On Mon, Feb 23, 2015 at 11:58:14AM +0200, Imre Deak wrote: > Atm, it's possible that the interrupt handler is called when the device > is in D3 or some other low-power state. It can be due to another device > that is still in D0 state and shares the interrupt line with i915, or on > some platforms there could be spurious interrupts even without sharing > the interrupt line. The latter case was reported by Klaus Ethgen using a > Lenovo x61p machine (gen 4). He noticed this issue via a system > suspend/resume hang and bisected it to the following commit: > > commit e11aa362308f5de467ce355a2a2471321b15a35c > Author: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> > Date: Wed Jun 18 09:52:55 2014 -0700 > > drm/i915: use runtime irq suspend/resume in freeze/thaw > > This is a problem, since in low-power states IIR will always read > 0xffffffff resulting in an endless IRQ servicing loop. > > Fix this by handling interrupts only when the driver explicitly enables > them and so it's guaranteed that the interrupt registers return a valid > value. > > Note that this issue existed even before the above commit, since during > runtime suspend/resume we never unregistered the handler. > > v2: > - clarify the purpose of smp_mb() vs. synchronize_irq() in the > code comment(Chris) > > Reference: https://lkml.org/lkml/2015/2/11/205 > Reported-and-bisected-by: Klaus Ethgen <Klaus@xxxxxxxxx> > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> Thanks! That comment makes it very clear. Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
