[PATCH v7 02/12] drm: bridge: panel: Implement drmm_of_dsi_get_bridge helper

[Maxime Ripard]

On Wed, Mar 29, 2023 at 08:56:29PM +0530, Jagan Teki wrote:
> On Wed, Mar 29, 2023 at 8:33 PM Maxime Ripard <maxime at cerno.tech> wrote:
> >
> > On Wed, Mar 29, 2023 at 06:46:08PM +0530, Jagan Teki wrote:
> > > Implement a DRM-managed action helper that returns the next DSI bridge
> > > in the chain.
> > >
> > > Unlike general bridge return helper drmm_of_get_bridge, this helper
> > > uses the dsi specific panel_or_bridge helper to find the next DSI
> > > device in the pipeline.
> > >
> > > Helper lookup a given downstream DSI device that has been added via
> > > child or OF-graph port or ports node.
> > >
> > > Upstream DSI looks for downstream devices using drm pointer, port and
> > > endpoint number. Downstream devices added via child node don't affect
> > > the port and endpoint number arguments.
> > >
> > > Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
> >
> > If you intend to use it with the sun4i driver, then don't. The sun4i
> > driver is barely using drm-managed resources, so chances are all its
> > resources will be freed by the time this action will run.
> 
> Any idea how to check all resources will be freed before this
> DRM-managed action helper runs? I did test the panel insertion and
> removal at runtime and I can see that the action helper
> (drmm_drm_panel_bridge_release) is triggered at removal time.
> 
> Here is the log for it.
> # insmod panel-bananapi-s070wv20-icn6211.ko
> [   11.411894] sun4i-drm display-engine: bound
> 1e00000.display-frontend (ops 0xc0951eb4)
> [   11.420253] sun4i-drm display-engine: bound 1e60000.display-backend
> (ops 0xc0951620)
> [   11.428128] sun4i-drm display-engine: bound 1e70000.drc (ops 0xc0951150)
> [   11.435574] sun4i-drm display-engine: No panel or bridge found...
> RGB output disabled
> [   11.443484] sun4i-drm display-engine: bound 1c0c000.lcd-controller
> (ops 0xc094fdb0)
> [   11.451264] sun4i-drm display-engine: bound 1ca0000.dsi (ops 0xc0952f04)
> [   11.462479] [drm] Initialized sun4i-drm 1.0.0 20150629 for
> display-engine on minor 1
> [   11.963246] Console: switching to colour frame buffer device 100x30
> [   12.046329] sun4i-drm display-engine: [drm] fb0: sun4i-drmdrmfb
> frame buffer device
> [   12.082641] sun6i-mipi-dsi 1ca0000.dsi: Attached device s070wv20-ct16-icn62
> # rmmod panel-bananapi-s070wv20-icn6211.ko
> [   16.306388] Console: switching to colour dummy device 80x30
> [   16.466963] drmm_drm_panel_bridge_release: In

Enable KASAN, unload the DSI controller module or unbind its device,
and watch things go boom :)

Maxime
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