This is useful for display parameters. Add a simple decode function to read
from this device tree node.
Signed-off-by: Simon Glass <s...@chromium.org>
---
doc/device-tree-bindings/video/display-timing.txt | 110 ++++++++++++++++++++++
include/fdtdec.h | 80 ++++++++++++++++
lib/fdtdec.c | 92 ++++++++++++++++++
3 files changed, 282 insertions(+)
create mode 100644 doc/device-tree-bindings/video/display-timing.txt
diff --git a/doc/device-tree-bindings/video/display-timing.txt
b/doc/device-tree-bindings/video/display-timing.txt
new file mode 100644
index 0000000..e1d4a0b
--- /dev/null
+++ b/doc/device-tree-bindings/video/display-timing.txt
@@ -0,0 +1,110 @@
+display-timing bindings
+=======================
+
+display-timings node
+--------------------
+
+required properties:
+ - none
+
+optional properties:
+ - native-mode: The native mode for the display, in case multiple modes are
+ provided. When omitted, assume the first node is the native.
+
+timing subnode
+--------------
+
+required properties:
+ - hactive, vactive: display resolution
+ - hfront-porch, hback-porch, hsync-len: horizontal display timing parameters
+ in pixels
+ vfront-porch, vback-porch, vsync-len: vertical display timing parameters in
+ lines
+ - clock-frequency: display clock in Hz
+
+optional properties:
+ - hsync-active: hsync pulse is active low/high/ignored
+ - vsync-active: vsync pulse is active low/high/ignored
+ - de-active: data-enable pulse is active low/high/ignored
+ - pixelclk-active: with
+ - active high = drive pixel data on rising edge/
+ sample data on falling edge
+ - active low = drive pixel data on falling edge/
+ sample data on rising edge
+ - ignored = ignored
+ - interlaced (bool): boolean to enable interlaced mode
+ - doublescan (bool): boolean to enable doublescan mode
+ - doubleclk (bool): boolean to enable doubleclock mode
+
+All the optional properties that are not bool follow the following logic:
+ <1>: high active
+ <0>: low active
+ omitted: not used on hardware
+
+There are different ways of describing the capabilities of a display. The
+devicetree representation corresponds to the one commonly found in datasheets
+for displays. If a display supports multiple signal timings, the native-mode
+can be specified.
+
+The parameters are defined as:
+
+ +----------+-------------------------------------+----------+-------+
+ | | ↑ | | |
+ | | |vback_porch | | |
+ | | ↓ | | |
+ +----------#######################################----------+-------+
+ | # ↑ # | |
+ | # | # | |
+ | hback # | # hfront | hsync |
+ | porch # | hactive # porch | len |
+ |<-------->#<-------+--------------------------->#<-------->|<----->|
+ | # | # | |
+ | # |vactive # | |
+ | # | # | |
+ | # ↓ # | |
+ +----------#######################################----------+-------+
+ | | ↑ | | |
+ | | |vfront_porch | | |
+ | | ↓ | | |
+ +----------+-------------------------------------+----------+-------+
+ | | ↑ | | |
+ | | |vsync_len | | |
+ | | ↓ | | |
+ +----------+-------------------------------------+----------+-------+
+
+Example:
+
+ display-timings {
+ native-mode = <&timing0>;
+ timing0: 1080p24 {
+ /* 1920x1080p24 */
+ clock-frequency = <52000000>;
+ hactive = <1920>;
+ vactive = <1080>;
+ hfront-porch = <25>;
+ hback-porch = <25>;
+ hsync-len = <25>;
+ vback-porch = <2>;
+ vfront-porch = <2>;
+ vsync-len = <2>;
+ hsync-active = <1>;
+ };
+ };
+
+Every required property also supports the use of ranges, so the commonly used
+datasheet description with minimum, typical and maximum values can be used.
