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@kernel-bugs.osdl.org Reporter: tasev.stefanoska@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@amd.com 2014-04-19 18:57:14 Auteur du commit: Christian König christian.koenig@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@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.