I R A Darth Aggie  wrote:
> On Sun, 1 Mar 2020 16:57:18 +0000 (UTC),
> bob prohaska , in
>  wrote:
>>  Is there some special trick that will make a Dell ST2220L HDMI
>>  monitor go to sleep when using the default GL driver on Buster?
>>
>>  With stretch the same thing happened, but the experimental GL
>>  driver put the monitor to sleep and woke it successfully. On
>>  Buster, the default GL driver seems to work well enough and is
>>  more stable than the (faster) experimental. But, even though
>>  the blanker seems to work, the monitor stays powered on.
>>
>>  There are numerous reports on-line of the ST2220L refusing to
>>  wake up, but I've not found any references to chronic insomnia.
>>
>>  I gather there are commands to put in config.txt, but it seems
>>  wise to ask before tampering.
>
> Arch has some of the best docs in the world. Some light reading when
> you have insomnia:
>
> https://wiki.archlinux.org/index.php/Display_Power_Management_Signaling
>
> Scrolling down, we see xset commands and their descriptions:
>
> Command                  Description
> xset s off               Disable screen saver blanking
> xset s 3600 3600         Change blank time to 1 hour
> xset -dpms               Turn off DPMS
> xset s off -dpms         Disable DPMS and prevent screen from blanking
> xset dpms force off      Turn off screen immediately
> xset dpms force standby  Standby screen
> xset dpms force suspend  Suspend screen
>
> But you probably need to run
>
> xset q
>
> to see your current settings. Thanks for the question, since I saw the
> section on how to modify settings for a given tty, as some of my
> servers don't blank the screen. I've been just hitting the power switch.

Using xset q I get:

eyboard Control:
  auto repeat:  on    key click percent:  0    LED mask:  00000000
  XKB indicators:
    00: Caps Lock:   off    01: Num Lock:    off    02: Scroll Lock: off
    03: Compose:     off    04: Kana:        off    05: Sleep:       off
    06: Suspend:     off    07: Mute:        off    08: Misc:        off
    09: Mail:        off    10: Charging:    off    11: Shift Lock:  off
    12: Group 2:     off    13: Mouse Keys:  off
  auto repeat delay:  500    repeat rate:  30
  auto repeating keys:  00ffffffdffffbbf
                        fadfffefffedffff
                        9fffffffffffffff
                        fff7ffffffffffff
  bell percent:  50    bell pitch:  400    bell duration:  100
Pointer Control:
  acceleration:  20/10    threshold:  10
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  600    cycle:  600
Colors:
  default colormap:  0x20    BlackPixel:  0x0    WhitePixel:  0xffffff
Font Path:
  /usr/share/fonts/X11/100dpi/:unscaled,/usr/share/fonts/X11/100dpi,built-ins
DPMS (Energy Star):
  Standby: 600    Suspend: 600    Off: 600
  DPMS is Enabled
  Monitor is On

I don't see anything obviously amiss: it looks like energy saving
behavior is on, though it's a little odd to have standby, suspend
and off with the same timing. Could the three states somehow conflict
with one another? With the "experimental GL " driver the screen
turns off as desired. Alas, the machine locks up without worning.

There seem to be two broad classes of monitors, CEA and DMT. I've been
letting Raspbian sniff out its own settings. Might forcibly setting
the display mode make a difference?

Thanks very much for your reply!

bob prohaska

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