phy: phy-mtk-dp: Fix an error code in probe()

Negative -EINVAL was intended instead of positive EINVAL.

Fixes: 6a23afad443a ("phy: phy-mtk-dp: Add driver for DP phy")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/3c699e00-2883-40d9-92c3-0da1dc38fdd4@moroto.mountain
Signed-off-by: Vinod Koul <vkoul@kernel.org>

phy: phy-mtk-dp: make array driving_params static const

Don't populate the read-only array driving_params on the stack but instead
make it static const. Also makes the object code a little smaller.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220929130147.97375-1-colin.i.king@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

phy: phy-mtk-dp: change mtk_dp_phy_driver to static

mtk_dp_phy_driver is only used in phy-mtk-dp.c now, change it to static.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220707135309.801181-1-yangyingliang@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

phy: phy-mtk-dp: Add driver for DP phy

This is a new driver that supports the integrated DisplayPort phy for
mediatek SoCs, especially the mt8195. The phy is integrated into the
DisplayPort controller and will be created by the mtk-dp driver. This
driver expects a struct regmap to be able to work on the same registers
as the DisplayPort controller. It sets the device data to be the struct
phy so that the DisplayPort controller can easily work with it.

The driver does not have any devicetree bindings because the datasheet
does not list the controller and the phy as distinct units.

The interaction with the controller can be covered by the configure
callback of the phy framework and its displayport parameters.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
[Bo-Chen: Modify reviewers' comments.]
Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220624062725.4095-1-rex-bc.chen@mediatek.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>