Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1078 insertions, 0 deletions

diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
new file mode 100644
index 000000000..365e6ddbe
--- /dev/null
+++ b/drivers/gpu/vga/vga_switcheroo.c
@@ -0,0 +1,1078 @@
+/*
+ * vga_switcheroo.c - Support for laptop with dual GPU using one set of outputs
+ *
+ * Copyright (c) 2010 Red Hat Inc.
+ * Author : Dave Airlie <airlied@redhat.com>
+ *
+ * Copyright (c) 2015 Lukas Wunner <lukas@wunner.de>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#define pr_fmt(fmt) "vga_switcheroo: " fmt
+
+#include <linux/apple-gmux.h>
+#include <linux/console.h>
+#include <linux/debugfs.h>
+#include <linux/fb.h>
+#include <linux/fs.h>
+#include <linux/fbcon.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_runtime.h>
+#include <linux/seq_file.h>
+#include <linux/uaccess.h>
+#include <linux/vgaarb.h>
+#include <linux/vga_switcheroo.h>
+
+/**
+ * DOC: Overview
+ *
+ * vga_switcheroo is the Linux subsystem for laptop hybrid graphics.
+ * These come in two flavors:
+ *
+ * * muxed: Dual GPUs with a multiplexer chip to switch outputs between GPUs.
+ * * muxless: Dual GPUs but only one of them is connected to outputs.
+ *   The other one is merely used to offload rendering, its results
+ *   are copied over PCIe into the framebuffer. On Linux this is
+ *   supported with DRI PRIME.
+ *
+ * Hybrid graphics started to appear in the late Naughties and were initially
+ * all muxed. Newer laptops moved to a muxless architecture for cost reasons.
+ * A notable exception is the MacBook Pro which continues to use a mux.
+ * Muxes come with varying capabilities: Some switch only the panel, others
+ * can also switch external displays. Some switch all display pins at once
+ * while others can switch just the DDC lines. (To allow EDID probing
+ * for the inactive GPU.) Also, muxes are often used to cut power to the
+ * discrete GPU while it is not used.
+ *
+ * DRM drivers register GPUs with vga_switcheroo, these are henceforth called
+ * clients. The mux is called the handler. Muxless machines also register a
+ * handler to control the power state of the discrete GPU, its ->switchto
+ * callback is a no-op for obvious reasons. The discrete GPU is often equipped
+ * with an HDA controller for the HDMI/DP audio signal, this will also
+ * register as a client so that vga_switcheroo can take care of the correct
+ * suspend/resume order when changing the discrete GPU's power state. In total
+ * there can thus be up to three clients: Two vga clients (GPUs) and one audio
+ * client (on the discrete GPU). The code is mostly prepared to support
+ * machines with more than two GPUs should they become available.
+ *
+ * The GPU to which the outputs are currently switched is called the
+ * active client in vga_switcheroo parlance. The GPU not in use is the
+ * inactive client. When the inactive client's DRM driver is loaded,
+ * it will be unable to probe the panel's EDID and hence depends on
+ * VBIOS to provide its display modes. If the VBIOS modes are bogus or
+ * if there is no VBIOS at all (which is common on the MacBook Pro),
+ * a client may alternatively request that the DDC lines are temporarily
+ * switched to it, provided that the handler supports this. Switching
+ * only the DDC lines and not the entire output avoids unnecessary
+ * flickering.
+ */
+
+/**
+ * struct vga_switcheroo_client - registered client
+ * @pdev: client pci device
+ * @fb_info: framebuffer to which console is remapped on switching
+ * @pwr_state: current power state if manual power control is used.
+ *	For driver power control, call vga_switcheroo_pwr_state().
+ * @ops: client callbacks
+ * @id: client identifier. Determining the id requires the handler,
+ *	so gpus are initially assigned VGA_SWITCHEROO_UNKNOWN_ID
+ *	and later given their true id in vga_switcheroo_enable()
+ * @active: whether the outputs are currently switched to this client
+ * @driver_power_control: whether power state is controlled by the driver's
+ *	runtime pm. If true, writing ON and OFF to the vga_switcheroo debugfs
+ *	interface is a no-op so as not to interfere with runtime pm
+ * @list: client list
+ * @vga_dev: pci device, indicate which GPU is bound to current audio client
+ *
+ * Registered client. A client can be either a GPU or an audio device on a GPU.
+ * For audio clients, the @fb_info and @active members are bogus. For GPU
+ * clients, the @vga_dev is bogus.
+ */
+struct vga_switcheroo_client {
+	struct pci_dev *pdev;
+	struct fb_info *fb_info;
+	enum vga_switcheroo_state pwr_state;
+	const struct vga_switcheroo_client_ops *ops;
+	enum vga_switcheroo_client_id id;
+	bool active;
+	bool driver_power_control;
+	struct list_head list;
+	struct pci_dev *vga_dev;
+};
+
+/*
+ * protects access to struct vgasr_priv
+ */
+static DEFINE_MUTEX(vgasr_mutex);
+
+/**
+ * struct vgasr_priv - vga_switcheroo private data
+ * @active: whether vga_switcheroo is enabled.
+ *	Prerequisite is the registration of two GPUs and a handler
+ * @delayed_switch_active: whether a delayed switch is pending
+ * @delayed_client_id: client to which a delayed switch is pending
+ * @debugfs_root: directory for vga_switcheroo debugfs interface
+ * @registered_clients: number of registered GPUs
+ *	(counting only vga clients, not audio clients)
+ * @clients: list of registered clients
+ * @handler: registered handler
+ * @handler_flags: flags of registered handler
+ * @mux_hw_lock: protects mux state
+ *	(in particular while DDC lines are temporarily switched)
+ * @old_ddc_owner: client to which DDC lines will be switched back on unlock
+ *
+ * vga_switcheroo private data. Currently only one vga_switcheroo instance
+ * per system is supported.
+ */
+struct vgasr_priv {
+	bool active;
+	bool delayed_switch_active;
+	enum vga_switcheroo_client_id delayed_client_id;
+
+	struct dentry *debugfs_root;
+
+	int registered_clients;
+	struct list_head clients;
+
+	const struct vga_switcheroo_handler *handler;
+	enum vga_switcheroo_handler_flags_t handler_flags;
+	struct mutex mux_hw_lock;
+	int old_ddc_owner;
+};
+
+#define ID_BIT_AUDIO		0x100
+#define client_is_audio(c)		((c)->id & ID_BIT_AUDIO)
+#define client_is_vga(c)		(!client_is_audio(c))
+#define client_id(c)		((c)->id & ~ID_BIT_AUDIO)
+
+static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv);
+static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv);
+
+/* only one switcheroo per system */
+static struct vgasr_priv vgasr_priv = {
+	.clients = LIST_HEAD_INIT(vgasr_priv.clients),
+	.mux_hw_lock = __MUTEX_INITIALIZER(vgasr_priv.mux_hw_lock),
+};
+
+static bool vga_switcheroo_ready(void)
+{
+	/* we're ready if we get two clients + handler */
+	return !vgasr_priv.active &&
+	       vgasr_priv.registered_clients == 2 && vgasr_priv.handler;
+}
+
+static void vga_switcheroo_enable(void)
+{
+	int ret;
+	struct vga_switcheroo_client *client;
+
+	/* call the handler to init */
+	if (vgasr_priv.handler->init)
+		vgasr_priv.handler->init();
+
+	list_for_each_entry(client, &vgasr_priv.clients, list) {
+		if (!client_is_vga(client) ||
+		     client_id(client) != VGA_SWITCHEROO_UNKNOWN_ID)
+			continue;
+
+		ret = vgasr_priv.handler->get_client_id(client->pdev);
+		if (ret < 0)
+			return;
+
+		client->id = ret;
+	}
+
+	list_for_each_entry(client, &vgasr_priv.clients, list) {
+		if (!client_is_audio(client) ||
+		     client_id(client) != VGA_SWITCHEROO_UNKNOWN_ID)
+			continue;
+
+		ret = vgasr_priv.handler->get_client_id(client->vga_dev);
+		if (ret < 0)
+			return;
+
+		client->id = ret | ID_BIT_AUDIO;
+		if (client->ops->gpu_bound)
+			client->ops->gpu_bound(client->pdev, ret);
+	}
+
+	vga_switcheroo_debugfs_init(&vgasr_priv);
+	vgasr_priv.active = true;
+}
+
+/**
+ * vga_switcheroo_register_handler() - register handler
+ * @handler: handler callbacks
+ * @handler_flags: handler flags
+ *
+ * Register handler. Enable vga_switcheroo if two vga clients have already
+ * registered.
+ *
+ * Return: 0 on success, -EINVAL if a handler was already registered.
+ */
+int vga_switcheroo_register_handler(
+			  const struct vga_switcheroo_handler *handler,
+			  enum vga_switcheroo_handler_flags_t handler_flags)
+{
+	mutex_lock(&vgasr_mutex);
+	if (vgasr_priv.handler) {
+		mutex_unlock(&vgasr_mutex);
+		return -EINVAL;
+	}
+
+	vgasr_priv.handler = handler;
+	vgasr_priv.handler_flags = handler_flags;
+	if (vga_switcheroo_ready()) {
+		pr_info("enabled\n");
+		vga_switcheroo_enable();
+	}
+	mutex_unlock(&vgasr_mutex);
+	return 0;
+}
+EXPORT_SYMBOL(vga_switcheroo_register_handler);
+
+/**
+ * vga_switcheroo_unregister_handler() - unregister handler
+ *
+ * Unregister handler. Disable vga_switcheroo.
