PinePhone: document a "reset" fix for blank screen during installation

[smithfred]

On a PinePhone (Beta edition) and Tow-Boot 2022.07-006, on booting from a microSD flashed with mmcboot.installer.img, the display remained blank, even though boot completed successfully (it had the same serial output as another PinePhone that did have display output, and tapping the screen region for the Tow-Boot installer shutdown button logged a shutdown message).

The same thing happened on multiple attempts even after removing/reinserting the battery, but using the PinePhone's reset button fixed the issue and resulted in display output on the next installer boot. Presumably there is some issue sometimes with the display/controller not being in the correct state on shutdown, and Tow-Boot doesn't handle this.

It would be useful to add a note about the above workaround to https://tow-boot.org/devices/pine64-pinephoneA64.html.

[quinn-dougherty]

Is this a pressing the down-volume button situation? I would've liked the docs to have put "Booting an operating system from an SD card will require holding the volume down button before and during the second vibration. When done successfully, the LED will turn aqua." earlier in the page instead of at the bottom, cuz it's such a mandatory thing!

[samueldr]

It sounds like a different issue; here @smithfred seems to always be able to boot the installer image (which does not require holding a volume key on allwinner systems)... Though the installer system seemingly doesn't setup the display our, or maybe the backlight is stuck off.

In any case, it's odd.