+
+Example:
+
+ timing1: timing {
+ /* 1920x1080p24 */
+ clock-frequency = <148500000>;
+ hactive = <1920>;
+ vactive = <1080>;
+ hsync-len = <0 44 60>;
+ hfront-porch = <80 88 95>;
+ hback-porch = <100 148 160>;
+ vfront-porch = <0 4 6>;
+ vback-porch = <0 36 50>;
+ vsync-len = <0 5 6>;
+ };
diff --git a/include/fdtdec.h b/include/fdtdec.h
index b9cdd38..f06e180 100644
--- a/include/fdtdec.h
+++ b/include/fdtdec.h
@@ -728,4 +728,84 @@ int fdtdec_pci_get_bdf(const void *fdt, int node, int
*bdf);
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);
+
+#define BIT(pos) (1U << pos)
+
+/* Display timings from linux include/video/display_timing.h */
+enum display_flags {
+ DISPLAY_FLAGS_HSYNC_LOW = BIT(0),
+ DISPLAY_FLAGS_HSYNC_HIGH = BIT(1),
+ DISPLAY_FLAGS_VSYNC_LOW = BIT(2),
+ DISPLAY_FLAGS_VSYNC_HIGH = BIT(3),
+
+ /* data enable flag */
+ DISPLAY_FLAGS_DE_LOW = BIT(4),
+ DISPLAY_FLAGS_DE_HIGH = BIT(5),
+ /* drive data on pos. edge */
+ DISPLAY_FLAGS_PIXDATA_POSEDGE = BIT(6),
+ /* drive data on neg. edge */
+ DISPLAY_FLAGS_PIXDATA_NEGEDGE = BIT(7),
+ DISPLAY_FLAGS_INTERLACED = BIT(8),
+ DISPLAY_FLAGS_DOUBLESCAN = BIT(9),
+ DISPLAY_FLAGS_DOUBLECLK = BIT(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);
#endif
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index d78712d..3f0b651 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -881,4 +881,96 @@ int fdtdec_decode_memory_region(const void *blob, int
config_node,
return 0;
}
+
+static int decode_timing_property(const void *blob, int node, const char *name,
+ struct timing_entry *result)
+{
+ int length, ret = 0;
+ const u32 *prop;
+
+ prop = fdt_getprop(blob, node, name, &length);
+ if (!prop) {
+ debug("%s: could not find property %s\n",
+ fdt_get_name(blob, node, NULL), name);
+ return length;
+ }
+
+ if (length == sizeof(u32)) {
+ result->typ = fdtdec_get_int(blob, node, name, 0);
+ result->min = result->typ;
+ result->max = result->typ;
+ } else {
+ ret = fdtdec_get_int_array(blob, node, name, &result->min, 3);
+ }
+
+ return ret;
+}
+
+int fdtdec_decode_display_timing(const void *blob, int parent, int index,
+ struct display_timing *dt)
+{
+ int i, node, timings_node;
+ u32 val = 0;
+ int ret = 0;
+
+ timings_node = fdt_subnode_offset(blob, parent, "display-timings");
+ if (timings_node < 0)
+ return timings_node;
+
+ for (i = 0, node = fdt_first_subnode(blob, timings_node);
+ node > 0 && i != index;
+ node = fdt_next_subnode(blob, node))
+ i++;
+
+ if (node < 0)
+ return node;
+
+ memset(dt, 0, sizeof(*dt));
+
+ ret |= decode_timing_property(blob, node, "hback-porch",
+ &dt->hback_porch);
+ ret |= decode_timing_property(blob, node, "hfront-porch",
+ &dt->hfront_porch);
+ ret |= decode_timing_property(blob, node, "hactive", &dt->hactive);
+ ret |= decode_timing_property(blob, node, "hsync-len", &dt->hsync_len);
+ ret |= decode_timing_property(blob, node, "vback-porch",
+ &dt->vback_porch);
+ ret |= decode_timing_property(blob, node, "vfront-porch",
+ &dt->vfront_porch);
+ ret |= decode_timing_property(blob, node, "vactive", &dt->vactive);
+ ret |= decode_timing_property(blob, node, "vsync-len", &dt->vsync_len);
+ ret |= decode_timing_property(blob, node, "clock-frequency",
+ &dt->pixelclock);
+
+ dt->flags = 0;
+ val = fdtdec_get_int(blob, node, "vsync-active", -1);
+ if (val != -1) {
+ dt->flags |= val ? DISPLAY_FLAGS_VSYNC_HIGH :
+ DISPLAY_FLAGS_VSYNC_LOW;
+ }
+ val = fdtdec_get_int(blob, node, "hsync-active", -1);
+ if (val != -1) {
+ dt->flags |= val ? DISPLAY_FLAGS_HSYNC_HIGH :
+ DISPLAY_FLAGS_HSYNC_LOW;
+ }
+ val = fdtdec_get_int(blob, node, "de-active", -1);
+ if (val != -1) {
+ dt->flags |= val ? DISPLAY_FLAGS_DE_HIGH :
+ DISPLAY_FLAGS_DE_LOW;
+ }
+ val = fdtdec_get_int(blob, node, "pixelclk-active", -1);
+ if (val != -1) {
+ dt->flags |= val ? DISPLAY_FLAGS_PIXDATA_POSEDGE :
+ DISPLAY_FLAGS_PIXDATA_NEGEDGE;
+ }
+
+ if (fdtdec_get_bool(blob, node, "interlaced"))
+ dt->flags |= DISPLAY_FLAGS_INTERLACED;
+ if (fdtdec_get_bool(blob, node, "doublescan"))
+ dt->flags |= DISPLAY_FLAGS_DOUBLESCAN;
+ if (fdtdec_get_bool(blob, node, "doubleclk"))
+ dt->flags |= DISPLAY_FLAGS_DOUBLECLK;
+
+ return 0;
+}
#endif
--
2.2.0.rc0.207.ga3a616c
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