+ */
+void vga_switcheroo_unregister_handler(void)
+{
+	mutex_lock(&vgasr_mutex);
+	mutex_lock(&vgasr_priv.mux_hw_lock);
+	vgasr_priv.handler_flags = 0;
+	vgasr_priv.handler = NULL;
+	if (vgasr_priv.active) {
+		pr_info("disabled\n");
+		vga_switcheroo_debugfs_fini(&vgasr_priv);
+		vgasr_priv.active = false;
+	}
+	mutex_unlock(&vgasr_priv.mux_hw_lock);
+	mutex_unlock(&vgasr_mutex);
+}
+EXPORT_SYMBOL(vga_switcheroo_unregister_handler);
+
+/**
+ * vga_switcheroo_handler_flags() - obtain handler flags
+ *
+ * Helper for clients to obtain the handler flags bitmask.
+ *
+ * Return: Handler flags. A value of 0 means that no handler is registered
+ * or that the handler has no special capabilities.
+ */
+enum vga_switcheroo_handler_flags_t vga_switcheroo_handler_flags(void)
+{
+	return vgasr_priv.handler_flags;
+}
+EXPORT_SYMBOL(vga_switcheroo_handler_flags);
+
+static int register_client(struct pci_dev *pdev,
+			   const struct vga_switcheroo_client_ops *ops,
+			   enum vga_switcheroo_client_id id,
+			   struct pci_dev *vga_dev,
+			   bool active,
+			   bool driver_power_control)
+{
+	struct vga_switcheroo_client *client;
+
+	client = kzalloc(sizeof(*client), GFP_KERNEL);
+	if (!client)
+		return -ENOMEM;
+
+	client->pwr_state = VGA_SWITCHEROO_ON;
+	client->pdev = pdev;
+	client->ops = ops;
+	client->id = id;
+	client->active = active;
+	client->driver_power_control = driver_power_control;
+	client->vga_dev = vga_dev;
+
+	mutex_lock(&vgasr_mutex);
+	list_add_tail(&client->list, &vgasr_priv.clients);
+	if (client_is_vga(client))
+		vgasr_priv.registered_clients++;
+
+	if (vga_switcheroo_ready()) {
+		pr_info("enabled\n");
+		vga_switcheroo_enable();
+	}
+	mutex_unlock(&vgasr_mutex);
+	return 0;
+}
+
+/**
+ * vga_switcheroo_register_client - register vga client
+ * @pdev: client pci device
+ * @ops: client callbacks
+ * @driver_power_control: whether power state is controlled by the driver's
+ *	runtime pm
+ *
+ * Register vga client (GPU). Enable vga_switcheroo if another GPU and a
+ * handler have already registered. The power state of the client is assumed
+ * to be ON. Beforehand, vga_switcheroo_client_probe_defer() shall be called
+ * to ensure that all prerequisites are met.
+ *
+ * Return: 0 on success, -ENOMEM on memory allocation error.
+ */
+int vga_switcheroo_register_client(struct pci_dev *pdev,
+				   const struct vga_switcheroo_client_ops *ops,
+				   bool driver_power_control)
+{
+	return register_client(pdev, ops, VGA_SWITCHEROO_UNKNOWN_ID, NULL,
+			       pdev == vga_default_device(),
+			       driver_power_control);
+}
+EXPORT_SYMBOL(vga_switcheroo_register_client);
+
+/**
+ * vga_switcheroo_register_audio_client - register audio client
+ * @pdev: client pci device
+ * @ops: client callbacks
+ * @vga_dev:  pci device which is bound to current audio client
+ *
+ * Register audio client (audio device on a GPU). The client is assumed
+ * to use runtime PM. Beforehand, vga_switcheroo_client_probe_defer()
+ * shall be called to ensure that all prerequisites are met.
+ *
+ * Return: 0 on success, -ENOMEM on memory allocation error, -EINVAL on getting
+ * client id error.
+ */
+int vga_switcheroo_register_audio_client(struct pci_dev *pdev,
+			const struct vga_switcheroo_client_ops *ops,
+			struct pci_dev *vga_dev)
+{
+	enum vga_switcheroo_client_id id = VGA_SWITCHEROO_UNKNOWN_ID;
+
+	/*
+	 * if vga_switcheroo has enabled, that mean two GPU clients and also
+	 * handler are registered. Get audio client id from bound GPU client
+	 * id directly, otherwise, set it as VGA_SWITCHEROO_UNKNOWN_ID,
+	 * it will set to correct id in later when vga_switcheroo_enable()
+	 * is called.
