM). The specific SAM-over-HID command for
this is exposed via ACPI. This module provides a simple driver exposing
the ACPI call via a sysfs parameter to user-space, so that users can
easily power-on/-off the dGPU.
Patchset: surface-sam-over-hid
---
drivers/platform/surface/Kconfig | 7 +
drivers/platform/surface/Makefile | 1 +
.../surface/surfacebook1_dgpu_switch.c | 162 ++++++++++++++++++
3 files changed, 170 insertions(+)
create mode 100644 drivers/platform/surface/surfacebook1_dgpu_switch.c
diff --git a/drivers/platform/surface/Kconfig b/drivers/platform/surface/Kconfig
index b629e82af97c..68656e8f309e 100644
--- a/drivers/platform/surface/Kconfig
+++ b/drivers/platform/surface/Kconfig
@@ -149,6 +149,13 @@ config SURFACE_AGGREGATOR_TABLET_SWITCH
Select M or Y here, if you want to provide tablet-mode switch input
events on the Surface Pro 8, Surface Pro X, and Surface Laptop Studio.
+config SURFACE_BOOK1_DGPU_SWITCH
+ tristate "Surface Book 1 dGPU Switch Driver"
+ depends on SYSFS
+ help
+ This driver provides a sysfs switch to set the power-state of the
+ discrete GPU found on the Microsoft Surface Book 1.
+
config SURFACE_DTX
tristate "Surface DTX (Detachment System) Driver"
depends on SURFACE_AGGREGATOR
diff --git a/drivers/platform/surface/Makefile b/drivers/platform/surface/Makefile
index 53344330939b..7efcd0cdb532 100644
--- a/drivers/platform/surface/Makefile
+++ b/drivers/platform/surface/Makefile
@@ -12,6 +12,7 @@ obj-$(CONFIG_SURFACE_AGGREGATOR_CDEV) += surface_aggregator_cdev.o
obj-$(CONFIG_SURFACE_AGGREGATOR_HUB) += surface_aggregator_hub.o
obj-$(CONFIG_SURFACE_AGGREGATOR_REGISTRY) += surface_aggregator_registry.o
obj-$(CONFIG_SURFACE_AGGREGATOR_TABLET_SWITCH) += surface_aggregator_tabletsw.o
+obj-$(CONFIG_SURFACE_BOOK1_DGPU_SWITCH) += surfacebook1_dgpu_switch.o
obj-$(CONFIG_SURFACE_DTX) += surface_dtx.o
obj-$(CONFIG_SURFACE_GPE) += surface_gpe.o
obj-$(CONFIG_SURFACE_HOTPLUG) += surface_hotplug.o
diff --git a/drivers/platform/surface/surfacebook1_dgpu_switch.c b/drivers/platform/surface/surfacebook1_dgpu_switch.c
new file mode 100644
index 000000000000..8b816ed8f35c
--- /dev/null
+++ b/drivers/platform/surface/surfacebook1_dgpu_switch.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__
+
+
+static const guid_t dgpu_sw_guid = GUID_INIT(0x6fd05c69, 0xcde3, 0x49f4,
+ 0x95, 0xed, 0xab, 0x16, 0x65, 0x49, 0x80, 0x35);
+
+#define DGPUSW_ACPI_PATH_DSM "\\_SB_.PCI0.LPCB.EC0_.VGBI"
+#define DGPUSW_ACPI_PATH_HGON "\\_SB_.PCI0.RP05.HGON"
+#define DGPUSW_ACPI_PATH_HGOF "\\_SB_.PCI0.RP05.HGOF"
+
+
+static int sb1_dgpu_sw_dsmcall(void)
+{
+ union acpi_object *ret;
+ acpi_handle handle;
+ acpi_status status;
+
+ status = acpi_get_handle(NULL, DGPUSW_ACPI_PATH_DSM, &handle);
+ if (status)
+ return -EINVAL;
+
+ ret = acpi_evaluate_dsm_typed(handle, &dgpu_sw_guid, 1, 1, NULL, ACPI_TYPE_BUFFER);
+ if (!ret)
