3 files changed, 118 insertions, 27 deletions

diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index be8d4cb5861c..8a1021f2e319 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -61,7 +61,7 @@ struct vga_device {
         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);
@@ -165,6 +165,8 @@ static struct vga_device *__vga_tryget(struct vga_device *vgadev,
         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
          */
@@ -237,16 +239,23 @@ static struct vga_device *__vga_tryget(struct vga_device *vgadev,
                 /* looks like he doesn't have a lock, we can steal
                  * them from him
                  */
-                vga_irq_set_state(conflict, false);
 
+                flags = 0;
                 pci_bits = 0;
-                if (lwants & (VGA_RSRC_LEGACY_MEM|VGA_RSRC_NORMAL_MEM))
-                        pci_bits |= PCI_COMMAND_MEMORY;
-                if (lwants & (VGA_RSRC_LEGACY_IO|VGA_RSRC_NORMAL_IO))
-                        pci_bits |= PCI_COMMAND_IO;
 
-                pci_set_vga_state(conflict->pdev, false, pci_bits,
-                                  change_bridge);
+                if (!conflict->bridge_has_one_vga) {
+                        vga_irq_set_state(conflict, false);
+                        flags |= PCI_VGA_STATE_CHANGE_DECODES;
+                        if (lwants & (VGA_RSRC_LEGACY_MEM|VGA_RSRC_NORMAL_MEM))
+                                pci_bits |= PCI_COMMAND_MEMORY;
+                        if (lwants & (VGA_RSRC_LEGACY_IO|VGA_RSRC_NORMAL_IO))
+                                pci_bits |= PCI_COMMAND_IO;
+                }
+
+                if (change_bridge)
+                        flags |= PCI_VGA_STATE_CHANGE_BRIDGE;
+
+                pci_set_vga_state(conflict->pdev, false, pci_bits, flags);
                 conflict->owns &= ~lwants;
                 /* If he also owned non-legacy, that is no longer the case */
                 if (lwants & VGA_RSRC_LEGACY_MEM)
@@ -261,14 +270,24 @@ enable_them:
          * also have in "decodes". We can lock resources we don't decode but
          * not own them.
          */
+        flags = 0;
         pci_bits = 0;
-        if (wants & (VGA_RSRC_LEGACY_MEM|VGA_RSRC_NORMAL_MEM))
-                pci_bits |= PCI_COMMAND_MEMORY;
-        if (wants & (VGA_RSRC_LEGACY_IO|VGA_RSRC_NORMAL_IO))
-                pci_bits |= PCI_COMMAND_IO;
-        pci_set_vga_state(vgadev->pdev, true, pci_bits, !!(wants & VGA_RSRC_LEGACY_MASK));
 
-        vga_irq_set_state(vgadev, true);
+        if (!vgadev->bridge_has_one_vga) {
+                flags |= PCI_VGA_STATE_CHANGE_DECODES;
+                if (wants & (VGA_RSRC_LEGACY_MEM|VGA_RSRC_NORMAL_MEM))
+                        pci_bits |= PCI_COMMAND_MEMORY;
+                if (wants & (VGA_RSRC_LEGACY_IO|VGA_RSRC_NORMAL_IO))
+                        pci_bits |= PCI_COMMAND_IO;
+        }
+        if (!!(wants & VGA_RSRC_LEGACY_MASK))
+                flags |= PCI_VGA_STATE_CHANGE_BRIDGE;
+
+        pci_set_vga_state(vgadev->pdev, true, pci_bits, flags);
+
+        if (!vgadev->bridge_has_one_vga) {
+                vga_irq_set_state(vgadev, true);
+        }
         vgadev->owns |= (wants & vgadev->decodes);
 lock_them:
         vgadev->locks |= (rsrc & VGA_RSRC_LEGACY_MASK);
@@ -421,6 +440,62 @@ bail:
 }
 EXPORT_SYMBOL(vga_put);
 
+/* 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)
+{
+        struct vga_device *same_bridge_vgadev;
+        struct pci_bus *new_bus, *bus;
+        struct pci_dev *new_bridge, *bridge;
+
+        vgadev->bridge_has_one_vga = true;
+
+        if (list_empty(&vga_list))
+                return;
+
+        /* okay iterate the new devices bridge hierarachy */
+        new_bus = vgadev->pdev->bus;
+        while (new_bus) {
+                new_bridge = new_bus->self;
+
+                if (new_bridge) {
+                        /* go through list of devices already registered */
+                        list_for_each_entry(same_bridge_vgadev, &vga_list, list) {
+                                bus = same_bridge_vgadev->pdev->bus;
+                                bridge = bus->self;
+
+                                /* see if the share a bridge with this device */
+                                if (new_bridge == bridge) {
+                                        /* if their direct parent bridge is the same
+                                           as any bridge of this device then it can't be used
+                                           for that device */
+                                        same_bridge_vgadev->bridge_has_one_vga = false;
+                                }
+
+                                /* now iterate the previous devices bridge hierarchy */
+                                /* if the new devices parent bridge is in the other devices
+                                   hierarchy then we can't use it to control this device */
+                                while (bus) {
+                                        bridge = bus->self;
+                                        if (bridge) {
+                                                if (bridge == vgadev->pdev->bus->self)
+                                                        vgadev->bridge_has_one_vga = false;
+                                        }
+                                        bus = bus->parent;
+                                }
+                        }
+                }
+                new_bus = new_bus->parent;
+        }
+}
+
 /*
  * Currently, we assume that the "initial" setup of the system is
  * not sane, that is we come up with conflicting devices and let
@@ -500,6 +575,8 @@ static bool vga_arbiter_add_pci_device(struct pci_dev *pdev)
                 vga_default = pci_dev_get(pdev);
 #endif
 
