PROCESSOR-SDK-AM65X: Android HW composer DPI calculation

Matthew McKee

Hello,

I am curious about why Android's HW composer uses htotal and vtotal for calculating display DPI rather than hdisplay and vdisplay. In my understanding, the calculation is using the active area measurements (mmWidth and mmHeight) and a mm-to-in conversion which means the formula should be using the active area resolution. Is my understanding unsound or is there a bug in the following code?

http://git.ti.com/cgit/cgit.cgi/android/hardware-ti-am57x.git/commit/?h=d-pie-core-release&id=b9d1ef4713bab0ead7b0eacaa3d1e3f94469135d

Thanks,
Matt McKee

over 5 years ago

0 Mykhailo Sopiha over 5 years ago

Prodigy 10 points

Hi,

Sorry for late reply.

Actually this formula is the result of a series of experiments, which have been done before the DDK stride calculation bug was fixed (it was the real reason of icons corruption).

With this kind of calculations am57 boards had the most stable homescreen picture.

In general this data is not being used by android right now, unless error about ro.sf.lcd_dencity is ignored:

http://androidxref.com/9.0.0_r3/xref/frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp#856

This thing requires review and experimental verification with all available boards.

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PROCESSOR-SDK-AM65X: Android HW composer DPI calculation