+	 */
+	mutex_lock(&vgasr_mutex);
+	if (vgasr_priv.active) {
+		id = vgasr_priv.handler->get_client_id(vga_dev);
+		if (id < 0) {
+			mutex_unlock(&vgasr_mutex);
+			return -EINVAL;
+		}
+		/* notify if GPU has been already bound */
+		if (ops->gpu_bound)
+			ops->gpu_bound(pdev, id);
+	}
+	mutex_unlock(&vgasr_mutex);
+
+	return register_client(pdev, ops, id | ID_BIT_AUDIO, vga_dev,
+			       false, true);
+}
+EXPORT_SYMBOL(vga_switcheroo_register_audio_client);
+
+static struct vga_switcheroo_client *
+find_client_from_pci(struct list_head *head, struct pci_dev *pdev)
+{
+	struct vga_switcheroo_client *client;
+
+	list_for_each_entry(client, head, list)
+		if (client->pdev == pdev)
+			return client;
+	return NULL;
+}
+
+static struct vga_switcheroo_client *
+find_client_from_id(struct list_head *head,
+		    enum vga_switcheroo_client_id client_id)
+{
+	struct vga_switcheroo_client *client;
+
+	list_for_each_entry(client, head, list)
+		if (client->id == client_id)
+			return client;
+	return NULL;
+}
+
+static struct vga_switcheroo_client *
+find_active_client(struct list_head *head)
+{
+	struct vga_switcheroo_client *client;
+
+	list_for_each_entry(client, head, list)
+		if (client->active)
+			return client;
+	return NULL;
+}
+
+/**
+ * vga_switcheroo_client_probe_defer() - whether to defer probing a given client
+ * @pdev: client pci device
+ *
+ * Determine whether any prerequisites are not fulfilled to probe a given
+ * client. Drivers shall invoke this early on in their ->probe callback
+ * and return %-EPROBE_DEFER if it evaluates to %true. Thou shalt not
+ * register the client ere thou hast called this.
+ *
+ * Return: %true if probing should be deferred, otherwise %false.
+ */
+bool vga_switcheroo_client_probe_defer(struct pci_dev *pdev)
+{
+	if ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY) {
+		/*
+		 * apple-gmux is needed on pre-retina MacBook Pro
+		 * to probe the panel if pdev is the inactive GPU.
+		 */
+		if (apple_gmux_present() && pdev != vga_default_device() &&
+		    !vgasr_priv.handler_flags)
+			return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL(vga_switcheroo_client_probe_defer);
+
+static enum vga_switcheroo_state
+vga_switcheroo_pwr_state(struct vga_switcheroo_client *client)
+{
+	if (client->driver_power_control)
+		if (pm_runtime_enabled(&client->pdev->dev) &&
+		    pm_runtime_active(&client->pdev->dev))
+			return VGA_SWITCHEROO_ON;
+		else
+			return VGA_SWITCHEROO_OFF;
+	else
+		return client->pwr_state;
+}
+
+/**
+ * vga_switcheroo_get_client_state() - obtain power state of a given client
+ * @pdev: client pci device
+ *
+ * Obtain power state of a given client as seen from vga_switcheroo.
+ * The function is only called from hda_intel.c.
+ *
+ * Return: Power state.
+ */
+enum vga_switcheroo_state vga_switcheroo_get_client_state(struct pci_dev *pdev)
+{
+	struct vga_switcheroo_client *client;
+	enum vga_switcheroo_state ret;
+
+	mutex_lock(&vgasr_mutex);
+	client = find_client_from_pci(&vgasr_priv.clients, pdev);
+	if (!client)
+		ret = VGA_SWITCHEROO_NOT_FOUND;
+	else
+		ret = vga_switcheroo_pwr_state(client);
+	mutex_unlock(&vgasr_mutex);
+	return ret;
+}
+EXPORT_SYMBOL(vga_switcheroo_get_client_state);
+
+/**
+ * vga_switcheroo_unregister_client() - unregister client
+ * @pdev: client pci device
+ *
+ * Unregister client. Disable vga_switcheroo if this is a vga client (GPU).
+ */
+void vga_switcheroo_unregister_client(struct pci_dev *pdev)
+{
+	struct vga_switcheroo_client *client;
+
+	mutex_lock(&vgasr_mutex);
+	client = find_client_from_pci(&vgasr_priv.clients, pdev);
+	if (client) {
+		if (client_is_vga(client))
+			vgasr_priv.registered_clients--;
+		list_del(&client->list);
+		kfree(client);
+	}
+	if (vgasr_priv.active && vgasr_priv.registered_clients < 2) {
+		pr_info("disabled\n");
+		vga_switcheroo_debugfs_fini(&vgasr_priv);
+		vgasr_priv.active = false;
+	}
+	mutex_unlock(&vgasr_mutex);
+}
+EXPORT_SYMBOL(vga_switcheroo_unregister_client);
+
+/**
+ * vga_switcheroo_client_fb_set() - set framebuffer of a given client
+ * @pdev: client pci device
+ * @info: framebuffer
+ *
+ * Set framebuffer of a given client. The console will be remapped to this
+ * on switching.
+ */
+void vga_switcheroo_client_fb_set(struct pci_dev *pdev,
+				 struct fb_info *info)
+{
+	struct vga_switcheroo_client *client;
+
+	mutex_lock(&vgasr_mutex);
+	client = find_client_from_pci(&vgasr_priv.clients, pdev);
+	if (client)
+		client->fb_info = info;
+	mutex_unlock(&vgasr_mutex);
+}
+EXPORT_SYMBOL(vga_switcheroo_client_fb_set);
+
+/**
+ * vga_switcheroo_lock_ddc() - temporarily switch DDC lines to a given client
+ * @pdev: client pci device
+ *
+ * Temporarily switch DDC lines to the client identified by @pdev
+ * (but leave the outputs otherwise switched to where they are).
