[mario74m]

I have a problem with a fresh LibreELEC installation on Raspberry Pi 3, which is connected to a Sony Bravia KDL-50W828B TV via HDMI.

In a nutshell, when Kodi boots, everything is OK, the TV switches to the correct input (which is HDMI 2) automatically. However, when it goes to sleep after a period of inactivity, trying to wake Kodi up by remote control buttons doesn't turn on the screen anymore. Furthermore, it also happens immediately after powering on, while the device hasn't yet had a chance to go to sleep - changing the TV input from HDMI2 to something else and then immediately back again renders a black screen.

I have been able to reproduce the behaviour by controlling Kodi through a ssh shell. First, with the Kodi GUI displayed normally on the TV screen, I type "tvservice -o", and the screen goes blank. After that, typing "tvservice -p" changes the HDMI status (obtained by "tvservice -s") from "HDMI off" to "HDMI in HDMI mode" but the screen remains blank nevertheless. The only way to get the image back is restarting the Kodi service by "systemctl stop kodi" followed by "systemctl start kodi", or power cycling the RPI, which is not exactly the user friendliest way.

I fiddled with /flash/config.txt settings dealing with HDMI, but to no amount - whatever I change, the result remains the same. I also tried changing the CEC service configuration HDMI parameters with the same results.

Could there be anything else I could try?

[Klojum]

Try change the HDMI port number in the Input CEC section. Make it '2' instead of the default '0'

[elpa02]

In order to avoid opening a similar thread i write down in here my case hoping to help me figure out whats going on with my tv.

I have made a fresh installation of 17.3 Kodi over latest LibreELEC on Raspberry Pi 3, which is connected to a LG 42LE5500.
In any attempt i get a "no signal" message from the very beggining. I have tried only all 4 LG's HDMI connections and i ve tried power on rasp pi3 before LG is on, after, on standby etc.

(Before that i had made almost the same as follows over Xbian.)
Since with its default config file didn't play i've tried many hacks combinations  found in different forums with no success like:
hdmi_ignore_cec_init=1
hdmi_force_hotplug=1
hdmi_boost=4,5,6,7 till 9
hdmi_safe=1 (alone)

Then i made a SSH connection and run tvservice for both DMT and CEA modes and i was returned that the LG plays both. CEAs are many more with native mode 4 and prefered one mode 16. After that i add some lines in config
config_hdmi_boost=7
hdmi_group=1
hdmi_mode=4 (and hdmi_mode=16)
but still no signal.

I would like to point out here that in each attempt LG recognises the hdmi where Rasp is connected to and in the case that LG was in standby mode it switches on automatically to the correct hdmi input showing the simplink logo but stiil no signal.
Any help is appreciated

PS. I've tried different cables and monitors. On a LG pc monitor W2361V and on a Samsung 50UE6500 everything works fine with the same cables , CEC functions etc.

[popcornmix]

In a nutshell, when Kodi boots, everything is OK, the TV switches to the correct input (which is HDMI 2) automatically. However, when it goes to sleep after a period of inactivity

Please be specific. Is this kodi or TV going to sleep?
Kodi by default won't sleep. There is a screensaver which probably defaults to "dim" (dim, but gui still visible). You might want to disable screensaver in gui to rule its effect out.

trying to wake Kodi up by remote control buttons doesn't turn on the screen anymore.

I'd like to know if the display is blank or kodi it no longer responding to remote (I assume CEC?) presses. Use an alternate remote (e.g. physical keyboard or smart phone remote) to confirm which it is.

I have been able to reproduce the behaviour by controlling Kodi through a ssh shell. First, with the Kodi GUI displayed normally on the TV screen, I type "tvservice -o", and the screen goes blank. After that, typing "tvservice -p" changes the HDMI status (obtained by "tvservice -s") from "HDMI off" to "HDMI in HDMI mode" but the screen remains blank nevertheless.

That is expected behaviour. Kodi won't continue to run after having the display system yanked out.