drm/i915: introduce intel_fbc_{enable,disable}
The goal is to call FBC enable/disable only once per modeset, while activate/deactivate/update will be called multiple times. The enable() function will be responsible for deciding if a CRTC will have FBC on it and then it will "lock" FBC on this CRTC: it won't be possible to change FBC's CRTC until disable(). With this, all checks and resource acquisition that only need to be done once per modeset can be moved from update() to enable(). And then the update(), activate() and deactivate() code will also get simpler since they won't need to worry about the CRTC being changed. The disable() function will do the reverse operation of enable(). One of its features is that it should only be called while the pipe is already off. This guarantees that FBC is stopped and nothing is using the CFB. With this, the activate() and deactivate() functions just start and temporarily stop FBC. They are the ones touching the hardware enable bit, so HW state reflects dev_priv->crtc.active. The last function remaining is update(). A lot of times I thought about renaming update() to activate() or try_to_activate() since it's called when we want to activate FBC. The thing is that update() may not only decide to activate FBC, but also deactivate or keep it on the same state, so I'll leave this name for now. Moving code to enable() and disable() will also help in case we decide to move FBC to pipe_config or something else later. The current patch only puts the very basic code on enable() and disable(). The next commits will take care of moving more stuff from update() to the new functions. v2: - Rebase. - Improve commit message (Chris). v3: Rebase after changing the patch order. v4: Rebase again after upstream changes. Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/
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