path: root/drivers/gpu/vga/vgaarb.c

/*
 * vgaarb.c: Implements the VGA arbitration. For details refer to
 * Documentation/gpu/vgaarbiter.rst
 *
 *
 * (C) Copyright 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
 * (C) Copyright 2007 Paulo R. Zanoni <przanoni@gmail.com>
 * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti@freedesktop.org>
 *
 * 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) "vgaarb: " fmt

#define vgaarb_dbg(dev, fmt, arg...)	dev_dbg(dev, "vgaarb: " fmt, ##arg)
#define vgaarb_info(dev, fmt, arg...)	dev_info(dev, "vgaarb: " fmt, ##arg)
#define vgaarb_err(dev, fmt, arg...)	dev_err(dev, "vgaarb: " 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/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 {
	struct list_head list;
	struct pci_dev *pdev;
	unsigned int decodes;	/* what does it decodes */
	unsigned int owns;	/* what does it owns */
	unsigned int locks;	/* what does it locks */
	unsigned int io_lock_cnt;	/* legacy IO lock count */
	unsigned int mem_lock_cnt;	/* legacy MEM lock count */
	unsigned int io_norm_cnt;	/* normal IO count */
	unsigned int mem_norm_cnt;	/* normal MEM count */
	bool bridge_has_one_vga;
	/* allow IRQ enable/disable hook */
	void *cookie;
	void (*irq_set_state)(void *cookie, bool enable);
	unsigned int (*set_vga_decode)(void *cookie, bool decode);
};

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)
{
	/* Ignore VGA_RSRC_IO and VGA_RSRC_MEM */
	iostate &= VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
	switch (iostate) {
	case VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM:
		return "io+mem";
	case VGA_RSRC_LEGACY_IO:
		return "io";
	case VGA_RSRC_LEGACY_MEM:
		return "mem";
	}
	return "none";
}

static int vga_str_to_iostate(char *buf, int str_size, int *io_state)
{
	/* we could in theory hand out locks on IO and mem
	 * separately to userspace but it can cause deadlocks */
	if (strncmp(buf, "none", 4) == 0) {
		*io_state = VGA_RSRC_NONE;
		return 1;
	}

	/* XXX We're not chekcing the str_size! */
	if (strncmp(buf, "io+mem", 6) == 0)
		goto both;
	else if (strncmp(buf, "io", 2) == 0)
		goto both;
	else if (strncmp(buf, "mem", 3) == 0)
		goto both;
	return 0;
both:
	*io_state = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
	return 1;
}

/* this is only used a cookie - it should not be dereferenced */
static struct pci_dev *vga_default;

static void vga_arb_device_card_gone(struct pci_dev *pdev);

/* Find somebody in our list */
static struct vga_device *vgadev_find(struct pci_dev *pdev)
{
	struct vga_device *vgadev;

	list_for_each_entry(vgadev, &vga_list, list)
		if (pdev == vgadev->pdev)
			return vgadev;
	return NULL;
}

/**
 * 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 archs
 * 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 theirs 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)
{
	return vga_default;
}
EXPORT_SYMBOL_GPL(vga_default_device);

void vga_set_default_device(struct pci_dev *pdev)
{
	if (vga_default == pdev)
		return;

	pci_dev_put(vga_default);
	vga_default = pci_dev_get(pdev);
}

static inline void vga_irq_set_state(struct vga_device *vgadev, bool state)
{
	if (vgadev->irq_set_state)
		vgadev->irq_set_state(vgadev->cookie, state);
}


/* If we don't ever use VGA arb 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)
{
	/* we should inform all GPUs in the system that
	 * VGA arb has occurred and to try and disable resources
	 * if they can */
	if (!vga_arbiter_used) {
		vga_arbiter_used = true;
		vga_arbiter_notify_clients();
	}
}

static struct vga_device *__vga_tryget(struct vga_device *vgadev,
				       unsigned int rsrc)
{
	struct device *dev = &vgadev->pdev->dev;
	unsigned int wants, legacy_wants, match;
	struct vga_device *conflict;
	unsigned int pci_bits;
	u32 flags = 0;

	/* Account for "normal" resources to lock. If we decode the legacy,
	 * counterpart, we need to request it as well
	 */
	if ((rsrc & VGA_RSRC_NORMAL_IO) &&
	    (vgadev->decodes & VGA_RSRC_LEGACY_IO))
		rsrc |= VGA_RSRC_LEGACY_IO;
	if ((rsrc & VGA_RSRC_NORMAL_MEM) &&
	    (vgadev->decodes & VGA_RSRC_LEGACY_MEM))
		rsrc |= VGA_RSRC_LEGACY_MEM;

	vgaarb_dbg(dev, "%s: %d\n", __func__, rsrc);
	vgaarb_dbg(dev, "%s: owns: %d\n", __func__, vgadev->owns);

	/* Check what resources we need to acquire */
	wants = rsrc & ~vgadev->owns;

	/* We already own everything, just mark locked & bye bye */
	if (wants == 0)
		goto lock_them;

	/* We don't need to request a legacy resource, we just enable
	 * appropriate decoding and go
	 */
	legacy_wants = wants & VGA_RSRC_LEGACY_MASK;
	if (legacy_wants == 0)
		goto enable_them;

	/* Ok, we don't, let's find out how we need to kick off */
	list_for_each_entry(conflict, &vga_list, list) {
		unsigned int lwants = legacy_wants;
		unsigned int change_bridge = 0;

		/* Don't conflict with myself */
		if (vgadev == conflict)
			continue;

		/* Check if the architecture allows a conflict between those
		 * 2 devices or if they are on separate domains
		 */
		if (!vga_conflicts(vgadev->pdev, conflict->pdev))
			continue;

		/* We have a possible conflict. before we go further, we must
		 * check if we sit on the same bus as the conflicting device.
		 * if we don't, then we must tie both IO and MEM resources
		 * together since there is only a single bit controlling
		 * VGA forwarding on P2P bridges
		 */
		if (vgadev->pdev->bus != conflict->pdev->bus) {
			change_bridge = 1;
			lwants = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
		}

		/* Check i