Chris Wilson <ch...@chris-wilson.co.uk> writes:

> On Tue, 18 Dec 2012 19:26:18 +0200, Mika Kuoppala 
> <mika.kuopp...@linux.intel.com> wrote:
>> Hardware status page needs to have proper seqno set
>> as our initial seqno can be arbitrary. If initial seqno is close
>> to wrap boundary on init and i915_seqno_passed() (31bit space)
>> refers to hw status page which contains zero, errorneous result
>> will be returned.
>> 
>> v2: clear mboxes and set hws page directly instead of going
>> through rings. Suggested by Chris Wilson.
>> 
>> v3: hws needs to be updated for all gens. Noticed by Chris
>> Wilson.
>> 
>> References: https://bugs.freedesktop.org/show_bug.cgi?id=58230
>> Signed-off-by: Mika Kuoppala <mika.kuopp...@intel.com>
>
>> -int intel_ring_handle_seqno_wrap(struct intel_ring_buffer *ring)
>> +void intel_ring_init_seqno(struct intel_ring_buffer *ring, u32 seqno)
>>  {
>> -    int ret;
>> +    struct drm_i915_private *dev_priv = ring->dev->dev_private;
>>  
>>      BUG_ON(ring->outstanding_lazy_request);
>>  
>> -    if (INTEL_INFO(ring->dev)->gen < 6)
>> -            return 0;
>> -
>> -    ret = __intel_ring_begin(ring, 6 * sizeof(uint32_t));
>> -    if (ret)
>> -            return ret;
>> -
>> -    /* Leaving a stale, pre-wrap seqno behind in the mboxes will result in
>> -     * post-wrap semaphore waits completing immediately. Clear them. */
>> -    update_mboxes(ring, ring->signal_mbox[0]);
>> -    update_mboxes(ring, ring->signal_mbox[1]);
>> -    intel_ring_advance(ring);
>> +    if (INTEL_INFO(ring->dev)->gen >= 6) {
>> +            I915_WRITE(RING_SYNC_0(ring->mmio_base), 0);
>> +            I915_WRITE(RING_SYNC_1(ring->mmio_base), 0);
>> +    }
>>  
>> -    return 0;
>> +    intel_write_status_page(ring, I915_GEM_HWS_INDEX, seqno);
>
> There's yet another complication here: not all gen use the HWS. Ironlake
> uses a pipecontrol write to another page -- though in principle we could
> write to the HWS instead.
>

I posted a new series which adds ring::set_seqno to take care per
architecture seqno writing...
 
> Any one feel like that challenge?

... and i will rip the ring:set_seqno out when ilk uses hws.

-Mika

> -Chris
>
> -- 
> Chris Wilson, Intel Open Source Technology Centre
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