[Intel-gfx] No display at boot

[陳勇秀]

Hi All,

I am using a baytrail cpu and linux kernel 3.14.7, and will echo some
message to /dev/tty1 during boot.

There is chance that no display output during boot, but I can use linux via
ttyS4, the HSUART.

Attached is output of intel_reg_dumper,
display.fail is register dump that no display output.
display_ok is register dump that display works.

There is difference between:

 DPLL_A_MD: 0x60ff2cdf  (ok)
 DPLL_A_MD: 0x70ff2ddf   (fail)

 DPLL_B: 0x60ff2cdf (disabled, dvo, VGA, TV A clock, unknown mode, p1 = 1,
p2 = 0)   (ok)
 DPLL_B: 0x70ff2ddf (disabled, dvo, TV A clock, unknown mode, p1 = 1, p2 =
0, using FPx1!)  (fail)

The bios dump is also attached. How do I read the bios dump file?

The problem can be reproduced even I update kernel to 3.14.18.


It's interesting the no display issue never happens if I boot into x-window
system.
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