// SPDX-License-Identifier: MIT /* * vgaarb.c: Implements VGA arbitration. For details refer to * Documentation/gpu/vgaarbiter.rst * * (C) Copyright 2005 Benjamin Herrenschmidt <[email protected]> * (C) Copyright 2007 Paulo R. Zanoni <[email protected]> * (C) Copyright 2007, 2009 Tiago Vignatti <[email protected]> */ #define pr_fmt(fmt) … #define vgaarb_dbg(dev, fmt, arg...) … #define vgaarb_info(dev, fmt, arg...) … #define vgaarb_err(dev, fmt, arg...) … #include <linux/module.h> #include <linux/kernel.h> #include <linux/pci.h> #include <linux/errno.h> #include <linux/init.h> #include <linux/list.h> #include <linux/sched/signal.h> #include <linux/wait.h> #include <linux/spinlock.h> #include <linux/poll.h> #include <linux/miscdevice.h> #include <linux/slab.h> #include <linux/screen_info.h> #include <linux/vt.h> #include <linux/console.h> #include <linux/acpi.h> #include <linux/uaccess.h> #include <linux/vgaarb.h> static void vga_arbiter_notify_clients(void); /* * We keep a list of all VGA devices in the system to speed * up the various operations of the arbiter */ struct vga_device { … }; static LIST_HEAD(vga_list); static int vga_count, vga_decode_count; static bool vga_arbiter_used; static DEFINE_SPINLOCK(vga_lock); static DECLARE_WAIT_QUEUE_HEAD(vga_wait_queue); static const char *vga_iostate_to_str(unsigned int iostate) { … } static int vga_str_to_iostate(char *buf, int str_size, unsigned int *io_state) { … } /* This is only used as a cookie, it should not be dereferenced */ static struct pci_dev *vga_default; /* Find somebody in our list */ static struct vga_device *vgadev_find(struct pci_dev *pdev) { … } /** * vga_default_device - return the default VGA device, for vgacon * * This can be defined by the platform. The default implementation is * rather dumb and will probably only work properly on single VGA card * setups and/or x86 platforms. * * If your VGA default device is not PCI, you'll have to return NULL here. * In this case, I assume it will not conflict with any PCI card. If this * is not true, I'll have to define two arch hooks for enabling/disabling * the VGA default device if that is possible. This may be a problem with * real _ISA_ VGA cards, in addition to a PCI one. I don't know at this * point how to deal with that card. Can their IOs be disabled at all? If * not, then I suppose it's a matter of having the proper arch hook telling * us about it, so we basically never allow anybody to succeed a vga_get(). */ struct pci_dev *vga_default_device(void) { … } EXPORT_SYMBOL_GPL(…); void vga_set_default_device(struct pci_dev *pdev) { … } /** * vga_remove_vgacon - deactivate VGA console * * Unbind and unregister vgacon in case pdev is the default VGA device. * Can be called by GPU drivers on initialization to make sure VGA register * access done by vgacon will not disturb the device. * * @pdev: PCI device. */ #if !defined(CONFIG_VGA_CONSOLE) int vga_remove_vgacon(struct pci_dev *pdev) { return 0; } #elif !defined(CONFIG_DUMMY_CONSOLE) int vga_remove_vgacon(struct pci_dev *pdev) { return -ENODEV; } #else int vga_remove_vgacon(struct pci_dev *pdev) { … } #endif EXPORT_SYMBOL(…); /* * If we don't ever use VGA arbitration, we should avoid turning off * anything anywhere due to old X servers getting confused about the boot * device not being VGA. */ static void vga_check_first_use(void) { … } static struct vga_device *__vga_tryget(struct vga_device *vgadev, unsigned int rsrc) { … } static void __vga_put(struct vga_device *vgadev, unsigned int rsrc) { … } /** * vga_get - acquire & lock VGA resources * @pdev: PCI device of the VGA card or NULL for the system default * @rsrc: bit mask of resources to acquire and lock * @interruptible: blocking should be interruptible by signals ? * * Acquire VGA resources for the given card and mark those resources * locked. If the resources requested are "normal" (and not legacy) * resources, the arbiter will first check whether the card is doing legacy * decoding for that type of resource. If yes, the lock is "converted" into * a legacy resource lock. * * The arbiter will first look for all VGA cards that might conflict and disable * their IOs and/or Memory access, including VGA forwarding on P2P bridges if * necessary, so that the requested resources can be used. Then, the card is * marked as locking these resources and the IO and/or Memory accesses are * enabled on