+ * This allows the inactive client to probe EDID. The DDC lines must
+ * afterwards be switched back by calling vga_switcheroo_unlock_ddc(),
+ * even if this function returns an error.
+ *
+ * Return: Previous DDC owner on success or a negative int on error.
+ * Specifically, %-ENODEV if no handler has registered or if the handler
+ * does not support switching the DDC lines. Also, a negative value
+ * returned by the handler is propagated back to the caller.
+ * The return value has merely an informational purpose for any caller
+ * which might be interested in it. It is acceptable to ignore the return
+ * value and simply rely on the result of the subsequent EDID probe,
+ * which will be %NULL if DDC switching failed.
+ */
+int vga_switcheroo_lock_ddc(struct pci_dev *pdev)
+{
+	enum vga_switcheroo_client_id id;
+
+	mutex_lock(&vgasr_priv.mux_hw_lock);
+	if (!vgasr_priv.handler || !vgasr_priv.handler->switch_ddc) {
+		vgasr_priv.old_ddc_owner = -ENODEV;
+		return -ENODEV;
+	}
+
+	id = vgasr_priv.handler->get_client_id(pdev);
+	vgasr_priv.old_ddc_owner = vgasr_priv.handler->switch_ddc(id);
+	return vgasr_priv.old_ddc_owner;
+}
+EXPORT_SYMBOL(vga_switcheroo_lock_ddc);
+
+/**
+ * vga_switcheroo_unlock_ddc() - switch DDC lines back to previous owner
+ * @pdev: client pci device
+ *
+ * Switch DDC lines back to the previous owner after calling
+ * vga_switcheroo_lock_ddc(). This must be called even if
+ * vga_switcheroo_lock_ddc() returned an error.
+ *
+ * Return: Previous DDC owner on success (i.e. the client identifier of @pdev)
+ * or a negative int on error.
+ * Specifically, %-ENODEV if no handler has registered or if the handler
+ * does not support switching the DDC lines. Also, a negative value
+ * returned by the handler is propagated back to the caller.
+ * Finally, invoking this function without calling vga_switcheroo_lock_ddc()
+ * first is not allowed and will result in %-EINVAL.
+ */
+int vga_switcheroo_unlock_ddc(struct pci_dev *pdev)
+{
+	enum vga_switcheroo_client_id id;
+	int ret = vgasr_priv.old_ddc_owner;
+
+	if (WARN_ON_ONCE(!mutex_is_locked(&vgasr_priv.mux_hw_lock)))
+		return -EINVAL;
+
+	if (vgasr_priv.old_ddc_owner >= 0) {
+		id = vgasr_priv.handler->get_client_id(pdev);
+		if (vgasr_priv.old_ddc_owner != id)
+			ret = vgasr_priv.handler->switch_ddc(
+						     vgasr_priv.old_ddc_owner);
+	}
+	mutex_unlock(&vgasr_priv.mux_hw_lock);
+	return ret;
+}
+EXPORT_SYMBOL(vga_switcheroo_unlock_ddc);
+
+/**
+ * DOC: Manual switching and manual power control
+ *
+ * In this mode of use, the file /sys/kernel/debug/vgaswitcheroo/switch
+ * can be read to retrieve the current vga_switcheroo state and commands
+ * can be written to it to change the state. The file appears as soon as
+ * two GPU drivers and one handler have registered with vga_switcheroo.
+ * The following commands are understood:
+ *
+ * * OFF: Power off the device not in use.
+ * * ON: Power on the device not in use.
+ * * IGD: Switch to the integrated graphics device.
+ *   Power on the integrated GPU if necessary, power off the discrete GPU.
+ *   Prerequisite is that no user space processes (e.g. Xorg, alsactl)
+ *   have opened device files of the GPUs or the audio client. If the
+ *   switch fails, the user may invoke lsof(8) or fuser(1) on /dev/dri/
+ *   and /dev/snd/controlC1 to identify processes blocking the switch.
+ * * DIS: Switch to the discrete graphics device.
+ * * DIGD: Delayed switch to the integrated graphics device.
+ *   This will perform the switch once the last user space process has
+ *   closed the device files of the GPUs and the audio client.
+ * * DDIS: Delayed switch to the discrete graphics device.
+ * * MIGD: Mux-only switch to the integrated graphics device.
+ *   Does not remap console or change the power state of either gpu.
+ *   If the integrated GPU is currently off, the screen will turn black.
+ *   If it is on, the screen will show whatever happens to be in VRAM.
+ *   Either way, the user has to blindly enter the command to switch back.
+ * * MDIS: Mux-only switch to the discrete graphics device.
+ *
+ * For GPUs whose power state is controlled by the driver's runtime pm,
+ * the ON and OFF commands are a no-op (see next section).
+ *
+ * For muxless machines, the IGD/DIS, DIGD/DDIS and MIGD/MDIS commands
+ * should not be used.
