[Intel-gfx] [RFC 10/14] drm/i915/pxp: Enable PXP power management

[Daniele Ceraolo Spurio]

On 2/6/2021 5:08 AM, Chris Wilson wrote:
> Quoting Chris Wilson (2021-02-06 13:06:05)
>> Quoting Daniele Ceraolo Spurio (2021-02-06 02:09:21)
>>> +       if (!ret) {
>>> +               ret = wait_for(!pxp->termination_in_progress, 10);
>> This only works by chance. The compiler doesn't even have to reload the
>> variable. See struct completion.

This was a last minute addition when I was told that waiting on the 
in_play state change was not enough to guarantee full invalidation and I 
admit I didn't fully think it through because I want to get the RFC out.

> It appears we already have a ready made one with the termination
> i915_request. But that will require RCU pointer management...
> -Chris

I've tried to keep this decoupled from the request because after the 
request completion there is an MMIO write and only after that we start 
waiting for the interrupt. I'll go with a struct completion.

Daniele