[Bug 42716] New: Boot failure with KMS enabled (radeon)

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=42716

           Summary: Boot failure with KMS enabled (radeon)
           Product: Drivers
           Version: 2.5
    Kernel Version: 3.2.x
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
        AssignedTo: drivers_video-dri at kernel-bugs.osdl.org
        ReportedBy: rw at rlworkman.net
        Regression: No


Since 3.2.0, my machine [1] fails to boot - it crashes/panics in early boot
when the radeon module (or one of its deps) is loaded. Graphics chip is as
follows:

  VGA compatible controller: ATI Technologies Inc RS690 [Radeon X1200 Series]

This is all running on libdrm-2.4.29, mesa-7.11.2, xorg-server-1.11.4, and
xf86-video-ati-6.14.3 with udev-180 (though the problem existed on 178 and 179
as well).

3.2.0, 3.2.1, and now 3.2.2 all exhibit this problem, but 3.1.x (including
3.1.10, which I'm currently using) is fine.  If I disable KMS
(radeon.modeset=0), then the system boots fine.

I thought I'd be clever and bisect this, so I built about twelve or thirteen
kernels, and bisect blamed this commit: 
  [50b8d257486a45cba7b65ca978986ed216bbcc10] ptrace: partially fix the
do_wait(WEXITED) vs EXIT_DEAD->EXIT_ZOMBIE race

That doesn't seem reasonable, but sure, it's worth a try.  I reversed that
patch in mainline 3.2.2, and I get a good boot.  However, I notice that this is
in /var/log/syslog:
  Feb  1 21:00:40 isotope kernel: [    2.039197] [drm:r100_ring_test] *ERROR*
radeon: ring test failed (scratch(0x15E4)=0xCAFEDEAD)
  Feb  1 21:00:40 isotope kernel: [    2.039256] [drm:r100_cp_init] *ERROR*
radeon: cp isn't working (-22).
  Feb  1 21:00:40 isotope kernel: [    2.162916] [drm:r100_cp_fini] *ERROR*
Wait for CP idle timeout, shutting down CP.

I then booted the vanilla 3.2.2, and it booted just fine.  Okay, that's odd, so
let's try the patched (reversed bisect patch from above) again.  This time,
appeared to OOPS after switching over to KMS, but the display is still visible.
 All of the potentially useful stuff scrolled off the screen, and now there's a
constant repetition of the following two lines (with alternating values of
CONNECTOR between 17 and 18) flooding the console every few seconds, so I can't
pageup back to the OOPS/trace/whatever:

  [drm:radeon_atombios_connected_scratch_regs], DFP3 disconnected
  [drm:output_poll_execute], [CONNECTOR:18:DVI-D-1] status updated from 2 to 2


So, let's reboot to that kernel a few times.
#1: all is fine
#2: crash/panic after kms load; no video at all
#3: crash/panic after kms load; no video at all

This isn't going well, so let's boot the patched kernel again:
#1: all is fine
#2: all is fine
#3: crash/panic after kms load; no video at all

Any idea what's going on here?  I don't have the option to attach a serial
console, for what that's worth, so that aside, any suggestions for further
debugging?

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