From: Fabio Estevam Date: Tue, 20 Jan 2026 23:19:30 +0000 (-0300) Subject: drm/bridge: fsl-ldb: Allow the termination resistor to be enabled X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=a50007089e078a1b7a826559a02277b1601ee189;p=thirdparty%2Flinux.git drm/bridge: fsl-ldb: Allow the termination resistor to be enabled The LVDS Control Register (LVDS_CTRL) register has an HS_EN bit that allows the 100 Ohm termination resistor in the chip to be enabled. Add support to setting the HS_EN bit when the optional property "nxp,enable-termination-resistor" is present. The motivation for introducing this property was a custom i.MX8MP board that was showing visual artifacts. After enabling the 100 Ohm termination resistor the LVDS signal quality improved causing the artifacts to disappear. Signed-off-by: Fabio Estevam Reviewed-by: Liu Ying Signed-off-by: Liu Ying Link: https://lore.kernel.org/r/20260120231930.2782444-2-festevam@gmail.com --- diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fsl-ldb.c index 5c3cf37200bce..7b71cde173e0c 100644 --- a/drivers/gpu/drm/bridge/fsl-ldb.c +++ b/drivers/gpu/drm/bridge/fsl-ldb.c @@ -92,6 +92,7 @@ struct fsl_ldb { const struct fsl_ldb_devdata *devdata; bool ch0_enabled; bool ch1_enabled; + bool use_termination_resistor; }; static bool fsl_ldb_is_dual(const struct fsl_ldb *fsl_ldb) @@ -212,6 +213,9 @@ static void fsl_ldb_atomic_enable(struct drm_bridge *bridge, /* Program LVDS_CTRL */ reg = LVDS_CTRL_CC_ADJ(2) | LVDS_CTRL_PRE_EMPH_EN | LVDS_CTRL_PRE_EMPH_ADJ(3) | LVDS_CTRL_VBG_EN; + + if (fsl_ldb->use_termination_resistor) + reg |= LVDS_CTRL_HS_EN; regmap_write(fsl_ldb->regmap, fsl_ldb->devdata->lvds_ctrl, reg); /* Wait for VBG to stabilize. */ @@ -340,6 +344,9 @@ static int fsl_ldb_probe(struct platform_device *pdev) if (IS_ERR(panel)) return PTR_ERR(panel); + if (of_property_present(dev->of_node, "nxp,enable-termination-resistor")) + fsl_ldb->use_termination_resistor = true; + 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);