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

John Harrison John.C.Harrison at Intel.com
Tue Jan 12 03:19:26 PST 2016

On 11/01/2016 22:16, Chris Wilson wrote:
> On Mon, Jan 11, 2016 at 06:42:39PM +0000, John.C.Harrison at Intel.com wrote:
>> From: John Harrison <John.C.Harrison at 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.

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