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Initial conversion to a PCI device using runtime PM
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bbswitch will now bind a driver to the PCI device, this should remove
races that can occur when a PCI device is removed after bbswitch is
loaded.

Fixes:
 - Fixed a crash on some laptops that trigger a hotplug (a problem
   since Linux 3.12,
   #100)
 - As a driver is bound, you cannot "accidentally" load nouveau/nvidia
   anymore and confuse the power state.

Removed pci_set_master, there is no need for access to the PCI BARs.
pci_enable_device is removed too as the memory regions are not needed.

TODO:
 - Remove unload_state, it is a no-op.
 - Update load_state doc (assume ON by default).
 - System suspend/resume probably needs special treatment to ensure that
   the device is off again.
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@Lekensteyn
Lekensteyn committed Jun 6, 2016
1 parent ca16c53 commit 5c7b3f5
Showing 1 changed file with 154 additions and 91 deletions.
245 changes: 154 additions & 91 deletions bbswitch.c
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Expand Up @@ -35,6 +35,7 @@
#include <linux/suspend.h>
#include <linux/seq_file.h>
#include <linux/pm_runtime.h>
#include <linux/pm_domain.h>
#include <linux/version.h>

#if LINUX_VERSION_CODE < KERNEL_VERSION(3,8,0)
Expand Down Expand Up @@ -93,9 +94,14 @@ static int dsm_type = DSM_TYPE_UNSUPPORTED;

/* The cached name of the discrete device (of the form "0000:01:00.0"). */
static char dis_dev_name[16];
/* dis_dev is non-NULL iff it is currently bound by bbswitch (and off). */
static struct pci_dev *dis_dev;
static acpi_handle dis_handle;

/* The PM domain that wraps the PCI device, used to ensure that power is
* available before the device is put in D0. ("Nvidia" DSM and PR3). */
static struct dev_pm_domain pm_domain;

static char *buffer_to_string(const char *buffer, size_t n, char *target) {
int i;
for (i=0; i<n; i++) {
Expand Down Expand Up @@ -233,82 +239,167 @@ static int bbswitch_acpi_on(void) {

// Returns 1 if the card is disabled, 0 if enabled
static int is_card_disabled(void) {
u32 cfg_word;
// read first config word which contains Vendor and Device ID. If all bits
// are enabled, the device is assumed to be off
pci_read_config_dword(dis_dev, 0, &cfg_word);
// if one of the bits is not enabled (the card is enabled), the inverted
// result will be non-zero and hence logical not will make it 0 ("false")
return !~cfg_word;
/* Assume that the device is disabled when our PCI driver found a device. */
return dis_dev != NULL;
}

static void bbswitch_off(void) {
if (is_card_disabled())
return;

// to prevent the system from possibly locking up, don't disable the device
// if it's still in use by a driver (i.e. nouveau or nvidia)
if (dis_dev->driver) {
pr_warn("device %s is in use by driver '%s', refusing OFF\n",
dev_name(&dis_dev->dev), dis_dev->driver->name);
return;
}
/* Power source handling. */

static int bbswitch_pmd_runtime_suspend(struct device *dev)
{
int ret;

pr_debug("Preparing for runtime suspend.\n");

/* Put the device in D3. */
ret = dev->bus->pm->runtime_suspend(dev);
if (ret)
return ret;

bbswitch_acpi_off();
/* TODO For PR3, disable them. */
return 0;
}

static int bbswitch_pmd_runtime_resume(struct device *dev)
{
pr_info("enabling discrete graphics\n");

bbswitch_acpi_on();
/* TODO For PR3, enable them. */

/* Now ensure that the device is actually put in D0 by PCI. */
return dev->bus->pm->runtime_resume(dev);
}

static void bbswitch_pmd_set(struct device *dev)
{
pm_domain.ops = *dev->bus->pm;
pm_domain.ops.runtime_resume = bbswitch_pmd_runtime_resume;
pm_domain.ops.runtime_suspend = bbswitch_pmd_runtime_suspend;
dev_pm_domain_set(dev, &pm_domain);
}


