Investigate PAGE_SCALE usage and over-allocation

[nchapman]

Problem

PAGE_SCALE is used to allocate ION memory buffers but appears to massively over-allocate:

480p mode (PAGE_SCALE=3):

• Allocates: 1920×1440 = 5.27 MB
• Actually uses: max ~800×720 = 1.1 MB
• Waste: ~4 MB (76%)

560p mode (PAGE_SCALE=2):

• Allocates: 1504×1120 = 3.21 MB
• Actually uses: max ~1000×864 = 1.7 MB
• Waste: ~1.5 MB (47%)

Current Behavior

#define PAGE_SCALE (is_560p ? 2 : 3)
#define PAGE_WIDTH (FIXED_WIDTH * PAGE_SCALE)
#define PAGE_HEIGHT (FIXED_HEIGHT * PAGE_SCALE)
#define PAGE_SIZE (PAGE_PITCH * PAGE_HEIGHT)

Buffer is allocated at PAGE_SIZE but surfaces are created at actual needed dimensions (vid.width × vid.height).

Questions

1. Why such large over-allocation? Original MinUI comment says "to support various scaling operations" but what specifically?
2. Is PAGE_WIDTH/HEIGHT ever used directly? Only trimuismart appears to create surfaces at PAGE dimensions
3. Can we reduce PAGE_SCALE? Would PAGE_SCALE=2 for 480p and PAGE_SCALE=1.5 for 560p work?
4. Is this legacy code? Maybe needed for older rendering paths that have since been removed?

Investigation Needed

• Check if reducing PAGE_SCALE breaks any scaling modes (native/aspect/fullscreen)
• Test with maximum scale factors (6x for GB 160×144)
• Verify no buffer overruns with tighter allocation
• Check original MinUI history for why these values were chosen

Impact

Not critical but could save 2-3 MB of ION memory per device, potentially improving stability on memory-constrained units.

References

• workspace/all/common/api.h:24-31 - PAGE definitions
• workspace/miyoomini/platform/platform.h:155 - PAGE_SCALE override
• workspace/miyoomini/platform/platform.c:303 - Buffer allocation