+ */
+
+static int vga_switcheroo_show(struct seq_file *m, void *v)
+{
+	struct vga_switcheroo_client *client;
+	int i = 0;
+
+	mutex_lock(&vgasr_mutex);
+	list_for_each_entry(client, &vgasr_priv.clients, list) {
+		seq_printf(m, "%d:%s%s:%c:%s%s:%s\n", i,
+			   client_id(client) == VGA_SWITCHEROO_DIS ? "DIS" :
+								     "IGD",
+			   client_is_vga(client) ? "" : "-Audio",
+			   client->active ? '+' : ' ',
+			   client->driver_power_control ? "Dyn" : "",
+			   vga_switcheroo_pwr_state(client) ? "Pwr" : "Off",
+			   pci_name(client->pdev));
+		i++;
+	}
+	mutex_unlock(&vgasr_mutex);
+	return 0;
+}
+
+static int vga_switcheroo_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, vga_switcheroo_show, NULL);
+}
+
+static int vga_switchon(struct vga_switcheroo_client *client)
+{
+	if (client->driver_power_control)
+		return 0;
+	if (vgasr_priv.handler->power_state)
+		vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_ON);
+	/* call the driver callback to turn on device */
+	client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_ON);
+	client->pwr_state = VGA_SWITCHEROO_ON;
+	return 0;
+}
+
+static int vga_switchoff(struct vga_switcheroo_client *client)
+{
+	if (client->driver_power_control)
+		return 0;
+	/* call the driver callback to turn off device */
+	client->ops->set_gpu_state(client->pdev, VGA_SWITCHEROO_OFF);
+	if (vgasr_priv.handler->power_state)
+		vgasr_priv.handler->power_state(client->id, VGA_SWITCHEROO_OFF);
+	client->pwr_state = VGA_SWITCHEROO_OFF;
+	return 0;
+}
+
+static void set_audio_state(enum vga_switcheroo_client_id id,
+			    enum vga_switcheroo_state state)
+{
+	struct vga_switcheroo_client *client;
+
+	client = find_client_from_id(&vgasr_priv.clients, id | ID_BIT_AUDIO);
+	if (client)
+		client->ops->set_gpu_state(client->pdev, state);
+}
+
+/* stage one happens before delay */
+static int vga_switchto_stage1(struct vga_switcheroo_client *new_client)
+{
+	struct vga_switcheroo_client *active;
+
+	active = find_active_client(&vgasr_priv.clients);
+	if (!active)
+		return 0;
+
+	if (vga_switcheroo_pwr_state(new_client) == VGA_SWITCHEROO_OFF)
+		vga_switchon(new_client);
+
+	vga_set_default_device(new_client->pdev);
+	return 0;
+}
+
+/* post delay */
+static int vga_switchto_stage2(struct vga_switcheroo_client *new_client)
+{
+	int ret;
+	struct vga_switcheroo_client *active;
+
+	active = find_active_client(&vgasr_priv.clients);
+	if (!active)
+		return 0;
+
+	active->active = false;
+
+	/* let HDA controller autosuspend if GPU uses driver power control */
+	if (!active->driver_power_control)
+		set_audio_state(active->id, VGA_SWITCHEROO_OFF);
+
+	if (new_client->fb_info)
+		fbcon_remap_all(new_client->fb_info);
+
+	mutex_lock(&vgasr_priv.mux_hw_lock);
+	ret = vgasr_priv.handler->switchto(new_client->id);
+	mutex_unlock(&vgasr_priv.mux_hw_lock);
+	if (ret)
+		return ret;
+
+	if (new_client->ops->reprobe)
+		new_client->ops->reprobe(new_client->pdev);
+
+	if (vga_switcheroo_pwr_state(active) == VGA_SWITCHEROO_ON)
+		vga_switchoff(active);
+
+	/* let HDA controller autoresume if GPU uses driver power control */
+	if (!new_client->driver_power_control)
+		set_audio_state(new_client->id, VGA_SWITCHEROO_ON);
+
+	new_client->active = true;
+	return 0;
+}
+
+static bool check_can_switch(void)
+{
+	struct vga_switcheroo_client *client;
+
+	list_for_each_entry(client, &vgasr_priv.clients, list) {
+		if (!client->ops->can_switch(client->pdev)) {
+			pr_err("client %x refused switch\n", client->id);
+			return false;
+		}
+	}
+	return true;
+}
+
+static ssize_t
+vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
+			     size_t cnt, loff_t *ppos)
+{
+	char usercmd[64];
+	int ret;
+	bool delay = false, can_switch;
+	bool just_mux = false;
+	enum vga_switcheroo_client_id client_id = VGA_SWITCHEROO_UNKNOWN_ID;
+	struct vga_switcheroo_client *client = NULL;
+
+	if (cnt > 63)
