Hi Francesco,
Am Dienstag, 28. Oktober 2025, 13:12:29 CET schrieb Francesco Valla:
> One option for the LVDS port of the LDB is to be connected to an
> additional bridge, such as a LVDS to HDMI converter. Add support for
> such case, along with the direct connection to a panel.
>
> Signed-off-by: Francesco Valla <[email protected]>
> ---
> I was trying to add display support for the i.MX93 FRDM on top of the
> patch sent some time ago by Fabian Pflug [1], using some of the work
> already done by Alexander Stein but not yet merged [2], but then I
> noticed that the support for LVDS-HDMI converter bridges was missing
> from the LDB driver already present for the i.MX93.
>
> Not a fail of the driver itself, obviously, but I wonder if/how the
> existing i.MX8MP setups (e.g.: [3]), which use the same driver, work
> correclty. Unfortunately I don't have the i.MX8MP hardware to test them.
>
> Anyhow, a patch for such setup is attached; it was tested on the i.MX93
> FRDM using [1] and [2] plus some more devicetree modifications.
>
> [1]
> https://lore.kernel.org/all/[email protected]
> [2]
> https://lore.kernel.org/all/[email protected]
> [3]
> https://elixir.bootlin.com/linux/v6.17.5/source/arch/arm64/boot/dts/freescale/imx8mp-evk-lvds0-imx-dlvds-hdmi-channel0.dtso
>
> Regards,
> Francesco
> ---
> drivers/gpu/drm/bridge/fsl-ldb.c | 26 +++++++++++++++++---------
> 1 file changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c
> b/drivers/gpu/drm/bridge/fsl-ldb.c
> index
> 5c3cf37200bcee1db285c97e2b463c9355ee6acb..fad436f2e0bfac8b42096a6fcd0022da0f35284e
> 100644
> --- a/drivers/gpu/drm/bridge/fsl-ldb.c
> +++ b/drivers/gpu/drm/bridge/fsl-ldb.c
> @@ -294,7 +294,6 @@ static int fsl_ldb_probe(struct platform_device *pdev)
> struct device *dev = &pdev->dev;
> struct device_node *panel_node;
> struct device_node *remote1, *remote2;
> - struct drm_panel *panel;
> struct fsl_ldb *fsl_ldb;
> int dual_link;
>
> @@ -335,15 +334,24 @@ static int fsl_ldb_probe(struct platform_device *pdev)
> fsl_ldb_is_dual(fsl_ldb) ? "dual-link mode" :
> fsl_ldb->ch0_enabled ? "channel 0" : "channel 1");
>
> - panel = of_drm_find_panel(panel_node);
> - of_node_put(panel_node);
> - if (IS_ERR(panel))
> - return PTR_ERR(panel);
> -
> - fsl_ldb->panel_bridge = devm_drm_panel_bridge_add(dev, panel);
> - if (IS_ERR(fsl_ldb->panel_bridge))
> - return PTR_ERR(fsl_ldb->panel_bridge);
> + /* First try to get an additional bridge, if not found go for a panel */
> + fsl_ldb->panel_bridge = of_drm_find_bridge(panel_node);
> + if (fsl_ldb->panel_bridge) {
> + of_node_put(panel_node);
> + } else {
> + struct drm_panel *panel;
>
> + panel = of_drm_find_panel(panel_node);
> + of_node_put(panel_node);
> + if (IS_ERR(panel))
> + return dev_err_probe(dev, PTR_ERR(panel),
> + "Failed to find panel");
> +
> + fsl_ldb->panel_bridge = devm_drm_panel_bridge_add(dev, panel);
> + if (IS_ERR(fsl_ldb->panel_bridge))
> + return dev_err_probe(dev,
> PTR_ERR(fsl_ldb->panel_bridge),
> + "Failed to add panel bridge");
> + }
Without looking into the details this somehow looks similar to
drm_of_find_panel_or_bridge(), or drmm_of_get_bridge for the managed variant.
Best regards,
Alexander
>
> if (fsl_ldb_is_dual(fsl_ldb)) {
> struct device_node *port1, *port2;
>
> ---
> base-commit: fd57572253bc356330dbe5b233c2e1d8426c66fd
> change-id: 20251028-imx93_ldb_bridge-3c011e7856dc
>
> Best regards,
>
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