[Bug 91434] [IVB/HSW] 23.976Hz & 24Hz modes broken on dual-display with recent (4.0.x) kernels

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91434

--- Comment #52 from Martin Andersen <martin.x.andersen at gmail.com> ---
Ok, failing any word from Intel after the required debug output was provided
again for the n-th time, can it at least be acknowledged whether the option to
limit bpc is going to be implemented - see the link to the proposed patch below
- so this can at least be confirmed or ruled out once and for all –

https://www.spinics.net/lists/intel-gfx/msg143836.html ([RFC 1/2] drm/i915: Add
connector property to force bpc)

Currently there are no options relating to this for the i915 driver. Valid
options at the time of writing are as follows:



parm:           modeset:Use kernel modesetting [KMS] (0=disable, 1=on, -1=force
vga console preference [default]) (int)
parm:           panel_ignore_lid:Override lid status (0=autodetect,
1=autodetect disabled [default], -1=force lid closed, -2=force lid open) (int)
parm:           enable_dc:Enable power-saving display C-states. (-1=auto
[default]; 0=disable; 1=up to DC5; 2=up to DC6) (int)
parm:           enable_fbc:Enable frame buffer compression for power savings
(default: -1 (use per-chip default)) (int)
parm:           lvds_channel_mode:Specify LVDS channel mode (0=probe BIOS
[default], 1=single-channel, 2=dual-channel) (int)
parm:           panel_use_ssc:Use Spread Spectrum Clock with panels [LVDS/eDP]
(default: auto from VBT) (int)
parm:           vbt_sdvo_panel_type:Override/Ignore selection of SDVO panel
mode in the VBT (-2=ignore, -1=auto [default], index in VBT BIOS table) (int)
parm:           reset:Attempt GPU resets (0=disabled, 1=full gpu reset,
2=engine reset [default]) (int)
parm:           vbt_firmware:Load VBT from specified file under /lib/firmware
(charp)
parm:           error_capture:Record the GPU state following a hang. This
information in /sys/class/drm/card<N>/error is vital for triaging and debugging
hangs. (bool)
parm:           enable_hangcheck:Periodically check GPU activity for detecting
hangs. WARNING: Disabling this can cause system wide hangs. (default: true)
(bool)
parm:           enable_ppgtt:Override PPGTT usage. (-1=auto [default],
0=disabled, 1=aliasing, 2=full, 3=full with extended address space) (int)
parm:           enable_psr:Enable PSR (0=disabled, 1=enabled - link mode chosen
per-platform, 2=force link-standby mode, 3=force link-off mode) Default: -1
(use per-chip default) (int)
parm:           alpha_support:Enable alpha quality driver support for latest
hardware. See also CONFIG_DRM_I915_ALPHA_SUPPORT. (bool)
parm:           disable_power_well:Disable display power wells when possible
(-1=auto [default], 0=power wells always on, 1=power wells disabled when
possible) (int)
parm:           enable_ips:Enable IPS (default: true) (int)
parm:           fastboot:Try to skip unnecessary mode sets at boot time
(default: false) (bool)
parm:           prefault_disable:Disable page prefaulting for
pread/pwrite/reloc (default:false). For developers only. (bool)
parm:           load_detect_test:Force-enable the VGA load detect code for
testing (default:false). For developers only. (bool)
parm:           force_reset_modeset_test:Force a modeset during gpu reset for
testing (default:false). For developers only. (bool)
parm:           invert_brightness:Invert backlight brightness (-1 force normal,
0 machine defaults, 1 force inversion), please report PCI device ID, subsystem
vendor and subsystem device ID to dri-devel at lists.freedesktop.org, if your
machine needs it. It will then be included in an upcoming module version. (int)
parm:           disable_display:Disable display (default: false) (bool)
parm:           enable_cmd_parser:Enable command parsing (true=enabled
[default], false=disabled) (bool)
parm:           mmio_debug:Enable the MMIO debug code for the first N failures
(default: off). This may negatively affect performance. (int)
parm:           verbose_state_checks:Enable verbose logs (ie. WARN_ON()) in
case of unexpected hw state conditions. (bool)
parm:           nuclear_pageflip:Force enable atomic functionality on platforms
that don't have full support yet. (bool)
parm:           edp_vswing:Ignore/Override vswing pre-emph table selection from
VBT (0=use value from vbt [default], 1=low power swing(200mV),2=default
swing(400mV)) (int)
parm:           enable_guc:Enable GuC load for GuC submission and/or HuC load.
Required functionality can be selected using bitmask values. (-1=auto,
0=disable [default], 1=GuC submission, 2=HuC load) (int)
parm:           guc_log_level:GuC firmware logging level. Requires GuC to be
loaded. (-1=auto [default], 0=disable, 1..4=enable with verbosity min..max)
(int)
parm:           guc_firmware_path:GuC firmware path to use instead of the
default one (charp)
parm:           huc_firmware_path:HuC firmware path to use instead of the
default one (charp)
parm:           enable_dp_mst:Enable multi-stream transport (MST) for new
DisplayPort sinks. (default: true) (bool)
parm:           enable_dpcd_backlight:Enable support for DPCD backlight control
(default:false) (bool)
parm:           enable_gvt:Enable support for Intel GVT-g graphics
virtualization host support(default:false) (bool)

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