drm/fsl-dcu: add extra clock for pixel clock

The Vybrid DCU variant has two independent clock inputs, one
for the registers (IPG bus clock) and one for the pixel clock.
Support this distinction in the DCU DRM driver while staying
backward compatible for old device trees.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stefan Agner <stefan@agner.ch>

Documentation/devicetree/bindings/display/fsl,dcu.txt

@@ -6,8 +6,11 @@ Required properties:
 	* "fsl,vf610-dcu".
 
 - reg:			Address and length of the register set for dcu.
-- clocks:		From common clock binding: handle to dcu clock.
-- clock-names:		From common clock binding: Shall be "dcu".
+- clocks:		Handle to "dcu" and "pix" clock (in the order below)
+			This can be the same clock (e.g. LS1021a)
+			See ../clocks/clock-bindings.txt for details.
+- clock-names:		Should be "dcu" and "pix"
+			See ../clocks/clock-bindings.txt for details.
 - big-endian		Boolean property, LS1021A DCU registers are big-endian.
 - fsl,panel:		The phandle to panel node.
 
@@ -15,8 +18,8 @@ Examples:
 dcu: dcu@2ce0000 {
 	compatible = "fsl,ls1021a-dcu";
 	reg = <0x0 0x2ce0000 0x0 0x10000>;
-	clocks = <&platform_clk 0>;
-	clock-names = "dcu";
+	clocks = <&platform_clk 0>, <&platform_clk 0>;
+	clock-names = "dcu", "pix";
 	big-endian;
 	fsl,panel = <&panel>;
 };

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_crtc.c

@@ -71,7 +71,7 @@ static void fsl_dcu_drm_crtc_mode_set_nofb(struct drm_crtc *crtc)
 	unsigned long dcuclk;
 
 	index = drm_crtc_index(crtc);
-	dcuclk = clk_get_rate(fsl_dev->clk);
+	dcuclk = clk_get_rate(fsl_dev->pix_clk);
 	div = dcuclk / mode->clock / 1000;
 
 	/* Configure timings: */

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c

@@ -331,10 +331,21 @@ static int fsl_dcu_drm_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	fsl_dev->pix_clk = devm_clk_get(dev, "pix");
+	if (IS_ERR(fsl_dev->pix_clk)) {
+		/* legancy binding, use dcu clock as pixel clock */
+		fsl_dev->pix_clk = fsl_dev->clk;
+	}
+	ret = clk_prepare_enable(fsl_dev->pix_clk);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable pix clk\n");
+		goto disable_clk;
+	}
+
 	drm = drm_dev_alloc(driver, dev);
 	if (!drm) {
 		ret = -ENOMEM;
-		goto disable_clk;
+		goto disable_pix_clk;
 	}
 
 	fsl_dev->dev = dev;
@@ -355,6 +366,8 @@ static int fsl_dcu_drm_probe(struct platform_device *pdev)
 
 unref:
 	drm_dev_unref(drm);
+disable_pix_clk:
+	clk_disable_unprepare(fsl_dev->pix_clk);
 disable_clk:
 	clk_disable_unprepare(fsl_dev->clk);
 	return ret;
@@ -365,6 +378,7 @@ static int fsl_dcu_drm_remove(struct platform_device *pdev)
 	struct fsl_dcu_drm_device *fsl_dev = platform_get_drvdata(pdev);
 
 	clk_disable_unprepare(fsl_dev->clk);
+	clk_disable_unprepare(fsl_dev->pix_clk);
 	drm_put_dev(fsl_dev->drm);
 
 	return 0;

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h

@@ -183,6 +183,7 @@ struct fsl_dcu_drm_device {
 	struct regmap *regmap;
 	int irq;
 	struct clk *clk;
+	struct clk *pix_clk;
 	/*protects hardware register*/
 	spinlock_t irq_lock;
 	struct drm_device *drm;