I was hesitant to install the daily build again since I felt I was being
run around in circles. An acquaintance has pointed out that doing it
would server a useful purpose.
So I have completed that task. Once again I was unable to reproduce the
issue with a live-usb containing the daily build. There were occasions
when I thought the screen was going to go black - but then it did
recover. And once again I did try a live-usb with 14.04.1 and was also
not able to reproduce the issue: making me once again consider that it
might be a configuration issue.
So I looked at the parameters being used by the i915 driver.
These parameters were in common between the my system and the 14.04.1
live-usb that works so well:
/sys/module/i915/parameters/disable_power_well:1
/sys/module/i915/parameters/fastboot:N
/sys/module/i915/parameters/invert_brightness:0
/sys/module/i915/parameters/lvds_channel_mode:0
/sys/module/i915/parameters/lvds_downclock:0
/sys/module/i915/parameters/lvds_use_ssc:-1
/sys/module/i915/parameters/modeset:-1
/sys/module/i915/parameters/panel_ignore_lid:1
/sys/module/i915/parameters/powersave:1
/sys/module/i915/parameters/prefault_disable:N
/sys/module/i915/parameters/preliminary_hw_support:1
/sys/module/i915/parameters/reset:Y
/sys/module/i915/parameters/semaphores:-1
/sys/module/i915/parameters/vbt_sdvo_panel_type:-1
/sys/module/i915/parameters/enable_ips:1
/sys/module/i915/parameters/enable_psr:0
/sys/module/i915/parameters/enable_hangcheck:Y
These parameters seem to have been renamed:
/sys/module/i915/parameters/enable_rc6:1
/sys/module/i915/parameters/enable_fbc:-1
/sys/module/i915/parameters/enable_ppgtt:1
/* Power Saving features? */
/sys/module/i915/parameters/enable_pc8:1
/sys/module/i915/parameters/pc8_timeout:5000
/* Defunct LVDS setting? *?
/sys/module/i915/parameters/fbpercrtc:0
/* New parameters? */
/sys/module/i915/parameters/disable_display:N
/sys/module/i915/parameters/disable_vtd_wa:N
/sys/module/i915/parameters/enable_cmd_parser:1
I tried to change some of these at bootup to see if they affected the
behaviour: they didn't.
It seems possibly tied to power saving: on the 14.04.1 live-usb
buffering seemed to work better on user switching so perhaps the system
never though it was entering a power saving mode and thus never turned
off the screen.
Next week I will install the HWE Stack for 14.04.3 that has the Vivid
kernel/drivers to see if that fixes things.
My acquaintance is a retired software engineer - application level stuff
on Windows and Macs. But has played with Linux a bit and even though he
has never dug into drivers or kernel code he has said he would be
willing to help me out (already showed me how to build the kernel). So
I'll up my level interest in debugging.
What next steps do you suggest?
** Changed in: xorg (Ubuntu)
Status: Incomplete => New
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https://bugs.launchpad.net/bugs/1437719
Title:
[Dell Inspiron 5547] Black Screen on user switch
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