Hi
2012/12/4 Mika Kuoppala <mika.kuoppala at linux.intel.com>:
> If wrap just happened we need to prevent emitting waits for
> pre wrap values. Detect this and emit no-ops instead.
>
> v2: Use olr > seqno to detect wrap instead of *seqno == 0
> as suggested by Chris Wilson.
This commit introduces a bug on Haswell. Now when I'm typing my
password on GDM the screen keeps doing wrong rendering. It "blinks
blue". After logging in I don't see more problems.
>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
> ---
> drivers/gpu/drm/i915/intel_ringbuffer.c | 21 ++++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 36e1e13a..2305af5 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -626,11 +626,22 @@ gen6_ring_sync(struct intel_ring_buffer *waiter,
> if (ret)
> return ret;
>
> - intel_ring_emit(waiter,
> - dw1 | signaller->semaphore_register[waiter->id]);
> - intel_ring_emit(waiter, seqno);
> - intel_ring_emit(waiter, 0);
> - intel_ring_emit(waiter, MI_NOOP);
> + BUG_ON(!waiter->outstanding_lazy_request);
> +
> + /* If seqno wrap happened, omit the wait with no-ops */
> + if (likely(waiter->outstanding_lazy_request > seqno)) {
> + intel_ring_emit(waiter,
> + dw1 |
> + signaller->semaphore_register[waiter->id]);
> + intel_ring_emit(waiter, seqno);
> + intel_ring_emit(waiter, 0);
> + intel_ring_emit(waiter, MI_NOOP);
> + } else {
> + intel_ring_emit(waiter, MI_NOOP);
> + intel_ring_emit(waiter, MI_NOOP);
> + intel_ring_emit(waiter, MI_NOOP);
> + intel_ring_emit(waiter, MI_NOOP);
> + }
> intel_ring_advance(waiter);
>
> return 0;
> --
> 1.7.9.5
>
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--
Paulo Zanoni