the card (including VGA forwarding on parent P2P bridges if any). * * This function will block if some conflicting card is already locking one of * the required resources (or any resource on a different bus segment, since P2P * bridges don't differentiate VGA memory and IO afaik). You can indicate * whether this blocking should be interruptible by a signal (for userland * interface) or not. * * Must not be called at interrupt time or in atomic context. If the card * already owns the resources, the function succeeds. Nested calls are * supported (a per-resource counter is maintained) * * On success, release the VGA resource again with vga_put(). * * Returns: * * 0 on success, negative error code on failure. */ int vga_get(struct pci_dev *pdev, unsigned int rsrc, int interruptible) { … } EXPORT_SYMBOL(…); /** * vga_tryget - try to acquire & lock legacy VGA resources * @pdev: PCI device of VGA card or NULL for system default * @rsrc: bit mask of resources to acquire and lock * * Perform the same operation as vga_get(), but return an error (-EBUSY) * instead of blocking if the resources are already locked by another card. * Can be called in any context. * * On success, release the VGA resource again with vga_put(). * * Returns: * * 0 on success, negative error code on failure. */ static int vga_tryget(struct pci_dev *pdev, unsigned int rsrc) { … } /** * vga_put - release lock on legacy VGA resources * @pdev: PCI device of VGA card or NULL for system default * @rsrc: bit mask of resource to release * * Release resources previously locked by vga_get() or vga_tryget(). The * resources aren't disabled right away, so that a subsequent vga_get() on * the same card will succeed immediately. Resources have a counter, so * locks are only released if the counter reaches 0. */ void vga_put(struct pci_dev *pdev, unsigned int rsrc) { … } EXPORT_SYMBOL(…); static bool vga_is_firmware_default(struct pci_dev *pdev) { … } static bool vga_arb_integrated_gpu(struct device *dev) { … } /* * Return true if vgadev is a better default VGA device than the best one * we've seen so far. */ static bool vga_is_boot_device(struct vga_device *vgadev) { … } /* * Rules for using a bridge to control a VGA descendant decoding: if a bridge * has only one VGA descendant then it can be used to control the VGA routing * for that device. It should always use the bridge closest to the device to * control it. If a bridge has a direct VGA descendant, but also have a sub- * bridge VGA descendant then we cannot use that bridge to control the direct * VGA descendant. So for every device we register, we need to iterate all * its parent bridges so we can invalidate any devices using them properly. */ static void vga_arbiter_check_bridge_sharing(struct vga_device *vgadev) { … } /* * Currently, we assume that the "initial" setup of the system is not sane, * that is, we come up with conflicting devices and let the arbiter's * client decide if devices decodes legacy things or not. */ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev) { … } static bool vga_arbiter_del_pci_device(struct pci_dev *pdev) { … } /* Called with the lock */ static void vga_update_device_decodes(struct vga_device *vgadev, unsigned int new_decodes) { … } static void __vga_set_legacy_decoding(struct pci_dev *pdev, unsigned int decodes, bool userspace) { … } /** * vga_set_legacy_decoding * @pdev: PCI device of the VGA card * @decodes: bit mask of what legacy regions the card decodes * * Indicate to the arbiter if the card decodes legacy VGA IOs, legacy VGA * Memory, both, or none. All cards default to both, the card driver (fbdev for * example) should tell the arbiter if it has disabled legacy decoding, so the * card can be left out of the arbitration process (and can be safe to take * interrupts at any time. */ void vga_set_legacy_decoding(struct pci_dev *pdev, unsigned int decodes) { … } EXPORT_SYMBOL(…); /** * vga_client_register - register or unregister a VGA arbitration client * @pdev: PCI device of the VGA client * @set_decode: VGA decode change callback * * Clients have two callback mechanisms they can use. * * @set_decode callback: If a client can disable its GPU VGA resource, it * will get a callback from this to set the encode/decode state. * * Rationale: we cannot disable VGA decode resources unconditionally * because some single GPU laptops seem to require ACPI or BIOS