Re: [PATCH v2 07/16] drm/i915: Add vblank based delayed watermark update mechanism

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Jun 04, 2014 at 11:01:01AM -0300, Paulo Zanoni wrote:
> > This function is only called at init/resume. It populates the software
> > state with something that matches the current hardware state. I guess
> > a comment explaning the purpose of the function is the best we can do
> > here, or do you have a better idea?
> 
> The problem is that we can use the get_hw_state functions not only to
> check driver state a init/resume, but also to do state tracking
> assertions at certain points of the code. Since most (all?) the other
> HW state readout functions don't have side-effects, there's a
> possibility that someone may add code to do HW state assertion at some
> points, and just call these things without realizing the potential
> side effects. A comment would help, but moving the assignment to
> another place would also solve the problem for me. You choose.

We already do that in other places, e.g. the edp bit depth hacks we have.
But a comment might be justified.

I haven't looked at the details here, just a high-level comment that we do
play such ugly tricks already. And I agree that it's unexpected.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch