ED-HMI2220-070C: black screen with stock driver bridge-init value 0x02; 0x01 restores display on affected unit

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Bewertung

Schwierigkeit
4/5
Geschätzter Aufwand
3-5 Tage
Anfängerfreundlichkeit
45/100
Issue-Typ
Bug
Klarheit
Größtenteils klar
Aktivitätsstatus
Aktiv
Tech-Stack
c, linux
Bereich
embedded-iot, operating-systems

Rechercherichtung

Start with drivers/regulator/edatec-panel-regulator.c and inspect the REG_BRIDGE_INIT write alongside the device-tree overlay configuration and the reported I2C values. Compare behavior across affected and unaffected panel units or controller revisions to determine how the initialization value should be selected. Done means the affected display works after a cold boot while supported units retain working displays; add or run relevant regulator and panel tests if available.

Vom Indexierungsmodell aus dem Issue-Text verfasst.

Beschreibung

Describe the bug

When installing and operating system, such as the latest Raspberry Pi OS release.
The HMI will be blank. The HDMI port will work. The HMI will not.

Steps to reproduce the behaviour

reinstall an os,
Or, after applying work around, unapply work around. same behavior.
Issue may be present in certain specific versions

Device (s)

Ed-HMI2220-070c

System

pi@raspberrypi:~ $ cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 13 (trixie)"
NAME="Debian GNU/Linux"
VERSION_ID="13"
VERSION="13 (trixie)"
VERSION_CODENAME=trixie
DEBIAN_VERSION_FULL=13.7
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

$ uname -a
Linux raspberrypi 6.18.50+rpt-rpi-v8 #1 SMP PREEMPT Debian 1:6.18.50-1+rpt1 (2026-09-11) aarch64 GNU/Linux
pi@raspberrypi:~ $ vcgencmd version
Sep 14 2026 14:49:30
Copyright (c) 2012 Broadcom
version a86983925695a7e63166327d7c002d64040ed31d (clean) (release) (start)
pi@raspberrypi:~ $ cat /etc/rpi-issue
Raspberry Pi reference 2026-10-06
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, b2cd98a9ee08a31ef7d0110ed09f2492bbd972ec, stage4

Logs

No response

Additional context

This issue may pertain to the 8GB or older models of the ED-HMI2220-070C
From testing, the 32GB model is unaffected.

Environment:

  • Hardware: EDATEC ED-HMI2220-070C, unit with 8 GB eMMC storage
  • OS: Debian GNU/Linux 13 (Trixie), using Raspberry Pi kernel packages
  • Kernel: 6.18.50+rpt-rpi-v8
  • Driver: edatec_panel_regulator
  • Default overlay configuration
dtoverlay=vc4-kms-v3d

[all]
dtoverlay=vc4-kms-dsi-edatec-panel-070c,interrupt=7

I followed EDATEC application notes, which describes support through the stock Raspberry Pi kernel and overlays.

Expected Behavior:

The built-in display shows the console and desktop after boot.

Actual beahvior:

The backlight turns on, but the screen remains black. HDMI output works.
The kernel reports DSI-1 as connected and enabled at 1024×600.

workaround

enable userspace i2c
sudo i2ctransfer -f -y 10 w2@0x27 0x11 0x01
Desktop appears instantly

suspected source Issue:

https://github.com/raspberrypi/linux/blob/rpi-6.18.y/drivers/regulator/edatec-panel-regulator.c
regmap_write(regmap, REG_BRIDGE_INIT, 0x02);
is evidently incorrect for this unit model.

repeatability:

sudo i2ctransfer -f -y 10 w2@0x27 0x11 0x02
setting the value back to its initial setting will reproduce the issue, if the HMI is fully powered off, then restarted. simply running the command will not produce the initial behavior.

Proposal for resolution:

Please investigate whether the bridge-initialization value needs to be selected according to the panel-controller revision or exposed through a device-tree property, rather than fixed at 0x02 for all supported units.

I only have 8GB and 32GB models of this device, and I am not saying there is some correlation between disk space and video driver issues. This issue may effect various unit models, older or newer models, I'm not really sure. The ones with the blue label, maybe that indicates something relevant to the appropriate person. I have not compiled a specific hardware variants list that might compare hardware differences, or versions of this device, and the device itself is not clearly labeled. All I can verify is that I have some 8GB models of The Ed-HMI2220-070c device, and they are effected by this condition.

Reference Material:

https://edatec.cn/docs/an/an44-use-7-inch-and-10.1-inch-hmi-on-standard-rpi-os/#_2-2-configuration-instructions

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