drm/rockchip: dsi: add own additional pclk handling

In a followup patch, we'll need to access the pclk ourself to enable some
functionality, so get and store it in the rockchip dw-dsi variant as well.

Clocks are refcounted, so possible cascading enablements are
no problem.
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Tested-by: Sebastian Fricke <sebastian.fricke@posteo.net>
Acked-by: Helen Koike <helen.koike@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210210111020.2476369-2-heiko@sntech.de

drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c

@@ -223,6 +223,7 @@ struct dw_mipi_dsi_rockchip {
 	void __iomem *base;
 
 	struct regmap *grf_regmap;
+	struct clk *pclk;
 	struct clk *pllref_clk;
 	struct clk *grf_clk;
 	struct clk *phy_cfg_clk;
@@ -1065,6 +1066,13 @@ static int dw_mipi_dsi_rockchip_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	dsi->pclk = devm_clk_get(dev, "pclk");
+	if (IS_ERR(dsi->pclk)) {
+		ret = PTR_ERR(dsi->pclk);
+		DRM_DEV_ERROR(dev, "Unable to get pclk: %d\n", ret);
+		return ret;
+	}
+
 	dsi->pllref_clk = devm_clk_get(dev, "ref");
 	if (IS_ERR(dsi->pllref_clk)) {
 		if (dsi->phy) {