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drm_hwcomposer: Choose client layer range to achieve minimal GPU load

Merged Roman Stratiienko requested to merge roman.stratiienko/drm-hwcomposer:client-layer-position-pr into master
  1. Allow CLIENT layer at any position.
  2. Check all possible layer combination and choose most efficient based on total pixel operations value.

Use case 1 - Layer count is greater than available planes Table shows difference before and after this commit for 4 or 2 planes cases:

z_order   layer      size        pixels  before(4)  after(4) before(2) after(2)
-
0         Wallpaper  1960x1080   2MiP    CLIENT     DEVICE   CLIENT    DEVICE
1         Launcher   1960x1080   2MiP    CLIENT     DEVICE   CLIENT    CLIENT
2         Status bar 1960x80     0.15MiP DEVICE     DEVICE   CLIENT    CLIENT
3         Nav. bar   1960x80     0.15MiP DEVICE     CLIENT   CLIENT    CLIENT
4         Cursor     24x24       576P    DEVICE     CLIENT   DEVICE    CLIENT

Total pixels merged by CLIENT (GPU)      4MiP  ->   0.15MiP  4.3MiP -> 2.3MiP

Use case 2 - Unsupported layer type in the middle (Dim layer, etc): Table shows difference before and after this commit for 4 or 2 planes cases:

z_order   layer      size        pixels  before(4)  after(4) before(2) after(2)
-
0         App        1960x1080   2MiP    CLIENT     DEVICE   CLIENT    DEVICE
1         Status bar 1960x80     0.15MiP CLIENT     DEVICE   CLIENT    CLIENT
2         Nav. bar   1960x80     0.15MiP CLIENT     DEVICE   CLIENT    CLIENT
3         Dim layer  1960x1080   2MiP    CLIENT     CLIENT   CLIENT    CLIENT
4         Dialog     1000x500    0.5MiP  DEVICE     CLIENT   DEVICE    CLIENT

Total pixels merged by CLIENT (GPU)      4.3MiP ->  2.5MiP   4.3MiP -> 2.8MiP

This MR significantly speeds-up performance on slow GPUs with complex composition cases and high resolution displays.

Validated on sun4i DRM on H3 SOC, Orange PI plus2e board.

Edited by Roman Stratiienko