Hi Luca, Am Freitag, 20. März 2026, 11:46:11 CET schrieb Luca Ceresoli: > This series modernizes the i.mx8mp LCDIF driver to use the > bridge-connector, which is the current best practice in DRM. > > == Call for testing on i.MX8MP boards (especially those using HDMI)! > > This series applies changes to how video output devices are probed on > i.MX8MP, especially those using HDMI. Even though I have put care in not > breaking anything, there could potentially be pitfalls I haven't realized, > causing regressions on existing boards. > > I have thus added in Cc all developers which appeared active on dts files > for imx8mp boards involving video. I would appreciate testing on as many > boards as possible, along with a Tested-by tag, or a report about any > issues encountered. > > Thanks in advance to all testers!
For the whole series: Tested-by: Alexander Stein <[email protected]> # TQMa8MPxL/MBa8MPxL Because this platform falls into type A of patch 7 DRM_IMX8MP_DW_HDMI_BRIDGE_CONNECTOR_FIXUP has been disabled for me. Best regards, Alexander > > == Review recommendation > > I recommend reviewing patches in this order to be understood more > effectively: > > * Cover letter > * Patches 1-5 are small preliminary cleanups/improvements > * Patch 8 is the goal of this series, but would not work alone > * Patch 7 this lets patch 8 work; but in turn it can't work alone > * Patch 6 lets patch 7 work > > == Series description > > This series is not strictly related to DRM bridge hotplug, it is rather a > preparation step. Introducing hotplug would need two different approaches: > one for the new way, for drivers using bridge-connector and > DRM_BRIDGE_ATTACH_NO_CONNECTOR, another for drivers using the "old, legacy > way" where the last bridge is supposed to instantiate the > drm_connector. Hotplug is complicated enough in one case, so it makes sense > to only support the new way. > > The hardware I'm working on is an i.MX8MP, whose LCDIF driver is still > using the old way. So this series converts to the new way as a preparation > step. > > Patch 8 does the conversion, which is simple. However this would introduce > a regression on some boards. Here's why: > > There are 3 instances of the LCDIF in i.MX8MP: > > * LCDIF1, driving the DSI output > * LCDIF2, driving the LVDS output > * LCDIF3, driving the HDMI output > > The device drivers of peripherals connected to LCDIF1 and LCDIF2 already > support the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag. So far so good. > > LCDIF3 is more tricky. The HDMI pipeline is: > > LCDIF3 -> fsl,imx8mp-hdmi-pvi -> fsl,imx8mp-hdmi-tx -> HDMI connector > > The fsl,imx8mp-hdmi-tx (hdmi-tx) component supports both cases (with or > without DRM_BRIDGE_ATTACH_NO_CONNECTOR), but in the > DRM_BRIDGE_ATTACH_NO_CONNECTOR case it does not create a drm_connector, > thus preventing the creation of the pipeline. To make it work a connector > must be created, and the way to do so is describing the connector in the > device tree (compatible = "hdmi-connector"), so the display-driver will add > the connector along with a wrapping bridge. > > Unfortunately not all device trees in mainline have an hdmi-connector > node. Adding one is easy, but would break existing hardware upgrading to a > newer kernel without upgrading the device tree blob. This is addressed by > patch 7 reusing an existing approach to add such a node to the live device > tree at init time using a device tree overlay for boards which don't have > one. > > Finally, patch 7 cannot work alone because of a bad interaction between > devlink and device tree overlays. Patch 6 solves that. > > == Grand plan > > This is part of the work to support hotplug of DRM bridges. The grand plan > was discussed in [0]. > > Here's the work breakdown (➜ marks the current series): > > 1. … add refcounting to DRM bridges struct drm_bridge, > based on devm_drm_bridge_alloc() > A. ✔ add new alloc API and refcounting (v6.16) > B. ✔ convert all bridge drivers to new API (v6.17) > C. ✔ kunit tests (v6.17) > D. ✔ add get/put to drm_bridge_add/remove() + attach/detach() > and warn on old allocation pattern (v6.17) > E. … add get/put on drm_bridge accessors > 1. ✔ drm_bridge_chain_get_first_bridge(), add cleanup action (v6.18) > 2. ✔ drm_bridge_get_prev_bridge() (v6.18) > 3. ✔ drm_bridge_get_next_bridge() (v6.19) > 4. ✔ drm_for_each_bridge_in_chain() (v6.19) > 5. ✔ drm_bridge_connector_init (v6.19) > 6. … protect encoder bridge chain with a mutex > 7. … of_drm_find_bridge > a. ✔ add of_drm_get_bridge() (v7.0), > convert basic direct users (v7.0-v7.1) > b. ✔ convert direct of_drm_get_bridge() users, part 2 (v7.0) > c. ✔ convert direct of_drm_get_bridge() users, part 3 (v7.0) > d. ✔… convert direct of_drm_get_bridge() users, part 4 > (some v7.1, some pending) > e. convert bridge-only drm_of_find_panel_or_bridge() users > 8. drm_of_find_panel_or_bridge, *_of_get_bridge > 9. ✔ enforce drm_bridge_add before drm_bridge_attach (v6.19) > F. ✔ debugfs improvements > 1. ✔ add top-level 'bridges' file (v6.16) > 2. ✔ show refcount and list lingering bridges (v6.19) > 2. … handle gracefully atomic updates during bridge removal > A. ✔ Add drm_bridge_enter/exit() to protect device resources (v7.0) > B. … protect private_obj removal from list > C. ✔ Add drm_bridge_clear_and_put() (v7.1) > 3. … DSI host-device driver interaction > 4. ✔ removing the need for the "always-disconnected" connector > 5. ➜ Migrate i.MX LCDIF driver to bridge-connector > 6. DRM bridge hotplug > A. Bridge hotplug management in the DRM core > B. Device tree description > > [0] > https://lore.kernel.org/lkml/[email protected]/#t > > Signed-off-by: Luca Ceresoli <[email protected]> > --- > Luca Ceresoli (8): > drm/mxsfb/lcdif: simplify remote pointer management using __free > drm/mxsfb/lcdif: don't unnecessarily loop over ports > drm/mxsfb/lcdif: use dev_err_probe() consistently in lcdif_attach_bridge > drm/bridge: dw-hdmi: document the output_port field > drm/bridge: dw-hdmi: warn on unsupported attach combination > drm/bridge: dw-hdmi: move next_bridge lookup to attach time > drm/bridge: imx8mp-hdmi-tx: add an hdmi-connector when missing using a > DT overlay at boot time > drm/mxsfb/lcdif: use DRM_BRIDGE_ATTACH_NO_CONNECTOR and the > bridge-connector > > drivers/gpu/drm/bridge/imx/Kconfig | 17 +++++ > drivers/gpu/drm/bridge/imx/Makefile | 2 + > .../bridge/imx/imx8mp-hdmi-tx-connector-fixup.c | 60 +++++++++++++++ > .../bridge/imx/imx8mp-hdmi-tx-connector-fixup.dtso | 38 ++++++++++ > drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c | 1 + > drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 45 ++++------- > drivers/gpu/drm/mxsfb/Kconfig | 1 + > drivers/gpu/drm/mxsfb/lcdif_drv.c | 88 > +++++++++------------- > include/drm/bridge/dw_hdmi.h | 5 ++ > 9 files changed, 174 insertions(+), 83 deletions(-) > --- > base-commit: 8402cf4fc8f8d5756dc81cf9fda1dccdb3622634 > change-id: 20260306-drm-lcdif-dbanc-83dd948327de > > Best regards, > -- TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht München, HRB 105018 Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider http://www.tq-group.com/
