Re: [Regression: 2.6.25-rc5: Blank Screen: Intel 945]

Re: [Regression: 2.6.25-rc5: Blank Screen: Intel 945]

[Jesse Barnes]

On Monday, March 24, 2008 8:07 pm Justin Madru wrote:
> Jesse Barnes wrote:
> > Good luck with the upgrade...
>
> Well, the upgrade went ok, and compiling the reg_dumper using the
> libpciaccess .deb from Bryce worked. Then I tried to add to the boot
> scripts a call to reg_dumper...
> ...To make a long story short...
> I somehow killed my boot scripts! Anyways, I did a fresh reinstall of
> Ubuntu 8.4 Beta.
>
> I'm still getting the blank screen problem with the 2.6.25-rc6 kernel,
> so I guess it wasn't a Ubuntu software problem (or I hope not, because that
> could be really hard to find).
>
> What I did was created a script that took a reg_dump every 6 secs for 1
> min. I made that as rc2.d/S01regdump so it should've been the very first
> thing called. So, I hope there's enough "data points" to see what's
> happening.
>
> Reg Dump Information
> 	http://jdserver.homelinux.org/linux/reg_dump.tar.bz2

Wow, that's a lot of dump files. :)

I was worried that in the "blank" case we may see the same register dump
as in the working case, but thankfully they're different.  In fact, in all
the dumps after 0 in the 2.6.25-blank case, both pipes are disabled and
the LCD itself is disabled.

The important bits:

@@ -24,7 +24,7 @@
 (II):          DVOB_SRCDIM: 0x00000000
 (II):          DVOC_SRCDIM: 0x00000000
 (II):           PP_CONTROL: 0x00000001 (power target: on)
-(II):            PP_STATUS: 0xc0000008 (on, ready, sequencing idle)
+(II):            PP_STATUS: 0x0000000a (off, not ready, sequencing idle)
 (II):         PFIT_CONTROL: 0x80002668
 (II):      PFIT_PGM_RATIOS: 0x00000000
 (II):      PORT_HOTPLUG_EN: 0x00000020
@@ -36,7 +36,7 @@
 (II):             DSPABASE: 0x00000000
 (II):             DSPASURF: 0x00000000
 (II):          DSPATILEOFF: 0x00000000
-(II):            PIPEACONF: 0x00000000 (disabled, single-wide)
+(II):            PIPEACONF: 0x000c0000 (disabled, single-wide)
 (II):             PIPEASRC: 0x027f01df (640, 480)
 (II):            PIPEASTAT: 0x80000203 (status: FIFO_UNDERRUN VSYNC_INT_STATUS VBLANK_INT_STATUS OREG_UPDATE_STATUS)
 (II):         FBC_CFB_BASE: 0x00000000
@@ -59,16 +59,16 @@
 (II):              VSYNC_A: 0x01eb01e9 (490 start, 492 end)
 (II):            BCLRPAT_A: 0x00000000
 (II):         VSYNCSHIFT_A: 0x00000000
-(II):             DSPBCNTR: 0x95000000 (enabled, pipe B)
+(II):             DSPBCNTR: 0x15000000 (disabled, pipe B)
 (II):           DSPBSTRIDE: 0x00000500 (1280 bytes)
 (II):              DSPBPOS: 0x00000000 (0, 0)
 (II):             DSPBSIZE: 0x01df027f (640, 480)
 (II):             DSPBBASE: 0x00000000
 (II):             DSPBSURF: 0x00000000
 (II):          DSPBTILEOFF: 0x00000000
-(II):            PIPEBCONF: 0x80000000 (enabled, single-wide)
+(II):            PIPEBCONF: 0x000c0000 (disabled, single-wide)
 (II):             PIPEBSRC: 0x027f01df (640, 480)
-(II):            PIPEBSTAT: 0x00000202 (status: VSYNC_INT_STATUS VBLANK_INT_STATUS)
+(II):            PIPEBSTAT: 0x00000242 (status: VSYNC_INT_STATUS LBLC_EVENT_STATUS VBLANK_INT_STATUS)
 (II):                 FPB0: 0x00031107 (n = 3, m1 = 17, m2 = 7)
 (II):                 FPB1: 0x00031108 (n = 3, m1 = 17, m2 = 8)
 (II):               DPLL_B: 0x98026003 (enabled, non-dvo, spread spectrum clock, LVDS mode, p1 = 2, p2 = 14, SDVO mult 1)

So somehow both pipes are getting disabled, and your LCD is getting turned
off and things never get re-enabled.  The X driver should have turned things
back on though, after detecting what's available.  Do you have your X logs
from the working & broken cases?  Also, did you try reproducing the blank
screen problem w/o gdm enabled as Bryce suggested?  That could help narrow
down if it's just an intelfb problem vs. a new intelfb/X driver interaction
bug.

I still don't know why this behavior would have changed between 2.6.24 and
2.6.25-rc though... maybe the fb guys have some clue about other fb changes
that may have affected things.

Thanks a lot for your hard work so far in debugging this...

Thanks,
Jesse

-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2008.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/

Re: [Regression: 2.6.25-rc5: Blank Screen: Intel 945]

[Jesse Barnes]

On Monday, March 31, 2008 12:24 pm Justin Madru wrote:
> Well, I disabled gdm and tryed to trigger the blank screen. I did about ~16
> reboots and it blanked out on me only 2 times. I was using a script to
> reboot and/or startx. One time I'm not exactly sure if X was started, so it
> might have blanked out on a "startx". The other time I'm fairly sure X
> wasn't started, so it blanked out on a terminal login.

Ok, so that might indicate something in the fb layer is killing it...

> Both of the blank outs were different than the ones with gdm started.
> Pressing ctrl+alt+f# changed nothing on the screen; the screen seemed
> almost completely off (no or little backlight). A few seconds after
> pressing the power button the shutdown splash screen would show, but this
> time it was _very_ faint.
>
> Usually, when gdm is enabled, pressing ctrl+alt+f# would "refresh" (or
> mode/resolution change) the screen, but it would still be blank. Also the
> backlight still seamed to be on and at full brightness (although, still
> displaying black).
>
> Well, I don't know what to say, it's the strangest of problems.

Yeah, seems pretty weird.  Given that you see it w/o the fb stuff loaded as 
well and we still have a few open bugs against the intel X driver regarding 
VT switch & mode programming, I don't think this is a real kernel regression.  
It's more likely that some timing or memory layout changed subtly and is 
causing to to hit one of our existing bugs more frequently that you did 
before.  Can you file a bug against the intel X driver at 
bugs.freedesktop.org so we can track it there?  Unless we can find a way to 
reproduce it reliably it'll probably take a long time to fix, but we don't 
want to lose it either...

Thanks,
Jesse

-------------------------------------------------------------------------
Check out the new SourceForge.net Marketplace.
It's the best place to buy or sell services for
just about anything Open Source.
http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace