drm/armada: add and use definitions for RDREG4F

Add and use bit definitions for RDREG4F on Dove Armada 510.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

drivers/gpu/drm/armada/armada_510.c

@@ -24,8 +24,13 @@ static int armada510_crtc_init(struct armada_crtc *dcrtc, struct device *dev)
 
 	dcrtc->extclk[0] = clk;
 
-	/* Lower the watermark so to eliminate jitter at higher bandwidths */
-	armada_updatel(0x20, (1 << 11) | 0xff, dcrtc->base + LCD_CFG_RDREG4F);
+	/*
+	 * Lower the watermark so to eliminate jitter at higher bandwidths.
+	 * Disable SRAM read wait state to avoid system hang with external
+	 * clock.
+	 */
+	armada_updatel(CFG_DMA_WM(0x20), CFG_SRAM_WAIT | CFG_DMA_WM_MASK,
+		       dcrtc->base + LCD_CFG_RDREG4F);
 
 	/* Initialise SPU register */
 	writel_relaxed(ADV_HWC32ENABLE | ADV_HWC32ARGB | ADV_HWC32BLEND,

drivers/gpu/drm/armada/armada_hw.h

@@ -88,6 +88,16 @@ enum {
 	ADV_VSYNC_H_OFF	= 0xfff << 0,
 };
 
+/* LCD_CFG_RDREG4F - Armada 510 only */
+enum {
+	CFG_SRAM_WAIT	= BIT(11),
+	CFG_SMPN_FASTTX	= BIT(10),
+	CFG_DMA_ARB	= BIT(9),
+	CFG_DMA_WM_EN	= BIT(8),
+	CFG_DMA_WM_MASK	= 0xff,
+#define CFG_DMA_WM(x)	((x) & CFG_DMA_WM_MASK)
+};
+
 enum {
 	CFG_565		= 0,
 	CFG_1555	= 1,