/* Nvidia device itself. */

static int bbswitch_pci_runtime_suspend(struct device *dev)
{
struct pci_dev *pdev = to_pci_dev(dev);

pr_info("disabling discrete graphics\n");

if (bbswitch_optimus_dsm()) {
pr_warn("Optimus ACPI call failed, the device is not disabled\n");
return;
}
bbswitch_optimus_dsm();

pci_save_state(dis_dev);
pci_clear_master(dis_dev);
pci_disable_device(dis_dev);
do {
struct acpi_device *ad = NULL;
int r;

r = acpi_bus_get_device(dis_handle, &ad);
if (r || !ad) {
pr_warn("Cannot get ACPI device for PCI device\n");
break;
}
if (ad->power.state == ACPI_STATE_UNKNOWN) {
pr_debug("ACPI power state is unknown, forcing D0\n");
ad->power.state = ACPI_STATE_D0;
}
} while (0);
pci_set_power_state(dis_dev, PCI_D3cold);
/* Save state now that the device is still awake, makes PCI layer happy */
pci_save_state(pdev);
/* TODO if _PR3 is supported, should this be PCI_D3hot? */
pci_set_power_state(pdev, PCI_D3hot);
return 0;
}

if (bbswitch_acpi_off())
pr_warn("The discrete card could not be disabled by a _DSM call\n");
static int bbswitch_pci_runtime_resume(struct device *dev)
{
pr_debug("Finishing runtime resume.\n");

return 0;
}

static void bbswitch_on(void) {
if (!is_card_disabled())
return;
static const struct dev_pm_ops bbswitch_pci_pm_ops = {
.runtime_suspend = bbswitch_pci_runtime_suspend,
.runtime_resume = bbswitch_pci_runtime_resume,
/* No runtime_idle callback, the default zero delay is sufficient. */
};

pr_info("enabling discrete graphics\n");
static int bbswitch_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
/* Only bind to the device which we discovered before. */
if (strcmp(dev_name(&pdev->dev), dis_dev_name))
return -ENODEV;

pr_debug("Found PCI device\n");
dis_dev = pdev;

bbswitch_pmd_set(&pdev->dev);

if (bbswitch_acpi_on())
pr_warn("The discrete card could not be enabled by a _DSM call\n");
/* Prevent kernel from detaching the PCI device for some devices that
* generate hotplug events. The graphics card is typically not physically
* removable. */
pci_ignore_hotplug(pdev);

pci_set_power_state(dis_dev, PCI_D0);
pci_restore_state(dis_dev);
if (pci_enable_device(dis_dev))
pr_warn("failed to enable %s\n", dev_name(&dis_dev->dev));
pci_set_master(dis_dev);
pm_runtime_set_active(&pdev->dev); /* clear any errors */
/* Use autosuspend to avoid lspci waking up the device multiple times. */
pm_runtime_set_autosuspend_delay(&pdev->dev, 2000);
pm_runtime_use_autosuspend(&pdev->dev);
pm_runtime_allow(&pdev->dev);
pm_runtime_put_autosuspend(&pdev->dev);
return 0;
}

static void bbswitch_pci_remove(struct pci_dev *pdev)
{
pr_debug("Removing PCI device\n");

pm_runtime_get_noresume(&pdev->dev);
pm_runtime_dont_use_autosuspend(&pdev->dev);
pm_runtime_forbid(&pdev->dev);

dev_pm_domain_set(&pdev->dev, NULL);

dis_dev = NULL;
}

/* power bus so we can read PCI configuration space */
static void dis_dev_get(void) {
if (dis_dev->bus && dis_dev->bus->self)
pm_runtime_get_sync(&dis_dev->bus->self->dev);
static const struct pci_device_id pciidlist[] = {
{ PCI_DEVICE(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID),
PCI_CLASS_DISPLAY_VGA << 8, 0xffff00 },
{ PCI_DEVICE(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID),
PCI_CLASS_DISPLAY_3D << 8, 0xffff00 },
{ 0, 0, 0 },
};

static struct pci_driver bbswitch_pci_driver = {
.name = KBUILD_MODNAME,
.id_table = pciidlist,
.probe = bbswitch_pci_probe,
.remove = bbswitch_pci_remove,
.driver.pm = &bbswitch_pci_pm_ops,
};


static void bbswitch_off(void) {
int ret;