+ return -EINVAL;
+
+ ACPI_FREE(ret);
+ return 0;
+}
+
+static int sb1_dgpu_sw_hgon(void)
+{
+ struct acpi_buffer buf = {ACPI_ALLOCATE_BUFFER, NULL};
+ acpi_status status;
+
+ status = acpi_evaluate_object(NULL, DGPUSW_ACPI_PATH_HGON, NULL, &buf);
+ if (status) {
+ pr_err("failed to run HGON: %d\n", status);
+ return -EINVAL;
+ }
+
+ if (buf.pointer)
+ ACPI_FREE(buf.pointer);
+
+ pr_info("turned-on dGPU via HGON\n");
+ return 0;
+}
+
+static int sb1_dgpu_sw_hgof(void)
+{
+ struct acpi_buffer buf = {ACPI_ALLOCATE_BUFFER, NULL};
+ acpi_status status;
+
+ status = acpi_evaluate_object(NULL, DGPUSW_ACPI_PATH_HGOF, NULL, &buf);
+ if (status) {
+ pr_err("failed to run HGOF: %d\n", status);
+ return -EINVAL;
+ }
+
+ if (buf.pointer)
+ ACPI_FREE(buf.pointer);
+
+ pr_info("turned-off dGPU via HGOF\n");
+ return 0;
+}
+
+
+static ssize_t dgpu_dsmcall_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ int status, value;
+
+ status = kstrtoint(buf, 0, &value);
+ if (status < 0)
+ return status;
+
+ if (value != 1)
+ return -EINVAL;
+
+ status = sb1_dgpu_sw_dsmcall();
+
+ return status < 0 ? status : len;
+}
+
+static ssize_t dgpu_power_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ bool power;
+ int status;
+
+ status = kstrtobool(buf, &power);
+ if (status < 0)
+ return status;
+
+ if (power)
+ status = sb1_dgpu_sw_hgon();
+ else
+ status = sb1_dgpu_sw_hgof();
+
+ return status < 0 ? status : len;
+}
+
+static DEVICE_ATTR_WO(dgpu_dsmcall);
+static DEVICE_ATTR_WO(dgpu_power);
+
+static struct attribute *sb1_dgpu_sw_attrs[] = {
+ &dev_attr_dgpu_dsmcall.attr,
+ &dev_attr_dgpu_power.attr,
+ NULL,
+};
+
+static const struct attribute_group sb1_dgpu_sw_attr_group = {
+ .attrs = sb1_dgpu_sw_attrs,
+};
+
+
+static int sb1_dgpu_sw_probe(struct platform_device *pdev)
+{
+ return sysfs_create_group(&pdev->dev.kobj, &sb1_dgpu_sw_attr_group);
+}
+
+static int sb1_dgpu_sw_remove(struct platform_device *pdev)
+{
+ sysfs_remove_group(&pdev->dev.kobj, &sb1_dgpu_sw_attr_group);
+ return 0;
+}
+
+/*
+ * The dGPU power seems to be actually handled by MSHW0040. However, that is
+ * also the power-/volume-button device with a mainline driver. So let's use
+ * MSHW0041 instead for now, which seems to be the LTCH (latch/DTX) device.
+ */
+static const struct acpi_device_id sb1_dgpu_sw_match[] = {
+ { "MSHW0041", },
+ { },
+};
+MODULE_DEVICE_TABLE(acpi, sb1_dgpu_sw_match);
+
+static struct platform_driver sb1_dgpu_sw = {
+ .probe = sb1_dgpu_sw_probe,
+ .remove = sb1_dgpu_sw_remove,
+ .driver = {
+ .name = "surfacebook1_dgpu_switch",
+ .acpi_match_table = sb1_dgpu_sw_match,
+ .probe_type = PROBE_PREFER_ASYNCHRONOUS,
+ },
+};
+module_platform_driver(sb1_dgpu_sw);
+
+MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
+MODULE_DESCRIPTION("Discrete GPU Power-Switch for Surface Book 1");
+MODULE_LICENSE("GPL");
--
2.41.0
