<html>
    <head>
      <base href="https://bugs.freedesktop.org/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [drm:drm_calc_timestamping_constants [drm]] *ERROR* crtc 21: Can't calculate constants, dotclock = 0!"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=92580">92580</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[drm:drm_calc_timestamping_constants [drm]] *ERROR* crtc 21: Can't calculate constants, dotclock = 0!
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>DRI
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>XOrg git
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>x86-64 (AMD64)
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux (All)
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>DRM/Intel
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>intel-gfx-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>ajb@elrepo.org
          </td>
        </tr>

        <tr>
          <th>QA Contact</th>
          <td>intel-gfx-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>intel-gfx-bugs@lists.freedesktop.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=119054" name="attach_119054" title="Complete dmesg file">attachment 119054</a> <a href="attachment.cgi?id=119054&action=edit" title="Complete dmesg file">[details]</a></span>
Complete dmesg file

Starting with linux-4.3-rc1 and through to the current 4.3-rc6 sources from
Linus' tree, the error message --

[drm:drm_calc_timestamping_constants [drm]] *ERROR* crtc 21: Can't calculate
constants, dotclock = 0!

-- followed by --

------------[ cut here ]------------
WARNING: CPU: 1 PID: 6 at drivers/gpu/drm/drm_atomic.c:491
drm_atomic_check_only+0x399/0x540 [drm]()
Modules linked in: ahci(+) libahci libata firewire_ohci(+) firewire_core
crc_itu_t yenta_socket(+) tg3 ptp pps_core i915(+) i2c_algo_bit drm_kms_helper
syscopyarea sysfillrect sysimgblt fb_sys_fops drm video
CPU: 1 PID: 6 Comm: kworker/u4:0 Not tainted 4.3.0-0.rc1.el7.elrepo.x86_64 #1
Hardware name: Dell Inc. Latitude E5500                  /0DW633, BIOS A19
06/13/2013
Workqueue: events_unbound async_run_entry_fn
 0000000000000000 0000000011057432 ffff88011abdfa10 ffffffff8131e6b0
 0000000000000000 ffff88011abdfa48 ffffffff8107ae96 ffff880037303000
 0000000000000000 0000000000000000 0000000000000000 ffff880037bfb600
Call Trace:
 [<ffffffff8131e6b0>] dump_stack+0x44/0x64
 [<ffffffff8107ae96>] warn_slowpath_common+0x86/0xc0
 [<ffffffff8107afda>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa002f529>] drm_atomic_check_only+0x399/0x540 [drm]
 [<ffffffffa002f7bd>] ? drm_atomic_set_fb_for_plane+0x2d/0x90 [drm]
 [<ffffffffa002f6e7>] drm_atomic_commit+0x17/0x60 [drm]
 [<ffffffffa014f3d5>] intel_get_load_detect_pipe+0x395/0x540 [i915]
 [<ffffffffa018671a>] intel_tv_detect+0x13a/0x570 [i915]
 [<ffffffff81530080>] ? i2c_transfer+0x60/0xb0
 [<ffffffffa016dc11>] ? intel_dp_detect+0x101/0x4f0 [i915]
 [<ffffffffa00a2d25>]
drm_helper_probe_single_connector_modes_merge_bits+0x2e5/0x4a0 [drm_kms_helper]
 [<ffffffffa00a2ef3>] drm_helper_probe_single_connector_modes+0x13/0x20
[drm_kms_helper]
 [<ffffffffa00ace6d>] drm_fb_helper_probe_connector_modes.isra.3+0x4d/0x70
[drm_kms_helper]
 [<ffffffffa00ae05a>] drm_fb_helper_initial_config+0x5a/0x3c0 [drm_kms_helper]
 [<ffffffff810156b2>] ? __switch_to+0x202/0x490
 [<ffffffffa015f44b>] intel_fbdev_initial_config+0x1b/0x20 [i915]
 [<ffffffff8109c0fa>] async_run_entry_fn+0x4a/0x140
 [<ffffffff8109302c>] process_one_work+0x14c/0x3c0
 [<ffffffff81093894>] worker_thread+0x114/0x470
 [<ffffffff81093780>] ? rescuer_thread+0x310/0x310
 [<ffffffff810993d8>] kthread+0xd8/0xf0
 [<ffffffff81099300>] ? kthread_park+0x60/0x60
 [<ffffffff816d02df>] ret_from_fork+0x3f/0x70
 [<ffffffff81099300>] ? kthread_park+0x60/0x60
---[ end trace a4f3b246a07cdefe ]---

