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fdt: Add binding decode function for display-timings

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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>
This commit is contained in:
Simon Glass 2015-04-14 21:03:21 -06:00 committed by Tom Warren
parent 962f5caf60
commit 12e671142d
3 changed files with 279 additions and 0 deletions
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110
doc/device-tree-bindings/video/display-timing.txt Normal file
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@ -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>;
};

77
include/fdtdec.h
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@ -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
*/

92
lib/fdtdec.c
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@ -1037,6 +1037,98 @@ 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;
}
int fdtdec_setup(void)
{
#ifdef CONFIG_OF_CONTROL