+		cnt = 63;
+
+	if (copy_from_user(usercmd, ubuf, cnt))
+		return -EFAULT;
+
+	mutex_lock(&vgasr_mutex);
+
+	if (!vgasr_priv.active) {
+		cnt = -EINVAL;
+		goto out;
+	}
+
+	/* pwr off the device not in use */
+	if (strncmp(usercmd, "OFF", 3) == 0) {
+		list_for_each_entry(client, &vgasr_priv.clients, list) {
+			if (client->active || client_is_audio(client))
+				continue;
+			if (client->driver_power_control)
+				continue;
+			set_audio_state(client->id, VGA_SWITCHEROO_OFF);
+			if (client->pwr_state == VGA_SWITCHEROO_ON)
+				vga_switchoff(client);
+		}
+		goto out;
+	}
+	/* pwr on the device not in use */
+	if (strncmp(usercmd, "ON", 2) == 0) {
+		list_for_each_entry(client, &vgasr_priv.clients, list) {
+			if (client->active || client_is_audio(client))
+				continue;
+			if (client->driver_power_control)
+				continue;
+			if (client->pwr_state == VGA_SWITCHEROO_OFF)
+				vga_switchon(client);
+			set_audio_state(client->id, VGA_SWITCHEROO_ON);
+		}
+		goto out;
+	}
+
+	/* request a delayed switch - test can we switch now */
+	if (strncmp(usercmd, "DIGD", 4) == 0) {
+		client_id = VGA_SWITCHEROO_IGD;
+		delay = true;
+	}
+
+	if (strncmp(usercmd, "DDIS", 4) == 0) {
+		client_id = VGA_SWITCHEROO_DIS;
+		delay = true;
+	}
+
+	if (strncmp(usercmd, "IGD", 3) == 0)
+		client_id = VGA_SWITCHEROO_IGD;
+
+	if (strncmp(usercmd, "DIS", 3) == 0)
+		client_id = VGA_SWITCHEROO_DIS;
+
+	if (strncmp(usercmd, "MIGD", 4) == 0) {
+		just_mux = true;
+		client_id = VGA_SWITCHEROO_IGD;
+	}
+	if (strncmp(usercmd, "MDIS", 4) == 0) {
+		just_mux = true;
+		client_id = VGA_SWITCHEROO_DIS;
+	}
+
+	if (client_id == VGA_SWITCHEROO_UNKNOWN_ID)
+		goto out;
+	client = find_client_from_id(&vgasr_priv.clients, client_id);
+	if (!client)
+		goto out;
+
+	vgasr_priv.delayed_switch_active = false;
+
+	if (just_mux) {
+		mutex_lock(&vgasr_priv.mux_hw_lock);
+		ret = vgasr_priv.handler->switchto(client_id);
+		mutex_unlock(&vgasr_priv.mux_hw_lock);
+		goto out;
+	}
+
+	if (client->active)
+		goto out;
+
+	/* okay we want a switch - test if devices are willing to switch */
+	can_switch = check_can_switch();
+
+	if (can_switch == false && delay == false)
+		goto out;
+
+	if (can_switch) {
+		ret = vga_switchto_stage1(client);
+		if (ret)
+			pr_err("switching failed stage 1 %d\n", ret);
+
+		ret = vga_switchto_stage2(client);
+		if (ret)
+			pr_err("switching failed stage 2 %d\n", ret);
+
+	} else {
+		pr_info("setting delayed switch to client %d\n", client->id);
+		vgasr_priv.delayed_switch_active = true;
+		vgasr_priv.delayed_client_id = client_id;
+
+		ret = vga_switchto_stage1(client);
+		if (ret)
+			pr_err("delayed switching stage 1 failed %d\n", ret);
+	}
+
+out:
+	mutex_unlock(&vgasr_mutex);
+	return cnt;
+}
+
+static const struct file_operations vga_switcheroo_debugfs_fops = {
+	.owner = THIS_MODULE,
+	.open = vga_switcheroo_debugfs_open,
+	.write = vga_switcheroo_debugfs_write,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
+static void vga_switcheroo_debugfs_fini(struct vgasr_priv *priv)
+{
+	debugfs_remove_recursive(priv->debugfs_root);
+	priv->debugfs_root = NULL;
+}
+
+static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv)
+{
+	/* already initialised */
+	if (priv->debugfs_root)
+		return;
+
+	priv->debugfs_root = debugfs_create_dir("vgaswitcheroo", NULL);
+
+	debugfs_create_file("switch", 0644, priv->debugfs_root, NULL,
+			    &vga_switcheroo_debugfs_fops);
+}
+
+/**
+ * vga_switcheroo_process_delayed_switch() - helper for delayed switching
+ *
+ * Process a delayed switch if one is pending. DRM drivers should call this
+ * from their ->lastclose callback.
+ *
+ * Return: 0 on success. -EINVAL if no delayed switch is pending, if the client
+ * has unregistered in the meantime or if there are other clients blocking the
+ * switch. If the actual switch fails, an error is reported and 0 is returned.
