From 5c0f6ee766d7c689e71a7df5e5fa87941affd75a Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Thu, 15 Aug 2013 16:37:59 -0600 Subject: [PATCH] vgaarb: Fix VGA decodes changes MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When VGA decodes change we need to do a bit more evaluation of exactly what has changed. We don't necessarily give up all the old owns resources and we need to account for resources with locks. The new algorithm is: If something is added, update decodes. If legacy resources were added and none were there before, we have a new participant. If something is removed, update decodes. If we previously owned it, we no longer own it. If it was previously locked, invalidate all locks and release it. If legacy resources were removed and none are left, remove the participant from VGA arbitration. Previously we updated decodes, released ownership of everything that was previously decoded, ignored all locks, and went off looking for another device to transfer VGA to. In a test case where Intel IGD removes only legacy VGA memory decoding, this left the arbiter switching to discrete graphics without actually disabling legacy VGA IO from the IGD. As a bonus, we bumped up the count of VGA arbitration participants for no good reason. Signed-off-by: Alex Williamson Cc: Dave Airlie Acked-by: Dave Airlie Reviewed-by: Ville Syrjälä [danvet: Kill now unused variables, reported by the 0-day kernel builtbot.] Signed-off-by: Daniel Vetter --- drivers/gpu/vga/vgaarb.c | 41 +++++++++++++++++----------------------- 1 file changed, 17 insertions(+), 24 deletions(-) diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c index ea564711bb80..af0259708358 100644 --- a/drivers/gpu/vga/vgaarb.c +++ b/drivers/gpu/vga/vgaarb.c @@ -644,10 +644,12 @@ bail: static inline void vga_update_device_decodes(struct vga_device *vgadev, int new_decodes) { - int old_decodes; - struct vga_device *new_vgadev, *conflict; + int old_decodes, decodes_removed, decodes_unlocked; old_decodes = vgadev->decodes; + decodes_removed = ~new_decodes & old_decodes; + decodes_unlocked = vgadev->locks & decodes_removed; + vgadev->owns &= ~decodes_removed; vgadev->decodes = new_decodes; pr_info("vgaarb: device changed decodes: PCI:%s,olddecodes=%s,decodes=%s:owns=%s\n", @@ -656,31 +658,22 @@ static inline void vga_update_device_decodes(struct vga_device *vgadev, vga_iostate_to_str(vgadev->decodes), vga_iostate_to_str(vgadev->owns)); - - /* if we own the decodes we should move them along to - another card */ - if ((vgadev->owns & old_decodes) && (vga_count > 1)) { - /* set us to own nothing */ - vgadev->owns &= ~old_decodes; - list_for_each_entry(new_vgadev, &vga_list, list) { - if ((new_vgadev != vgadev) && - (new_vgadev->decodes & VGA_RSRC_LEGACY_MASK)) { - pr_info("vgaarb: transferring owner from PCI:%s to PCI:%s\n", pci_name(vgadev->pdev), pci_name(new_vgadev->pdev)); - conflict = __vga_tryget(new_vgadev, VGA_RSRC_LEGACY_MASK); - if (!conflict) - __vga_put(new_vgadev, VGA_RSRC_LEGACY_MASK); - break; - } - } + /* if we removed locked decodes, lock count goes to zero, and release */ + if (decodes_unlocked) { + if (decodes_unlocked & VGA_RSRC_LEGACY_IO) + vgadev->io_lock_cnt = 0; + if (decodes_unlocked & VGA_RSRC_LEGACY_MEM) + vgadev->mem_lock_cnt = 0; + __vga_put(vgadev, decodes_unlocked); } /* change decodes counter */ - if (old_decodes != new_decodes) { - if (new_decodes & (VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM)) - vga_decode_count++; - else - vga_decode_count--; - } + if (old_decodes & VGA_RSRC_LEGACY_MASK && + !(new_decodes & VGA_RSRC_LEGACY_MASK)) + vga_decode_count--; + if (!(old_decodes & VGA_RSRC_LEGACY_MASK) && + new_decodes & VGA_RSRC_LEGACY_MASK) + vga_decode_count++; pr_debug("vgaarb: decoding count now is: %d\n", vga_decode_count); } -- 2.20.1