[Libva] [PATCH 2/2] batch: fix MI_FLUSH_DW for Broadwell.

[Gwenole Beauchesne]

Hi,

2014-05-14 10:10 GMT+02:00 Zhao, Yakui <yakui.zhao at intel.com>:
> On Wed, 2014-05-14 at 01:47 -0600, Gwenole Beauchesne wrote:
>> The MI_FLUSH_DW command contains 5 dwords on Broadwell, i.e. one extra
>> dword for the high order bits of the Address field.
>
> Thanks for your patch.
>
> What is wrong if this is applied?
> The 4 dwords are still ok to Broadwell.  And the address/data field are
> not used in the command of MI_FLUSH_DW.
> So the current command is correct for Broadwell.

Yes, it's still correct... until we use post-sync ops. But anyway, if
you want to keep at the minimum similar semantics to what used to be
used, then it's preferred to have the required provisions for handling
that. Before, we used the defaults (QWORD immediate, if any). Now, the
default semantics changed.

(Un)fortunately, a command stream verifier won't notice that, but if
you want to strictly implement the specs for consistency, an Address
is always 64-bits on Broadwell. If you don't want to follow the specs,
that's your call, just remember that in the future and update the code
accordingly.

Regards,
Gwenole.

>> ---
>>  src/intel_batchbuffer.c | 7 +++++--
>>  1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/intel_batchbuffer.c b/src/intel_batchbuffer.c
>> index bc564d5..01e04d5 100644
>> --- a/src/intel_batchbuffer.c
>> +++ b/src/intel_batchbuffer.c
>> @@ -247,13 +247,16 @@ intel_batchbuffer_emit_mi_flush(struct intel_batchbuffer *batch)
>>              }
>>
>>          } else {
>> +            const uint32_t extra_dword = !!IS_GEN8(intel->device_id);
>>              uint32_t cmd = MI_FLUSH_DW;
>>              if (batch->flag == I915_EXEC_BSD)
>>                  cmd |= MI_FLUSH_DW_VIDEO_PIPELINE_CACHE_INVALIDATE;
>>
>> -            __BEGIN_BATCH(batch, 4, batch->flag);
>> -            __OUT_BATCH(batch, cmd);
>> +            __BEGIN_BATCH(batch, 4|extra_dword, batch->flag);
>> +            __OUT_BATCH(batch, cmd|extra_dword);
>>              __OUT_BATCH(batch, 0);
>> +            if (extra_dword)
>> +                __OUT_BATCH(batch, 0);
>>              __OUT_BATCH(batch, 0);
>>              __OUT_BATCH(batch, 0);
>>              __ADVANCE_BATCH(batch);
>
>