-- and --

------------[ cut here ]------------
WARNING: CPU: 0 PID: 231 at drivers/gpu/drm/drm_atomic.c:491
drm_atomic_check_only+0x399/0x540 [drm]()
Modules linked in: iwldvm(+) iTCO_wdt mac80211 iTCO_vendor_support snd_timer
snd dell_wmi dell_rbtn dell_laptop gpio_ich sparse_keymap joydev sdhci_pci
sdhci input_leds ppdev dcdbas coretemp dell_smm_hwmon iwlwifi lpc_ich mmc_core
serio_raw kvm_intel pcspkr kvm wmi cfg80211 rfkill i2c_i801 mfd_core acpi_als
soundcore parport_pc 8250_fintek kfifo_buf industrialio parport shpchp
acpi_cpufreq xfs libcrc32c sr_mod cdrom sd_mod ahci libahci libata
firewire_ohci firewire_core crc_itu_t yenta_socket tg3 ptp pps_core i915
i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm
video
CPU: 0 PID: 231 Comm: kworker/0:3 Tainted: G        W      
4.3.0-0.rc1.el7.elrepo.x86_64 #1
Hardware name: Dell Inc. Latitude E5500                  /0DW633, BIOS A19
06/13/2013
Workqueue: events output_poll_execute [drm_kms_helper]
 0000000000000000 00000000fdb96593 ffff88003702ba10 ffffffff8131e6b0
 0000000000000000 ffff88003702ba48 ffffffff8107ae96 ffff880037303000
 0000000000000000 0000000000000000 0000000000000000 ffff8800d63f6200
Call Trace:
 [<ffffffff8131e6b0>] dump_stack+0x44/0x64
 [<ffffffff8107ae96>] warn_slowpath_common+0x86/0xc0
 [<ffffffff8107afda>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa002f529>] drm_atomic_check_only+0x399/0x540 [drm]
 [<ffffffffa002f7bd>] ? drm_atomic_set_fb_for_plane+0x2d/0x90 [drm]
 [<ffffffffa002f6e7>] drm_atomic_commit+0x17/0x60 [drm]
 [<ffffffffa014f3d5>] intel_get_load_detect_pipe+0x395/0x540 [i915]
 [<ffffffffa018671a>] intel_tv_detect+0x13a/0x570 [i915]
 [<ffffffff81530080>] ? i2c_transfer+0x60/0xb0
 [<ffffffffa00a2d25>]
drm_helper_probe_single_connector_modes_merge_bits+0x2e5/0x4a0 [drm_kms_helper]
 [<ffffffffa00a2ef3>] drm_helper_probe_single_connector_modes+0x13/0x20
[drm_kms_helper]
 [<ffffffffa00ace6d>] drm_fb_helper_probe_connector_modes.isra.3+0x4d/0x70
[drm_kms_helper]
 [<ffffffffa00adebe>] drm_fb_helper_hotplug_event+0x5e/0xe0 [drm_kms_helper]
 [<ffffffffa015f5ee>] intel_fbdev_output_poll_changed+0x1e/0x30 [i915]
 [<ffffffffa00a25d7>] drm_kms_helper_hotplug_event+0x27/0x30 [drm_kms_helper]
 [<ffffffffa00a26ad>] output_poll_execute+0x6d/0x1d0 [drm_kms_helper]
 [<ffffffff8109302c>] process_one_work+0x14c/0x3c0
 [<ffffffff81093894>] worker_thread+0x114/0x470
 [<ffffffff816cbdef>] ? __schedule+0x2af/0x8b0
 [<ffffffff81093780>] ? rescuer_thread+0x310/0x310
 [<ffffffff810993d8>] kthread+0xd8/0xf0
 [<ffffffff81099300>] ? kthread_park+0x60/0x60
 [<ffffffff816d02df>] ret_from_fork+0x3f/0x70
 [<ffffffff81099300>] ? kthread_park+0x60/0x60
---[ end trace a4f3b246a07cdeff ]---

-- are displayed.

Bisecting the kernel, the following "bad commit" is identified --

eddfcbcdc27fbecb33bff098967bbdd7ca75bfa6 is the first bad commit
commit eddfcbcdc27fbecb33bff098967bbdd7ca75bfa6
Author: Maarten Lankhorst <<a href="mailto:maarten.lankhorst@linux.intel.com">maarten.lankhorst@linux.intel.com</a>>
Date:   Mon Jun 15 12:33:53 2015 +0200

    drm/i915: Update less state during modeset.

    No need to repeatedly call update_watermarks, or update_fbc.
    Down to a single call to update_watermarks in .crtc_enable

    Signed-off-by: Maarten Lankhorst <<a href="mailto:maarten.lankhorst@linux.intel.com">maarten.lankhorst@linux.intel.com</a>>
    Reviewed-by: Matt Roper <<a href="mailto:matthew.d.roper@intel.com">matthew.d.roper@intel.com</a>>
    Tested-by(IVB): Matt Roper <<a href="mailto:matthew.d.roper@intel.com">matthew.d.roper@intel.com</a>>
    Signed-off-by: Daniel Vetter <<a href="mailto:daniel.vetter@ffwll.ch">daniel.vetter@ffwll.ch</a>>

:040000 040000 0b47d48b159bb87bff39ae05095746d487c04372
43ac83106c605cce79c28811014ac41dd9069af8 M      drivers</pre>
        </div>
      </p>
      <hr>
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