Re: [PATCH] drm/i915: Allow null render state batchbuffers bigger than one page

[Oscar Mateo <oscar.mateo@intel.com>]

On 07/14/2017 08:08 AM, Chris Wilson wrote:
> Quoting Oscar Mateo (2017-07-14 15:52:59)
>>
>>
>> On 07/13/2017 03:28 PM, Rodrigo Vivi wrote:
>>> On Wed, May 3, 2017 at 9:31 AM, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>>>> On Wed, May 03, 2017 at 09:12:18AM +0000, Oscar Mateo wrote:
>>>>>      On 05/03/2017 08:52 AM, Mika Kuoppala wrote:
>>>>>
>>>>>    Oscar Mateo [1]<oscar.mateo@intel.com> writes:
>>>>>
>>>>>
>>>>>    On 05/02/2017 09:17 AM, Mika Kuoppala wrote:
>>>>>
>>>>>    Chris Wilson [2]<chris@chris-wilson.co.uk> writes:
>>>>>
>>>>>
>>>>>    On Fri, Apr 28, 2017 at 09:11:06AM +0000, Oscar Mateo wrote:
>>>>>
>>>>>    The new batchbuffer for CNL surpasses the 4096 byte mark.
>>>>>
>>>>>    Cc: Mika Kuoppala [3]<mika.kuoppala@intel.com>
>>>>>    Cc: Ben Widawsky [4]<ben@bwidawsk.net>
>>>>>    Signed-off-by: Oscar Mateo [5]<oscar.mateo@intel.com>
>>>>>
>>>>>    Evil, 4k+ of nothing-ness that userspace then has to configure for itself
>>>>>    for correctness anyway.
>>>>>
>>>>>    Patch looks ok, but still question the sanity.
>>>>>
>>>>>    Is there a requirement for CNL to init the renderstate?
>>>>>
>>>>>    I would like to drop the render state init from CNL if
>>>>>    we can't find evidence that it needs it. Bspec indicates
>>>>>    that it doesnt.
>>> I'd like to drop as well, and I was hearing people around telling we
>>> didn't need anymore,
>>> however without this during power on I had bad failures...
>>>
>> The best I could get from architecture (+Raf) is that setting valid and
>> coherent values for the whole render state is required as soon as the
>> context is created, no matter who does it. If you see failures when the
>> KMD does not do it, that means the UMD must be missing something, right?
> That is my initial response as well. The kernel does load one context,
> just so that the hardware always has space to write to on power saving.
> The only batch executed for it is the golden render state. Easy enough
> to only initialise that kernel context to isolate whether it is
> self-inflicted or that userspace overlooked something in its state
> management. (I have the view that even if userspace doesn't think it
> needs to use a particular bit of state today, tomorrow it will so will
> need it anyway!)
> -Chris

Rodrigo, you have access to a CNL: can you make this test? The idea is 
to find out if the root cause for the failures you were seeing is the 
kernel default context or in the UMD-created contexts.

Thanks,
Oscar

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