+ */
+int vga_switcheroo_process_delayed_switch(void)
+{
+	struct vga_switcheroo_client *client;
+	int ret;
+	int err = -EINVAL;
+
+	mutex_lock(&vgasr_mutex);
+	if (!vgasr_priv.delayed_switch_active)
+		goto err;
+
+	pr_info("processing delayed switch to %d\n",
+		vgasr_priv.delayed_client_id);
+
+	client = find_client_from_id(&vgasr_priv.clients,
+				     vgasr_priv.delayed_client_id);
+	if (!client || !check_can_switch())
+		goto err;
+
+	ret = vga_switchto_stage2(client);
+	if (ret)
+		pr_err("delayed switching failed stage 2 %d\n", ret);
+
+	vgasr_priv.delayed_switch_active = false;
+	err = 0;
+err:
+	mutex_unlock(&vgasr_mutex);
+	return err;
+}
+EXPORT_SYMBOL(vga_switcheroo_process_delayed_switch);
+
+/**
+ * DOC: Driver power control
+ *
+ * In this mode of use, the discrete GPU automatically powers up and down at
+ * the discretion of the driver's runtime pm. On muxed machines, the user may
+ * still influence the muxer state by way of the debugfs interface, however
+ * the ON and OFF commands become a no-op for the discrete GPU.
+ *
+ * This mode is the default on Nvidia HybridPower/Optimus and ATI PowerXpress.
+ * Specifying nouveau.runpm=0, radeon.runpm=0 or amdgpu.runpm=0 on the kernel
+ * command line disables it.
+ *
+ * After the GPU has been suspended, the handler needs to be called to cut
+ * power to the GPU. Likewise it needs to reinstate power before the GPU
+ * can resume. This is achieved by vga_switcheroo_init_domain_pm_ops(),
+ * which augments the GPU's suspend/resume functions by the requisite
+ * calls to the handler.
+ *
+ * When the audio device resumes, the GPU needs to be woken. This is achieved
+ * by a PCI quirk which calls device_link_add() to declare a dependency on the
+ * GPU. That way, the GPU is kept awake whenever and as long as the audio
+ * device is in use.
+ *
+ * On muxed machines, if the mux is initially switched to the discrete GPU,
+ * the user ends up with a black screen when the GPU powers down after boot.
+ * As a workaround, the mux is forced to the integrated GPU on runtime suspend,
+ * cf. https://bugs.freedesktop.org/show_bug.cgi?id=75917
+ */
+
+static void vga_switcheroo_power_switch(struct pci_dev *pdev,
+					enum vga_switcheroo_state state)
+{
+	struct vga_switcheroo_client *client;
+
+	if (!vgasr_priv.handler->power_state)
+		return;
+
+	client = find_client_from_pci(&vgasr_priv.clients, pdev);
+	if (!client)
+		return;
+
+	if (!client->driver_power_control)
+		return;
+
+	vgasr_priv.handler->power_state(client->id, state);
+}
+
+/* switcheroo power domain */
+static int vga_switcheroo_runtime_suspend(struct device *dev)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	int ret;
+
+	ret = dev->bus->pm->runtime_suspend(dev);
+	if (ret)
+		return ret;
+	mutex_lock(&vgasr_mutex);
+	if (vgasr_priv.handler->switchto) {
+		mutex_lock(&vgasr_priv.mux_hw_lock);
+		vgasr_priv.handler->switchto(VGA_SWITCHEROO_IGD);
+		mutex_unlock(&vgasr_priv.mux_hw_lock);
+	}
+	pci_bus_set_current_state(pdev->bus, PCI_D3cold);
+	vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_OFF);
+	mutex_unlock(&vgasr_mutex);
+	return 0;
+}
+
+static int vga_switcheroo_runtime_resume(struct device *dev)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	mutex_lock(&vgasr_mutex);
+	vga_switcheroo_power_switch(pdev, VGA_SWITCHEROO_ON);
+	mutex_unlock(&vgasr_mutex);
+	pci_resume_bus(pdev->bus);
+	return dev->bus->pm->runtime_resume(dev);
+}
+
+/**
+ * vga_switcheroo_init_domain_pm_ops() - helper for driver power control
+ * @dev: vga client device
+ * @domain: power domain
+ *
+ * Helper for GPUs whose power state is controlled by the driver's runtime pm.
+ * After the GPU has been suspended, the handler needs to be called to cut
+ * power to the GPU. Likewise it needs to reinstate power before the GPU
+ * can resume. To this end, this helper augments the suspend/resume functions
+ * by the requisite calls to the handler. It needs only be called on platforms
+ * where the power switch is separate to the device being powered down.
+ */
+int vga_switcheroo_init_domain_pm_ops(struct device *dev,
+				      struct dev_pm_domain *domain)
+{
+	/* copy over all the bus versions */
+	if (dev->bus && dev->bus->pm) {
+		domain->ops = *dev->bus->pm;
+		domain->ops.runtime_suspend = vga_switcheroo_runtime_suspend;
+		domain->ops.runtime_resume = vga_switcheroo_runtime_resume;
+
+		dev_pm_domain_set(dev, domain);
+		return 0;
+	}
+	dev_pm_domain_set(dev, NULL);
+	return -EINVAL;
+}
+EXPORT_SYMBOL(vga_switcheroo_init_domain_pm_ops);
+
+void vga_switcheroo_fini_domain_pm_ops(struct device *dev)
+{
+	dev_pm_domain_set(dev, NULL);
+}
+EXPORT_SYMBOL(vga_switcheroo_fini_domain_pm_ops);