+        vga_arbiter_check_bridge_sharing(vgadev);
+
         /* Add to the list */
         list_add(&vgadev->list, &vga_list);
         vga_count++;
@@ -1222,6 +1299,7 @@ static int __init vga_arb_device_init(void)
 {
         int rc;
         struct pci_dev *pdev;
+        struct vga_device *vgadev;
 
         rc = misc_register(&vga_arb_device);
         if (rc < 0)
@@ -1238,6 +1316,13 @@ static int __init vga_arb_device_init(void)
                 vga_arbiter_add_pci_device(pdev);
 
         pr_info("vgaarb: loaded\n");
+
+        list_for_each_entry(vgadev, &vga_list, list) {
+                if (vgadev->bridge_has_one_vga)
+                        pr_info("vgaarb: bridge control possible %s\n", pci_name(vgadev->pdev));
+                else
+                        pr_info("vgaarb: no bridge control possible %s\n", pci_name(vgadev->pdev));
+        }
         return rc;
 }
 subsys_initcall(vga_arb_device_init);
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 2472e7177b4b..a339237f4f96 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2875,31 +2875,34 @@ static int pci_set_vga_state_arch(struct pci_dev *dev, bool decode,
  * @dev: the PCI device
  * @decode: true = enable decoding, false = disable decoding
  * @command_bits: PCI_COMMAND_IO and/or PCI_COMMAND_MEMORY
- * @change_bridge: traverse ancestors and change bridges
+ * @change_bridge_flags: traverse ancestors and change bridges
+ * CHANGE_BRIDGE_ONLY / CHANGE_BRIDGE
  */
 int pci_set_vga_state(struct pci_dev *dev, bool decode,
-                      unsigned int command_bits, bool change_bridge)
+                      unsigned int command_bits, u32 flags)
 {
         struct pci_bus *bus;
         struct pci_dev *bridge;
         u16 cmd;
         int rc;
 
-        WARN_ON(command_bits & ~(PCI_COMMAND_IO|PCI_COMMAND_MEMORY));
+        WARN_ON((flags & PCI_VGA_STATE_CHANGE_DECODES) & (command_bits & ~(PCI_COMMAND_IO|PCI_COMMAND_MEMORY)));
 
         /* ARCH specific VGA enables */
-        rc = pci_set_vga_state_arch(dev, decode, command_bits, change_bridge);
+        rc = pci_set_vga_state_arch(dev, decode, command_bits, flags);
         if (rc)
                 return rc;
 
-        pci_read_config_word(dev, PCI_COMMAND, &cmd);
-        if (decode == true)
-                cmd |= command_bits;
-        else
-                cmd &= ~command_bits;
-        pci_write_config_word(dev, PCI_COMMAND, cmd);
+        if (flags & PCI_VGA_STATE_CHANGE_DECODES) {
+                pci_read_config_word(dev, PCI_COMMAND, &cmd);
+                if (decode == true)
+                        cmd |= command_bits;
+                else
+                        cmd &= ~command_bits;
+                pci_write_config_word(dev, PCI_COMMAND, cmd);
+        }
 
-        if (change_bridge == false)
+        if (!(flags & PCI_VGA_STATE_CHANGE_BRIDGE))
                 return 0;
 
         bus = dev->bus;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 96f70d7e058d..f2e57b2e6a81 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -915,8 +915,11 @@ int pci_cfg_space_size_ext(struct pci_dev *dev);
 int pci_cfg_space_size(struct pci_dev *dev);
 unsigned char pci_bus_max_busnr(struct pci_bus *bus);
 
+#define PCI_VGA_STATE_CHANGE_BRIDGE (1 << 0)
+#define PCI_VGA_STATE_CHANGE_DECODES (1 << 1)
+
 int pci_set_vga_state(struct pci_dev *pdev, bool decode,
-                      unsigned int command_bits, bool change_bridge);
+                      unsigned int command_bits, u32 flags);
 /* kmem_cache style wrapper around pci_alloc_consistent() */
 
 #include <linux/pci-dma.h>
@@ -1061,7 +1064,7 @@ static inline int pci_proc_domain(struct pci_bus *bus)
 
 /* some architectures require additional setup to direct VGA traffic */
 typedef int (*arch_set_vga_state_t)(struct pci_dev *pdev, bool decode,
-                      unsigned int command_bits, bool change_bridge);
+                      unsigned int command_bits, u32 flags);
 extern void pci_register_set_vga_state(arch_set_vga_state_t func);
 
 #else /* CONFIG_PCI is not enabled */