Bug 93477

Summary: loop in pipe configuration computation
Product: DRI Reporter: Chris Wilson <chris>
Component: DRM/IntelAssignee: Maarten Lankhorst <bugs>
Status: CLOSED FIXED QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: medium CC: intel-gfx-bugs
Version: DRI git   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: HSW i915 features: display/atomic
Attachments:
Description Flags
dmesg
none
drm.debug=0x1f dmesg none

Description Chris Wilson 2015-12-22 20:17:43 UTC 
[  233.751747] ------------[ cut here ]------------
[  233.751759] WARNING: CPU: 2 PID: 3737 at drivers/gpu/drm/i915/intel_display.c:12407 intel_atomic_check+0xe9c/0x1100()
[  233.751761] loop in pipe configuration computation
[  233.751764] CPU: 2 PID: 3737 Comm: Xorg Tainted: G        W       4.4.0-rc6+ #501
[  233.751766] Hardware name: Intel Corporation Shark Bay Client platform/Basking Ridge, BIOS HSWLPTU1.86C.0131.R01.1307040815 07/04/2013
[  233.751767]  ffffffff8179a8b0 ffff8800a1adfaa8 ffffffff8125b4e9 0000000000000000
[  233.751772]  ffff8800a1adfaf8 ffff8800a1adfae8 ffffffff8106c342 000008c8000007f8
[  233.751776]  ffff8800a1a03600 0000000000000001 ffff880148b7d000 ffff880148b4e000
[  233.751779] Call Trace:
[  233.751786]  [<ffffffff8125b4e9>] dump_stack+0x45/0x5c
[  233.751789]  [<ffffffff8106c342>] warn_slowpath_common+0x92/0xd0
[  233.751791]  [<ffffffff8106c3f6>] warn_slowpath_fmt+0x46/0x50
[  233.751794]  [<ffffffff813bb264>] ? intel_link_compute_m_n+0x54/0x70
[  233.751795]  [<ffffffff813bc11c>] intel_atomic_check+0xe9c/0x1100
[  233.751799]  [<ffffffff8133c7af>] drm_atomic_check_only+0x15f/0x5b0
[  233.751801]  [<ffffffff8133c2c9>] ? drm_atomic_set_crtc_for_connector+0x29/0xa0
[  233.751803]  [<ffffffff8133cc20>] drm_atomic_commit+0x20/0x70
[  233.751808]  [<ffffffff813183a7>] drm_atomic_helper_set_config+0x77/0xb0
[  233.751811]  [<ffffffff8132b508>] drm_mode_set_config_internal+0x68/0x100
[  233.751813]  [<ffffffff8132b8a8>] drm_mode_setcrtc+0xe8/0x510
[  233.751815]  [<ffffffff813217f5>] drm_ioctl+0x255/0x4f0
[  233.751818]  [<ffffffff811b85e9>] ? ext4_file_write_iter+0x159/0x370
[  233.751820]  [<ffffffff8132b7c0>] ? drm_crtc_check_viewport+0xa0/0xa0
[  233.751823]  [<ffffffff8115b2e3>] do_vfs_ioctl+0x83/0x4d0
[  233.751826]  [<ffffffff81075e07>] ? recalc_sigpending+0x17/0x30
[  233.751827]  [<ffffffff81076437>] ? __set_task_blocked+0x37/0x80
[  233.751830]  [<ffffffff8114e042>] ? __sb_end_write+0x22/0x30
[  233.751832]  [<ffffffff8107887f>] ? __set_current_blocked+0x3f/0x60
[  233.751834]  [<ffffffff8115b77c>] SyS_ioctl+0x4c/0x90
[  233.751836]  [<ffffffff81078add>] ? SyS_rt_sigprocmask+0x8d/0xb0
[  233.751840]  [<ffffffff8152e6d7>] entry_SYSCALL_64_fastpath+0x12/0x6a
[  233.751841] ---[ end trace c24109ba1fac09a5 ]---
[  233.753439] ------------[ cut here ]------------
[  233.753445] WARNING: CPU: 2 PID: 3737 at drivers/gpu/drm/i915/intel_display.c:12407 intel_atomic_check+0xe9c/0x1100()
[  233.753447] loop in pipe configuration computation
[  233.753448] CPU: 2 PID: 3737 Comm: Xorg Tainted: G        W       4.4.0-rc6+ #501
[  233.753450] Hardware name: Intel Corporation Shark Bay Client platform/Basking Ridge, BIOS HSWLPTU1.86C.0131.R01.1307040815 07/04/2013
[  233.753451]  ffffffff8179a8b0 ffff8800a1adfaa8 ffffffff8125b4e9 0000000000000000
[  233.753454]  ffff8800a1adfaf8 ffff8800a1adfae8 ffffffff8106c342 000008c8000007f8
[  233.753457]  ffff8800a148f000 0000000000000001 ffff880148b7d000 ffff880148b4e000
[  233.753460] Call Trace:
[  233.753463]  [<ffffffff8125b4e9>] dump_stack+0x45/0x5c
[  233.753466]  [<ffffffff8106c342>] warn_slowpath_common+0x92/0xd0
[  233.753467]  [<ffffffff8106c3f6>] warn_slowpath_fmt+0x46/0x50
[  233.753469]  [<ffffffff813bb264>] ? intel_link_compute_m_n+0x54/0x70
[  233.753470]  [<ffffffff813bc11c>] intel_atomic_check+0xe9c/0x1100
[  233.753472]  [<ffffffff8133c7af>] drm_atomic_check_only+0x15f/0x5b0
[  233.753474]  [<ffffffff8133c2c9>] ? drm_atomic_set_crtc_for_connector+0x29/0xa0
[  233.753476]  [<ffffffff8133cc20>] drm_atomic_commit+0x20/0x70
[  233.753479]  [<ffffffff813183a7>] drm_atomic_helper_set_config+0x77/0xb0
[  233.753481]  [<ffffffff8132b508>] drm_mode_set_config_internal+0x68/0x100
[  233.753482]  [<ffffffff8132b8a8>] drm_mode_setcrtc+0xe8/0x510
[  233.753484]  [<ffffffff813217f5>] drm_ioctl+0x255/0x4f0
[  233.753486]  [<ffffffff8132b7c0>] ? drm_crtc_check_viewport+0xa0/0xa0
[  233.753488]  [<ffffffff8115b2e3>] do_vfs_ioctl+0x83/0x4d0
[  233.753490]  [<ffffffff81075e07>] ? recalc_sigpending+0x17/0x30
[  233.753491]  [<ffffffff81076437>] ? __set_task_blocked+0x37/0x80
[  233.753493]  [<ffffffff8107887f>] ? __set_current_blocked+0x3f/0x60
[  233.753495]  [<ffffffff8115b77c>] SyS_ioctl+0x4c/0x90
[  233.753496]  [<ffffffff81078add>] ? SyS_rt_sigprocmask+0x8d/0xb0
[  233.753500]  [<ffffffff8152e6d7>] entry_SYSCALL_64_fastpath+0x12/0x6a
[  233.753501] ---[ end trace c24109ba1fac09a6 ]---
Comment 1 Chris Wilson 2015-12-22 20:21:31 UTC 
Created attachment 120652 [details]
dmesg
Comment 2 Chris Wilson 2016-02-03 11:05:57 UTC 
Still in

