fdt: Add binding decode function for display-timings

This is useful for display parameters. Add a simple decode function to read
from this device tree node.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/include/fdtdec.h b/include/fdtdec.h
index f11475b5fd..f304199e1d 100644
--- a/include/fdtdec.h
+++ b/include/fdtdec.h
@@ -802,6 +802,83 @@ int fdtdec_decode_memory_region(const void *blob, int node,
 				const char *mem_type, const char *suffix,
 				fdt_addr_t *basep, fdt_size_t *sizep);
 
+/* Display timings from linux include/video/display_timing.h */
+enum display_flags {
+	DISPLAY_FLAGS_HSYNC_LOW		= 1 << 0,
+	DISPLAY_FLAGS_HSYNC_HIGH	= 1 << 1,
+	DISPLAY_FLAGS_VSYNC_LOW		= 1 << 2,
+	DISPLAY_FLAGS_VSYNC_HIGH	= 1 << 3,
+
+	/* data enable flag */
+	DISPLAY_FLAGS_DE_LOW		= 1 << 4,
+	DISPLAY_FLAGS_DE_HIGH		= 1 << 5,
+	/* drive data on pos. edge */
+	DISPLAY_FLAGS_PIXDATA_POSEDGE	= 1 << 6,
+	/* drive data on neg. edge */
+	DISPLAY_FLAGS_PIXDATA_NEGEDGE	= 1 << 7,
+	DISPLAY_FLAGS_INTERLACED	= 1 << 8,
+	DISPLAY_FLAGS_DOUBLESCAN	= 1 << 9,
+	DISPLAY_FLAGS_DOUBLECLK		= 1 << 10,
+};
+
+/*
+ * A single signal can be specified via a range of minimal and maximal values
+ * with a typical value, that lies somewhere inbetween.
+ */
+struct timing_entry {
+	u32 min;
+	u32 typ;
+	u32 max;
+};
+
+/*
+ * Single "mode" entry. This describes one set of signal timings a display can
+ * have in one setting. This struct can later be converted to struct videomode
+ * (see include/video/videomode.h). As each timing_entry can be defined as a
+ * range, one struct display_timing may become multiple struct videomodes.
+ *
+ * Example: hsync active high, vsync active low
+ *
+ *				    Active Video
+ * Video  ______________________XXXXXXXXXXXXXXXXXXXXXX_____________________
+ *	  |<- sync ->|<- back ->|<----- active ----->|<- front ->|<- sync..
+ *	  |	     |	 porch  |		     |	 porch	 |
+ *
+ * HSync _|¯¯¯¯¯¯¯¯¯¯|___________________________________________|¯¯¯¯¯¯¯¯¯
+ *
+ * VSync ¯|__________|¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯|_________
+ */
+struct display_timing {
+	struct timing_entry pixelclock;
+
+	struct timing_entry hactive;		/* hor. active video */
+	struct timing_entry hfront_porch;	/* hor. front porch */
+	struct timing_entry hback_porch;	/* hor. back porch */
+	struct timing_entry hsync_len;		/* hor. sync len */
+
+	struct timing_entry vactive;		/* ver. active video */
+	struct timing_entry vfront_porch;	/* ver. front porch */
+	struct timing_entry vback_porch;	/* ver. back porch */
+	struct timing_entry vsync_len;		/* ver. sync len */
+
+	enum display_flags flags;		/* display flags */
+};
+
+/**
+ * fdtdec_decode_display_timing() - decode display timings
+ *
+ * Decode display timings from the supplied 'display-timings' node.
+ * See doc/device-tree-bindings/video/display-timing.txt for binding
+ * information.
+ *
+ * @param blob		FDT blob
+ * @param node		'display-timing' node containing the timing subnodes
+ * @param index		Index number to read (0=first timing subnode)
+ * @param config	Place to put timings
+ * @return 0 if OK, -FDT_ERR_NOTFOUND if not found
+ */
+int fdtdec_decode_display_timing(const void *blob, int node, int index,
+				 struct display_timing *config);
 /**
  * Set up the device tree ready for use
  */