Jiri Kosina c12aba5aa0 drm/i915: stop using GMBUS IRQs on Gen4 chips ... Commit 28c70f162 ("drm/i915: use the gmbus irq for waits") switched to using GMBUS irqs instead of GPIO bit-banging for chipset generations 4 and above. It turns out though that on many systems this leads to spurious interrupts being generated, long after the register write to disable the IRQs has been issued. Typically this results in the spurious interrupt source getting disabled: [ 9.636345] irq 16: nobody cared (try booting with the "irqpoll" option) [ 9.637915] Pid: 4157, comm: ifup Tainted: GF 3.9.0-rc2-00341-g0863702 #422 [ 9.639484] Call Trace: [ 9.640731] <IRQ> [<ffffffff8109b40d>] __report_bad_irq+0x1d/0xc7 [ 9.640731] [<ffffffff8109b7db>] note_interrupt+0x15b/0x1e8 [ 9.640731] [<ffffffff810999f7>] handle_irq_event_percpu+0x1bf/0x214 [ 9.640731] [<ffffffff81099a88>] handle_irq_event+0x3c/0x5c [ 9.640731] [<ffffffff8109c139>] handle_fasteoi_irq+0x7a/0xb0 [ 9.640731] [<ffffffff8100400e>] handle_irq+0x1a/0x24 [ 9.640731] [<ffffffff81003d17>] do_IRQ+0x48/0xaf [ 9.640731] [<ffffffff8142f1ea>] common_interrupt+0x6a/0x6a [ 9.640731] <EOI> [<ffffffff8142f952>] ? system_call_fastpath+0x16/0x1b [ 9.640731] handlers: [ 9.640731] [<ffffffffa000d771>] usb_hcd_irq [usbcore] [ 9.640731] [<ffffffffa0306189>] yenta_interrupt [yenta_socket] [ 9.640731] Disabling IRQ #16 The really curious thing is now that irq 16 is _not_ the interrupt for the i915 driver when using MSI, but it _is_ the interrupt when not using MSI. So by all indications it seems like gmbus is able to generate a legacy (shared) interrupt in MSI mode on some configurations. I've tried to reproduce this and the differentiating thing seems to be that on unaffected systems no other device uses irq 16 (which seems to be the non-MSI intel gfx interrupt on all gm45). I have no idea how that even can happen. To avoid tempting this elephant into a rage, just disable gmbus interrupt support on gen 4. v2: Improve the commit message with exact details of what's going on. Also add a comment in the code to warn against this particular elephant in the room. v3: Move the comment explaing how gen4 blows up next to the definition of HAS_GMBUS_IRQ to keep the code-flow straight. Suggested by Chris Wilson. Signed-off-by: Jiri Kosina <jkosina@suse.cz> (v1) Acked-by: Chris Wilson <chris@chris-wilson.co.uk> References: https://lkml.org/lkml/2013/3/8/325 Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>		2013-03-20 00:03:16 +01:00
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drm	drm/i915: stop using GMBUS IRQs on Gen4 chips	2013-03-20 00:03:16 +01:00
vga	fbcon: fix locking harder	2013-02-08 12:02:43 +10:00
Makefile	gpu: remove gma500 stub driver	2013-02-20 17:54:58 +10:00