commit 02932377a975a59ccd83095816d5b23183107d79
Author: Matt Roper <matthew.d.roper@intel.com>
Date:   Tue Feb 2 17:54:55 2016 -0800

    drm-intel-nightly: 2016y-02m-03d-01h-54m-27s UTC integration manifest
Comment 3 Maarten Lankhorst 2016-04-26 07:23:56 UTC 
Do you have a full log with drm.debug=0x1f?
Comment 4 Chris Wilson 2016-04-26 13:04:55 UTC 
Created attachment 123272 [details]
drm.debug=0x1f dmesg
Comment 5 Maarten Lankhorst 2016-05-03 08:07:40 UTC 
In intel_crt.c:

	if (HAS_PCH_LPT(dev))
		pipe_config->pipe_bpp = 24;

Can you make it a WARN_ON, see if it trips?
Comment 6 Chris Wilson 2016-05-03 08:30:54 UTC 
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index a2a31fd..64fe69d 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -261,8 +261,13 @@ static bool intel_crt_compute_config(struct intel_encoder *encoder,
                pipe_config->has_pch_encoder = true;
 
        /* LPT FDI RX only supports 8bpc. */
-       if (HAS_PCH_LPT(dev))
+       if (HAS_PCH_LPT(dev)) {
+               if (pipe_config->bw_constrained && pipe_config->pipe_bpp < 24) {
+                       DRM_DEBUG_KMS("LPT only supports 24bpp\n");
+                       return false;
+               }
                pipe_config->pipe_bpp = 24;
+       }
 
        /* FDI must always be 2.7 GHz */
        if (HAS_DDI(dev))

makes it fail silently. This setup (using a 1080p mode on a forced VGA output) used to work on this machine for all intents and purposes.
Comment 7 Chris Wilson 2016-05-03 08:40:35 UTC 
Replaced the modeline with the one from the edid (I guess I used cvt or gtf) and I can use the machine again. So what's the verdict on this where the setup used to work but now doesn't?
Comment 8 Jani Nikula 2016-05-03 09:56:33 UTC 
Bisect would probably be helpful?
Comment 9 Maarten Lankhorst 2016-05-04 10:41:19 UTC 
Did you generate the cvt line with -r ?
Comment 10 Chris Wilson 2016-05-04 11:37:08 UTC 
It had been working for so long, I can't remember its origins.
Comment 11 Maarten Lankhorst 2016-10-12 11:11:38 UTC 
commit f58a1acc7e4a1f37d26124ce4c875c647fbcc61f
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue May 3 10:33:01 2016 +0200

    drm/i915: Bail out of pipe config compute loop on LPT

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