Re: 3.15.0-rc2 radeon HD 7480D [Aruba] blank display

[Alex Deucher]

On Mon, Apr 21, 2014 at 4:32 PM, Ken Moffat <zarniwhoop@xxxxxxxxxxxx> wrote:
>  I've just built 3.15.0-rc2 on this box, and discovered that I get a
> blank screen.  The boot appears to complete (it sends me information
> from SMART which is from my last bootscript), and it responds to
> MagicSysRQ to reboot.  I tried to login and run startx, but that
> didn't seem to make any difference - possibly something went wrong,
> it wasn't in my history when I booted a good kernel.
>
>  This machine uses a regular old VGA cable to connect it, the
> following lines in dmesg make me think it has chosen the wrong
> connector:

VGA is implemented as a DP to VGA bridge on APUs.

>
> Apr 21 19:32:45 bluesbreaker kernel: [    1.273246]
> [drm:radeon_dp_link_train_cr] *ERROR* displayport link status failed
> Apr 21 19:32:45 bluesbreaker kernel: [    1.273247]
> [drm:radeon_dp_link_train_cr] *ERROR* clock recovery failed
> Apr 21 19:32:45 bluesbreaker kernel: [    1.295116] Console:
> switching to colour frame buffer device 85x34
>
>  On a boot with 3.14.0 and earlier I get a different console size -
> Apr 21 20:42:44 bluesbreaker kernel: [    1.445992] Console:
> switching to colour frame buffer device 133x54
>
>  My console font is 12x22, and my screen is 1600x1200 but it looks
> as if 3.15-rc2 has fallen back to trying to use 1024x768.
>
>  I'm attaching what look like the relevant parts of the messages
> from the system logs for 3.15-rc2 and 3.14.0.
>
>  Any ideas, please ?  This is an AMD A4-5300 APU and not the world's
> fastest machine for bisecting :-(

I'd guess it's either the pll rework patches or the switch to the
common dp helper code patches.  It would be helpful if you could
bisect.

Alex
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