access to * the VGA registers to control things like backlights etc. Hopefully newer * multi-GPU laptops do something saner, and desktops won't have any * special ACPI for this. The driver will get a callback when VGA * arbitration is first used by userspace since some older X servers have * issues. * * Does not check whether a client for @pdev has been registered already. * * To unregister, call vga_client_unregister(). * * Returns: 0 on success, -ENODEV on failure */ int vga_client_register(struct pci_dev *pdev, unsigned int (*set_decode)(struct pci_dev *pdev, bool decode)) { … } EXPORT_SYMBOL(…); /* * Char driver implementation * * Semantics is: * * open : Open user instance of the arbiter. By default, it's * attached to the default VGA device of the system. * * close : Close user instance, release locks * * read : Return a string indicating the status of the target. * An IO state string is of the form {io,mem,io+mem,none}, * mc and ic are respectively mem and io lock counts (for * debugging/diagnostic only). "decodes" indicate what the * card currently decodes, "owns" indicates what is currently * enabled on it, and "locks" indicates what is locked by this * card. If the card is unplugged, we get "invalid" then for * card_ID and an -ENODEV error is returned for any command * until a new card is targeted * * "<card_ID>,decodes=<io_state>,owns=<io_state>,locks=<io_state> (ic,mc)" * * write : write a command to the arbiter. List of commands is: * * target <card_ID> : switch target to card <card_ID> (see below) * lock <io_state> : acquire locks on target ("none" is invalid io_state) * trylock <io_state> : non-blocking acquire locks on target * unlock <io_state> : release locks on target * unlock all : release all locks on target held by this user * decodes <io_state> : set the legacy decoding attributes for the card * * poll : event if something change on any card (not just the target) * * card_ID is of the form "PCI:domain:bus:dev.fn". It can be set to "default" * to go back to the system default card (TODO: not implemented yet). * Currently, only PCI is supported as a prefix, but the userland API may * support other bus types in the future, even if the current kernel * implementation doesn't. * * Note about locks: * * The driver keeps track of which user has what locks on which card. It * supports stacking, like the kernel one. This complicates the implementation * a bit, but makes the arbiter more tolerant to userspace problems and able * to properly cleanup in all cases when a process dies. * Currently, a max of 16 cards simultaneously can have locks issued from * userspace for a given user (file descriptor instance) of the arbiter. * * If the device is hot-unplugged, there is a hook inside the module to notify * it being added/removed in the system and automatically added/removed in * the arbiter. */ #define MAX_USER_CARDS … #define PCI_INVALID_CARD … /* Each user has an array of these, tracking which cards have locks */ struct vga_arb_user_card { … }; struct vga_arb_private { … }; static LIST_HEAD(vga_user_list); static DEFINE_SPINLOCK(vga_user_lock); /* * Take a string in the format: "PCI:domain:bus:dev.fn" and return the * respective values. If the string is not in this format, return 0. */ static int vga_pci_str_to_vars(char *buf, int count, unsigned int *domain, unsigned int *bus, unsigned int *devfn) { … } static ssize_t vga_arb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { … } /* * TODO: To avoid parsing inside kernel and to improve the speed we may * consider use ioctl here */ static ssize_t vga_arb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { … } static __poll_t vga_arb_fpoll(struct file *file, poll_table *wait) { … } static int vga_arb_open(struct inode *inode, struct file *file) { … } static int vga_arb_release(struct inode *inode, struct file *file) { … } /* * Callback any registered clients to let them know we have a change in VGA * cards. */ static void vga_arbiter_notify_clients(void) { … } static int pci_notify(struct notifier_block *nb, unsigned long action, void *data) { … } static struct notifier_block pci_notifier = …; static const struct file_operations vga_arb_device_fops = …; static struct miscdevice vga_arb_device = …; static int __init vga_arb_device_init(void) { … } subsys_initcall_sync(vga_arb_device_init);
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