Re: [PATCH v4 10/38] drm/i915: Force MMIO flips when scheduler enabled

John Harrison
2016-01-12T11:19:31Z

On 11/01/2016 22:16, Chris Wilson wrote:
> On Mon, Jan 11, 2016 at 06:42:39PM +0000, John.C.Harrison@Intel.com wrote:
>> From: John Harrison <John.C.Harrison@Intel.com>
>>
>> MMIO flips are the preferred mechanism now but more importantly,
> Says who?

I asked this exact question at the linux architecture forum quite some
time ago - does the scheduler need to worry about managing non-batch
buffer work such as page flips. The answer from everyone present was no,
MMIO flips are the way to go so don't over complicate the scheduler
trying to support ring flips. Indeed, execlist mode already forces MMIO
flips anyway.

>> pipe
>> based flips cause issues for the scheduler. Specifically, submitting
>> work to the rings around the side of the scheduler could cause that
>> work to be lost if the scheduler generates a pre-emption event on that
>> ring.
> That just says that you haven't designed for the ability to schedule a
> flip into the scheduler, including handling the priority bump that might
> required to hit the deadline.
> -Chris
>

Initially I was doing that. I was told to drop that work.