/* Do nothing if the device was disabled before. */
if (dis_dev)
return;

ret = pci_register_driver(&bbswitch_pci_driver);
if (ret) {
pr_warn("Cannot register PCI device\n");
return;
}

/* If the probe failed, remove the driver such that it can be reprobed on
* the next registration. */
if (!dis_dev) {
#if 0
/* TODO discover the other driver name if possible. */
pr_warn("device %s is in use by driver '%s', refusing OFF\n",
dev_name(&dis_dev->dev), dis_dev->driver->name);
#endif

pr_warn("Could not bind to device, is it in use by an other driver?\n");
pci_unregister_driver(&bbswitch_pci_driver);
}
}

static void dis_dev_put(void) {
if (dis_dev->bus && dis_dev->bus->self)
pm_runtime_put_sync(&dis_dev->bus->self->dev);
static void bbswitch_on(void) {
/* Do nothing if no device exists that was previously disabled. */
if (!dis_dev)
return;

pci_unregister_driver(&bbswitch_pci_driver);
}

static ssize_t bbswitch_proc_write(struct file *fp, const char __user *buff,
Expand All @@ -321,25 +412,19 @@ static ssize_t bbswitch_proc_write(struct file *fp, const char __user *buff,
if (copy_from_user(cmd, buff, len))
return -EFAULT;

dis_dev_get();

if (strncmp(cmd, "OFF", 3) == 0)
bbswitch_off();

if (strncmp(cmd, "ON", 2) == 0)
bbswitch_on();

dis_dev_put();

return len;
}

static int bbswitch_proc_show(struct seq_file *seqfp, void *p) {
// show the card state. Example output: 0000:01:00:00 ON
dis_dev_get();
seq_printf(seqfp, "%s %s\n", dis_dev_name,
is_card_disabled() ? "OFF" : "ON");
dis_dev_put();
return 0;
}
static int bbswitch_proc_open(struct inode *inode, struct file *file) {
Expand Down Expand Up @@ -385,15 +470,14 @@ static int __init bbswitch_init(void) {
dev_name(&pdev->dev), (char *)buf.pointer);
} else {
strlcpy(dis_dev_name, dev_name(&pdev->dev), sizeof(dis_dev_name));
dis_dev = pdev;
dis_handle = handle;
pr_info("Found discrete VGA device %s: %s\n",
dev_name(&pdev->dev), (char *)buf.pointer);
}
kfree(buf.pointer);
}

if (dis_dev == NULL) {
if (dis_handle == NULL) {
pr_err("No discrete VGA device found\n");
return -ENODEV;
}
Expand Down Expand Up @@ -425,41 +509,20 @@ static int __init bbswitch_init(void) {
return -ENOMEM;
}

dis_dev_get();

if (!is_card_disabled()) {
/* We think the card is enabled, so ensure the kernel does as well */
if (pci_enable_device(dis_dev))
pr_warn("failed to enable %s\n", dev_name(&dis_dev->dev));
}

if (load_state == CARD_ON)
bbswitch_on();
else if (load_state == CARD_OFF)
if (load_state == CARD_OFF)
bbswitch_off();

pr_info("Succesfully loaded. Discrete card %s is %s\n",
dis_dev_name, is_card_disabled() ? "off" : "on");

dis_dev_put();

return 0;
}

static void __exit bbswitch_exit(void) {
remove_proc_entry("bbswitch", acpi_root_dir);

dis_dev_get();

if (unload_state == CARD_ON)
bbswitch_on();
else if (unload_state == CARD_OFF)
bbswitch_off();

pr_info("Unloaded. Discrete card %s is %s\n",
dev_name(&dis_dev->dev), is_card_disabled() ? "off" : "on");

dis_dev_put();
bbswitch_on();
pr_info("Unloaded\n");
}

module_init(bbswitch_init);
Expand Down

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