[Intel-gfx] [PATCH 1/2] drm/i915: Improve irq handling after gpu resets
Ville Syrjälä
ville.syrjala at linux.intel.com
Mon May 26 10:36:33 CEST 2014
On Thu, May 22, 2014 at 10:18:21PM +0200, Daniel Vetter wrote:
> Currently we do a full re-init of all interrupts after a gpu hang.
> Which is pretty bad since we don't restore the interrupts we've
> enabled at runtime correctly. Even with that addressed it's rather
> horribly race.
>
> But on g4x and later we only reset the gt and not the entire gpu.
> Which means we only need to reset the GT interrupt bits. Which has the
> nice benefit that vblank waits, pipe CRC interrupts and everything
> else display related just keeps on working.
>
> The downside is that gt interrupt handling (i.e. ring->get/put_irq) is
> still racy. But as long as the gpu hang reliably wakes all waters and
> we have a short time where the refcount drops to 0 we'll recover. So
> not that bad really.
>
> v2: Ville noticed that GTIMR and PMIMR don't get cleared, only the
> subordinate per-ring registers. So let's rip out all the interrupt dancing.
> The FIXME comment is still required though since the ring irq handling
> happens at the per-ring interrupt mask registers, too.
>
> Testcase: igt/kms_flip/vblank-vs-hang
> Testcase: igt/kms_pipe_crc_basic/hang-*
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Both patches:
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
And to answer you earlier question, yes things seemd to work fine after
a GPU reset if I didn't touch the interrupt registers. In fact I also
tried killing most of the gem_hw_init() stuff (basically just left
ring->init(), l3_remap, and context enable) and things still seemed to
work just fine.
> ---
> drivers/gpu/drm/i915/i915_drv.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index c83c83b74bf4..7ae906c811bb 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -811,17 +811,17 @@ int i915_reset(struct drm_device *dev)
> }
>
> /*
> - * FIXME: This is horribly race against concurrent pageflip and
> - * vblank wait ioctls since they can observe dev->irqs_disabled
> - * being false when they shouldn't be able to.
> + * FIXME: This races pretty badly against concurrent holders of
> + * ring interrupts. This is possible since we've started to drop
> + * dev->struct_mutex in select places when waiting for the gpu.
> */
> - drm_irq_uninstall(dev);
> - drm_irq_install(dev, dev->pdev->irq);
>
> - /* rps/rc6 re-init is necessary to restore state lost after the
> - * reset and the re-install of drm irq. Skip for ironlake per
> + /*
> + * rps/rc6 re-init is necessary to restore state lost after the
> + * reset and the re-install of gt irqs. Skip for ironlake per
> * previous concerns that it doesn't respond well to some forms
> - * of re-init after reset. */
> + * of re-init after reset.
> + */
> if (INTEL_INFO(dev)->gen > 5)
> intel_reset_gt_powersave(dev);
I'm suspecting that GPU reset doesn't affect the RPS/RC6 stuff either.
But I suppose it shouldn't really hurt anything to do it, so it's just
something to look into if we want to reduce the amount of stuff we do
at reset.
--
Ville Syrjälä
Intel OTC
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