Fix DSI display functionality on RPi5

[CaWeissWz]

Description

Fix Raspberry Pi 5 DSI functionality.

Context:

A display connected to the DSI connector of Raspberry Pi 5 does not work.
Dmesg reveals the following information:

[ 13.283052] mipi-dsi 1f00118000.dsi.0: deferred probe pending: mipi-dsi: supplier 2.reg_bridge not ready
[ 13.283060] platform 1.panel_disp: deferred probe pending: platform: wait for supplier /axi/pcie@120000/rp1/i2c@88000/reg_display@45

The problem could be traced back to a missing I2C Driver.
See: https://forum.armbian.com/topic/50963-dsi-display-does-not-work-on-raspberry-pi-5/

Documentation summary for feature / change

Add module to kernel configuration: CONFIG_I2C_DESIGNWARE_CORE

How Has This Been Tested?

Local build of armbian bookworm minimal and test if DSI display works

• [OK] kernel linux-bcm2711-current
• [fail] kernel linux-bcm2711-edge
• [fail] kernel linux-bcm2711-legacy

Both edge and legacy images failed to build, but the failure seems unrelated to the change.

Checklist:

Please delete options that are not relevant.

• [not applicable] My code follows the style guidelines of this project
• [OK] I have performed a self-review of my own code
• [not applicable] I have commented my code, particularly in hard-to-understand areas
• [OK] My changes generate no new warnings
• [not applicable] Any dependent changes have been merged and published in downstream modules

[coderabbitai]

Walkthrough

The changes add support for the DesignWare I2C core driver as a loadable module (CONFIG_I2C_DESIGNWARE_CORE=m) and enable I2C slave mode support (CONFIG_I2C_SLAVE=y) along with the DesignWare I2C slave driver (CONFIG_I2C_DESIGNWARE_SLAVE=y) as built-in in three bcm2711 platform kernel configuration files. No existing configuration options were removed or altered.

Suggested labels

ready to merge

Suggested reviewers

• EvilOlaf
• igorpecovnik

---

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Reviewing files that changed from the base of the PR and between a093e35 and 7c83b39.

📒 Files selected for processing (1)

• config/kernel/linux-bcm2711-legacy.config (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• config/kernel/linux-bcm2711-legacy.config

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

config/kernel/linux-bcm2711-current.config (1)

874-874: Verify module vs built-in configuration for I2C_DESIGNWARE_CORE

The DesignWare I2C core driver is currently set as a module (m). For CSI display on RPi5, early I2C availability at boot may be critical—ensure this module is auto-loaded before any dependent camera/display drivers initialize. Consider building it-in (y) if boot-time loading is unreliable.

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1540733 and 33f25cd.

📒 Files selected for processing (3)

• config/kernel/linux-bcm2711-current.config (1 hunks)
• config/kernel/linux-bcm2711-edge.config (1 hunks)
• config/kernel/linux-bcm2711-legacy.config (1 hunks)

🔇 Additional comments (4)

config/kernel/linux-bcm2711-edge.config (2)

859-859: Enable CONFIG_I2C_DESIGNWARE_CORE as module
Matches the other bcm2711 configurations in this PR, allowing the DesignWare I2C core driver to be loaded dynamically.

---

864-864: Enable CONFIG_I2C_SLAVE built-in
Consistent with the edge and legacy variants, this enables I2C slave support at build time.

config/kernel/linux-bcm2711-legacy.config (2)

817-817: Enable CONFIG_I2C_DESIGNWARE_CORE as module
Aligned with the edge configuration, this adds support for the DesignWare I2C core driver as a loadable module.

---

822-822: Enable CONFIG_I2C_SLAVE built-in
In line with other bcm2711 configs, this turns on I2C slave functionality at compile time.

[EvilOlaf]

Providing logs for failed builds would be neat...

[CaWeissWz]

Providing logs for failed builds would be neat...

Here are the logs of the edge kernel build:
log-build-f989a1c2-5029-47fe-948c-5bd0d60e195d.log

Unfortunately, the logs of the legacy kernel build are lost. I will re-try the build and post the logs on monday.

[EvilOlaf]

Please use either SHARE_LOG=yes or one of the curl commands provided at the end of each build run to upload logs manually to a random paste server. They'll include highlighting for those and make it overall easier to read them.

[EvilOlaf]

Seems like the build failure is unrelated to the suggested change but for some reason apt update failed within chroot:

--> (10430) COMMAND: DEBIAN_FRONTEND=noninteractive apt-get -y -q -o Dpkg::Use-Pty=0 -o APT::Get::List-Cleanup=0 update
   -->--> command failed with error code 100 after 9 seconds
--> (10439) WARNING: stacktrace for failed command [ exit code 100:chroot /home/carsten/Workspace/armbian/build/.tmp/rootfs-f989a1c2-5029-47fe-948c-5bd0d60e195d /usr/bin/env bash -e -o pipefail -c DEBIAN_FRONTEND=noninteractive apt-get -y -q -o Dpkg::Use-Pty=0 -o APT::Get::List-Cleanup=0 update

[EvilOlaf]

@coderabbitai isn't CONFIG_I2C_DESIGNWARE_SLAVE=ymissing in legacy and edge too?

[coderabbitai]

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🧩 Analysis chain

@EvilOlaf, let me check the configuration files to verify this observation.

---

🏁 Script executed:

#!/bin/bash
echo "=== Checking CONFIG_I2C_DESIGNWARE_SLAVE in all three bcm2711 kernel configs ==="
echo ""
echo "linux-bcm2711-current.config:"
grep "CONFIG_I2C_DESIGNWARE_SLAVE" config/kernel/linux-bcm2711-current.config || echo "Not found"
echo ""
echo "linux-bcm2711-edge.config:"
grep "CONFIG_I2C_DESIGNWARE_SLAVE" config/kernel/linux-bcm2711-edge.config || echo "Not found"
echo ""
echo "linux-bcm2711-legacy.config:"
grep "CONFIG_I2C_DESIGNWARE_SLAVE" config/kernel/linux-bcm2711-legacy.config || echo "Not found"
echo ""
echo "=== Checking all I2C_DESIGNWARE related configs ==="
echo ""
echo "linux-bcm2711-current.config:"
grep "CONFIG_I2C_DESIGNWARE" config/kernel/linux-bcm2711-current.config
echo ""
echo "linux-bcm2711-edge.config:"
grep "CONFIG_I2C_DESIGNWARE" config/kernel/linux-bcm2711-edge.config
echo ""
echo "linux-bcm2711-legacy.config:"
grep "CONFIG_I2C_DESIGNWARE" config/kernel/linux-bcm2711-legacy.config

Length of output: 1395

---

@EvilOlaf, you're absolutely correct! The verification shows that CONFIG_I2C_DESIGNWARE_SLAVE=y is indeed missing from both the edge and legacy configurations:

Current status:

• ✅ linux-bcm2711-current.config: Has both CONFIG_I2C_DESIGNWARE_CORE=m and CONFIG_I2C_DESIGNWARE_SLAVE=y
• ❌ linux-bcm2711-edge.config: Only has CONFIG_I2C_DESIGNWARE_CORE=m (missing CONFIG_I2C_DESIGNWARE_SLAVE=y)
• ❌ linux-bcm2711-legacy.config: Only has CONFIG_I2C_DESIGNWARE_CORE=m (missing CONFIG_I2C_DESIGNWARE_SLAVE=y)

This inconsistency should be addressed. If the DSI display functionality requires both configuration options for proper operation, then the edge and legacy kernel configurations are incomplete and may not work correctly. The CONFIG_I2C_DESIGNWARE_SLAVE=y option should be added to both edge and legacy configurations to ensure consistent behavior across all kernel variants.

    🐰
   ( o.o )
    > ^ <
*curious ears*

[EvilOlaf]

Did manual tests for current and edge using kernel-config and it is selected automatically this way. So yeah, @CaWeissWz please either verify it works as it is or address accordingly.

[CaWeissWz]

Please use either SHARE_LOG=yes or one of the curl commands provided at the end of each build run to upload logs manually to a random paste server. They'll include highlighting for those and make it overall easier to read them.

OK, here are the logs for the legacy kernel:
https://paste.armbian.com/pahidusidi

[CaWeissWz]

The initial 'current' image I testet did not have the CONFIG_I2C_DESIGNWARE_SLAVE config set, but DSI had worked for me.
Nevertheless, I added the config line in question for all 3 configurations, just to be save. I guess that it won't hurt either.

[wwortel]

Would it be possible to change the title of this PR into 'Fix DSI display functionality on RPi5'. The C in CSI is about interfacing camera signals, not applicable here. This PR is about interfacing certain screens that combine the MIPI DSI and I2C buses on one flexible flat cable and use the I2C bus to register and initialize the MIPI DSI bus, sometimes combined with touch screen communication via I2C.

[CaWeissWz]

Would it be possible to change the title of this PR into 'Fix DSI display functionality on RPi5'. The C in CSI is about interfacing camera signals, not applicable here. This PR is about interfacing certain screens that combine the MIPI DSI and I2C buses on one flexible flat cable and use the I2C bus to register and initialize the MIPI DSI bus, sometimes combined with touch screen communication via I2C.

You're absolutely right, this was a typo.