No display at boot

No display at boot

[陳勇秀]

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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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Re: No display at boot

[Jani Nikula]

On Tue, 23 Sep 2014, 陳勇秀 <greatshow.chen@gmail.com> wrote:
> 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.

Please file a bug against DRM/Intel at [1], attach dmesg all the way
from boot to the problem with drm.debug=14 module parameter set.

BR,
Jani.


[1] https://bugs.freedesktop.org/enter_bug.cgi?product=DRI


-- 
Jani Nikula, Intel Open Source Technology Center
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