[Bug 75471] New: Black screen with frequency out of range with kernel 3.15-rc3 on radeon RS880

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=75471

            Bug ID: 75471
           Summary: Black screen with frequency out of range with kernel
                    3.15-rc3 on radeon RS880
           Product: Drivers
           Version: 2.5
    Kernel Version: 3.15-rc3
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri at kernel-bugs.osdl.org
          Reporter: tasev.stefanoska at skynet.be
        Regression: No

Created attachment 135071
  --> https://bugzilla.kernel.org/attachment.cgi?id=135071&action=edit
dmesg broken 3.15-rc3 kernel

I just have a black screen with frequency out of range on the monitor with the
kernel 3.15-rc3.The system boot normaly but after 3 seconds wen it should
display the splash screen comme the frequency out of range on the monitor, but
the boot process continue in the dark as normal and the system is responsive.
Everything work fine in 3.15-rc1 and rc2 kernels.

I'm running Kubuntu 12.04 Precise.
I have a RS880 motherboard with :

01:05.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RS880
[Radeon HD 4200].

After bisecting the first bad commit found :

first bad commit 24315814239a3fdb306244c99bd076bc79db4ade

Auteur: Christian König <christian.koenig at amd.com>  2014-04-19 18:57:14
Auteur du commit: Christian König <christian.koenig at amd.com>  2014-04-19
18:57:14
Parent: 76e6dcece841faebbee78895780e8209ff40d922 (drm/radeon: disable dpm on
rv770 by default)
Branche: master, remotes/origin/master
Suit: v3.15-rc1
Précède: v3.15-rc3

    drm/radeon: use fixed PPL ref divider if needed

    Signed-off-by: Christian König <christian.koenig at amd.com>

------------------- drivers/gpu/drm/radeon/radeon_display.c -------------------
index 2f7cbb9..e6c3c54 100644
@@ -880,7 +880,12 @@ void radeon_compute_pll_avivo(struct radeon_pll *pll,
         ref_div_min = pll->reference_div;
     else
         ref_div_min = pll->min_ref_div;
-    ref_div_max = pll->max_ref_div;
+
+    if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV &&
+        pll->flags & RADEON_PLL_USE_REF_DIV)
+        ref_div_max = pll->reference_div;
+    else
+        ref_div_max = pll->max_ref_div;

     /* determine allowed post divider range */
     if (pll->flags & RADEON_PLL_USE_POST_DIV) {


But sadly reverting the patch and rebuild the kernel doesn't fix the issue.

Attached are dmesg with drm_debug=0xe for the 3.15rc3 (broken) and 3.15-rc2 
kernels, and also the bisect.log.

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