====== Mini PC Intel Pentium J3710 ======
===== Video card problem with kernel 6.12 =====
Using **Debian 13 Trixie** with **kernel 6.12.69**, the screen goes blank (no HDMI signal) as soon as it switches to frame buffer. With **dmesg** you can read the following errors:
[ 6.587061] i915 0000:00:02.0: [drm] timed out waiting for [ENCODER:98:HDMI B] port ready: got 0xf, expected 0x0
[ 16.775053] i915 0000:00:02.0: [drm] *ERROR* [CRTC:53:pipe A] flip_done timed out
[ 27.015096] i915 0000:00:02.0: [drm] *ERROR* flip_done timed out
[ 27.015122] i915 0000:00:02.0: [drm] *ERROR* [CRTC:53:pipe A] commit wait timed out
[ 37.255074] i915 0000:00:02.0: [drm] *ERROR* flip_done timed out
[ 37.255097] i915 0000:00:02.0: [drm] *ERROR* [CONNECTOR:99:HDMI-A-1] commit wait timed out
[ 47.495072] i915 0000:00:02.0: [drm] *ERROR* flip_done timed out
[ 47.495095] i915 0000:00:02.0: [drm] *ERROR* [PLANE:32:primary A] commit wait timed out
[ 57.735072] i915 0000:00:02.0: [drm] *ERROR* [CRTC:53:pipe A] flip_done timed out
[ 57.932964] i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device
The only way to boot Debian 13 with kernel 6.12 is to pass the **nomodeset** kernel parameter.
===== Kernel 6.1 =====
It is possible to install **kernel 6.1.0** from **Debian 12 Bookworm**, so that frame buffer works:
[ 5.399065] fbcon: i915drmfb (fb0) is primary device
[ 5.438998] Console: switching to colour frame buffer device 128x37
[ 5.458533] i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device
Despite the HDMI monitor is connected, the status pseudfile reports that it is **disconnected**:
cat /sys/class/drm/card0-HDMI-A-1/status
disconnected
Writing the **on** string to the file changes the status to connected:
echo on > /sys/class/drm/card0-HDMI-A-1/status
cat /sys/class/drm/card0-HDMI-A-1/status
connected
but it causes a kernel trace:
[ 69.315446] i915 0000:00:02.0: timed out waiting for [ENCODER:94:HDMI B] port ready: got 0xf, expected 0x0
When the **i915** kernel module is loaded, you can find five **DRM** (Direct Rendering Manager) devices managed by **card0**:
ls -1 /sys/class/drm/
card0
card0-DP-1
card0-DP-2
card0-HDMI-A-1
card0-HDMI-A-2
card0-HDMI-A-3
renderD128
version
It is possibile to do a **complete hardware reset** of the cards using the following command:
echo "0000:00:02.0" > /sys/bus/pci/drivers/i915/unbind
sleep 1
echo "0000:00:02.0" > /sys/bus/pci/drivers/i915/bind
After the //unbind// you can verify that the directory **/sys/class/drm/** is empty, it will be populated again after the //bind//.
===== Blanking the Virtual Terminal =====
When the host is started in frame buffer text console, the **setterm** command can be used to force the screen to go blank:
setterm --blank force
setterm --powerdown 0
The monitor turns off due no signal and remains blank even keys are pressed on the keyboard.
To revive the screen:
setterm --blank poke
setterm --powerdown 0
If the screen is blanked the following command returns **1**:
setterm --blank
1
==== DPMS (Display Power Management Signaling) ====
DPMS (Display Power Management Signaling) is a VESA standard used to reduce monitor power consumption by controlling power states (On, Standby, Suspend, Off) generally based on user inactivity.
It is possible to control the status of the display connected to the frame buffer writing some values to the pseudo file:
echo 4 > /sys/class/graphics/fb0/blank
echo 0 > /sys/class/graphics/fb0/blank
| 0 | FB_BLANK_UNBLANK | Screen ON (normal operation) |
| 1 | FB_BLANK_NORMAL | Blank screen (no power saving) |
| 2 | FB_BLANK_VSYNC_SUSPEND | Suspend vertical sync |
| 3 | FB_BLANK_HSYNC_SUSPEND | Suspend horizontal sync |
| 4 | FB_BLANK_POWERDOWN | Power down display (DPMS off) |
Writing the value 4 to the pseudodevice changes the **DPMS** property from **On=0** to **Off=3**. It is possibile to check all the **connectors properties** using **modetest** (provided by the **libdrm-tests** Debian package):
modetest -M i915 -c
opened device `Intel Graphics` on driver `i915` (version 1.6.0 at 20201103)
Connectors:
id encoder status name size (mm) modes encoders
95 94 connected HDMI-A-1 0x0 5 94
modes:
index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot
#0 1024x768 60.00 1024 1048 1184 1344 768 771 777 806 65000 flags: nhsync, nvsync; type: driver
#1 800x600 60.32 800 840 968 1056 600 601 605 628 40000 flags: phsync, pvsync; type: driver
...
2 DPMS:
flags: enum
enums: On=0 Standby=1 Suspend=2 Off=3
value: 3
....
107 106 connected HDMI-A-2 470x260 30 106
modes:
index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot
#0 1024x600 59.82 1024 1068 1156 1344 600 603 609 625 50250 flags: phsync, nvsync; type: preferred, driver
#1 1920x1080 60.00 1920 2008 2052 2200 1080 1084 1089 1125 148500 flags: phsync, pvsync; type: driver
...
2 DPMS:
flags: enum
enums: On=0 Standby=1 Suspend=2 Off=3
value: 3
....
FIXME What is this?
/usr/sbin/vbetool dpms on
/usr/sbin/vbetool dpms off
===== Pygame =====
We verified what driver uses the Pygame app:
import pygame
pygame.init()
print(pygame.display.get_driver())
It says **KMSDRM**.
Using that driver the SDL **Simple DirectMedia Layer** library owns the DRM master, external tools (modetest, sysfs) do not work for blanking the screen. The correct solution is to control this from inside SDL.
===== HDMI Monitor supported modes =====
cat /sys/class/drm/card0-HDMI-A-1/modes
1024x600
800x600
800x600
800x600
800x600
720x576
...
fbset -i -fb /dev/fb0
mode "1024x600"
geometry 1024 600 1024 600 32
timings 0 0 0 0 0 0 0
rgba 8/16,8/8,8/0,0/0
endmode
Frame buffer device information:
Name : i915drmfb
Address : 0
Size : 2457600
Type : PACKED PIXELS
Visual : TRUECOLOR
XPanStep : 1
YPanStep : 1
YWrapStep : 0
LineLength : 4096
Accelerator : No