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Tue, 28 Oct 2025 13:27:37 +0100 (CET) From: Alexander Stein To: Liu Ying , Marek Vasut , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Francesco Valla Cc: Fabian Pflug , dri-devel@lists.freedesktop.org, imx@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/bridge: ldb: add support for an external bridge Date: Tue, 28 Oct 2025 13:27:37 +0100 Message-ID: <1944228.tdWV9SEqCh@steina-w> Organization: TQ-Systems GmbH In-Reply-To: <20251028-imx93_ldb_bridge-v1-1-fca2e7d60e0a@valla.it> References: <20251028-imx93_ldb_bridge-v1-1-fca2e7d60e0a@valla.it> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" X-cloud-security-sender:alexander.stein@ew.tq-group.com X-cloud-security-recipient:linux-kernel@vger.kernel.org X-cloud-security-crypt: load encryption module X-cloud-security-Mailarchiv: E-Mail archived for: alexander.stein@ew.tq-group.com X-cloud-security-Mailarchivtype:outbound X-cloud-security-Virusscan:CLEAN X-cloud-security-disclaimer: This E-Mail was scanned by E-Mailservice on mx-relay12-hz2.antispameurope.com with 4cwqQL3mttz3BKkc X-cloud-security-connect: he-nlb01-hz1.hornetsecurity.com[94.100.132.6], TLS=1, IP=94.100.132.6 X-cloud-security-Digest:672ff784a508aef985d73529930087ab X-cloud-security:scantime:1.873 DKIM-Signature: a=rsa-sha256; bh=968rqhHVFcxnYfiQeYIAS+1AueuObuJtnvbjiS2I6xI=; c=relaxed/relaxed; d=ew.tq-group.com; h=content-type:mime-version:subject:from:to:message-id:date; s=hse1; t=1761654473; v=1; b=a7lPdUt4cNW17lqhZ7RPFzxAniBZWYARrXJ2NERb/hTgfHpEZvrkOEKScfkO0jGzRCYU/9RZ cyLYsbAV6sK+1qdgPVhnk+0LaEN8AN3uY+acvEBcVkyfV65cFpD8WWpDqIfQ6IlFrSRJer18sGO NjcBA3hfapHcmH8NFIE47U6ZS+LA14c2ijUpT8uf8f4MYCGK2R2OQnaRr2TbcZlqyJXd8empxrQ NcPVzOKzAlkq0S4ypPpLYPZKQsCnkGmPW4yyULBp7XhC2BNHejlXxjDODnvmQHlXwkRdnnTPqiH 8QZF9TcECB7rvy3tiWBTtjN6TUNKt3i2AbzlAsNIVJyvA== 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. >=20 > Signed-off-by: Francesco Valla > --- > 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. >=20 > 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. >=20 > 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. >=20 > [1] https://lore.kernel.org/all/20251022-fpg-nxp-imx93-frdm-v3-1-03ec40a1= ccc0@pengutronix.de > [2] https://lore.kernel.org/all/20250304154929.1785200-1-alexander.stein@= ew.tq-group.com > [3] https://elixir.bootlin.com/linux/v6.17.5/source/arch/arm64/boot/dts/f= reescale/imx8mp-evk-lvds0-imx-dlvds-hdmi-channel0.dtso >=20 > Regards, > Francesco > --- > drivers/gpu/drm/bridge/fsl-ldb.c | 26 +++++++++++++++++--------- > 1 file changed, 17 insertions(+), 9 deletions(-) >=20 > diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fs= l-ldb.c > index 5c3cf37200bcee1db285c97e2b463c9355ee6acb..fad436f2e0bfac8b42096a6fc= d0022da0f35284e 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 =3D &pdev->dev; > struct device_node *panel_node; > struct device_node *remote1, *remote2; > - struct drm_panel *panel; > struct fsl_ldb *fsl_ldb; > int dual_link; > =20 > @@ -335,15 +334,24 @@ static int fsl_ldb_probe(struct platform_device *pd= ev) > fsl_ldb_is_dual(fsl_ldb) ? "dual-link mode" : > fsl_ldb->ch0_enabled ? "channel 0" : "channel 1"); > =20 > - panel =3D of_drm_find_panel(panel_node); > - of_node_put(panel_node); > - if (IS_ERR(panel)) > - return PTR_ERR(panel); > - > - fsl_ldb->panel_bridge =3D 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 =3D of_drm_find_bridge(panel_node); > + if (fsl_ldb->panel_bridge) { > + of_node_put(panel_node); > + } else { > + struct drm_panel *panel; > =20 > + panel =3D 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 =3D 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 varian= t. Best regards, Alexander > =20 > if (fsl_ldb_is_dual(fsl_ldb)) { > struct device_node *port1, *port2; >=20 > --- > base-commit: fd57572253bc356330dbe5b233c2e1d8426c66fd > change-id: 20251028-imx93_ldb_bridge-3c011e7856dc >=20 > Best regards, >=20 =2D-=20 TQ-Systems GmbH | M=FChlstra=DFe 2, Gut Delling | 82229 Seefeld, Germany Amtsgericht M=FCnchen, HRB 105018 Gesch=E4ftsf=FChrer: Detlef Schneider, R=FCdiger Stahl, Stefan Schneider http://www.tq-group.com/