drm/imx: imx-ldb: disable LDB on driver bind

[ Upstream commit b58262396fabd43dc869b576e3defdd23b32fe94 ]

The LVDS signal integrity is only guaranteed when the correct enable
sequence (first IPU DI, then LDB) is used. If the LDB display output was
active before the imx-drm driver is loaded (like when a bootsplash was
active) the DI will be disabled by the full IPU reset we do when loading
the driver. The LDB control registers are not part of the IPU range and
thus will remain unchanged.

This leads to the LDB still being active when the DI is getting enabled,
effectively reversing the required enable sequence. Fix this by also
disabling the LDB on driver bind.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
index 3ce391c239b02ace097ab4fbfb89deaaebb24618..7c563b5f068360851cf2fe22e6c8cff1b8eb0ef4 100644 (file)
--- a/drivers/gpu/drm/imx/imx-ldb.c
+++ b/drivers/gpu/drm/imx/imx-ldb.c
@@ -634,6 +634,9 @@ static int imx_ldb_bind(struct device *dev, struct device *master, void *data)
                return PTR_ERR(imx_ldb->regmap);
        }
 
+       /* disable LDB by resetting the control register to POR default */
+       regmap_write(imx_ldb->regmap, IOMUXC_GPR2, 0);
+
        imx_ldb->dev = dev;
 
        if (of_id)