edid: Add a function to read detailed monitor timings

For digital displays (such as EDP LCDs) we would like to read the EDID
information and use that to set display timings. Provide a function to do
this.

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 21:03:37 -06:00 committed by Tom Warren
parent 490f5fd238
commit 00cf1167bb
2 changed files with 124 additions and 0 deletions

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@ -13,6 +13,7 @@
#include <common.h>
#include <edid.h>
#include <errno.h>
#include <fdtdec.h>
#include <linux/ctype.h>
#include <linux/string.h>
@ -65,6 +66,110 @@ int edid_get_ranges(struct edid1_info *edid, unsigned int *hmin,
return -1;
}
/* Set all parts of a timing entry to the same value */
static void set_entry(struct timing_entry *entry, u32 value)
{
entry->min = value;
entry->typ = value;
entry->max = value;
}
/**
* decode_timing() - Decoding an 18-byte detailed timing record
*
* @buf: Pointer to EDID detailed timing record
* @timing: Place to put timing
*/
static void decode_timing(u8 *buf, struct display_timing *timing)
{
uint x_mm, y_mm;
unsigned int ha, hbl, hso, hspw, hborder;
unsigned int va, vbl, vso, vspw, vborder;
/* Edid contains pixel clock in terms of 10KHz */
set_entry(&timing->pixelclock, (buf[0] + (buf[1] << 8)) * 10000);
x_mm = (buf[12] + ((buf[14] & 0xf0) << 4));
y_mm = (buf[13] + ((buf[14] & 0x0f) << 8));
ha = (buf[2] + ((buf[4] & 0xf0) << 4));
hbl = (buf[3] + ((buf[4] & 0x0f) << 8));
hso = (buf[8] + ((buf[11] & 0xc0) << 2));
hspw = (buf[9] + ((buf[11] & 0x30) << 4));
hborder = buf[15];
va = (buf[5] + ((buf[7] & 0xf0) << 4));
vbl = (buf[6] + ((buf[7] & 0x0f) << 8));
vso = ((buf[10] >> 4) + ((buf[11] & 0x0c) << 2));
vspw = ((buf[10] & 0x0f) + ((buf[11] & 0x03) << 4));
vborder = buf[16];
set_entry(&timing->hactive, ha);
set_entry(&timing->hfront_porch, hso);
set_entry(&timing->hback_porch, hbl - hso - hspw);
set_entry(&timing->hsync_len, hspw);
set_entry(&timing->vactive, va);
set_entry(&timing->vfront_porch, vso);
set_entry(&timing->vback_porch, vbl - vso - vspw);
set_entry(&timing->vsync_len, vspw);
debug("Detailed mode clock %u Hz, %d mm x %d mm\n"
" %04x %04x %04x %04x hborder %x\n"
" %04x %04x %04x %04x vborder %x\n",
timing->pixelclock.typ,
x_mm, y_mm,
ha, ha + hso, ha + hso + hspw,
ha + hbl, hborder,
va, va + vso, va + vso + vspw,
va + vbl, vborder);
}
int edid_get_timing(u8 *buf, int buf_size, struct display_timing *timing,
int *panel_bits_per_colourp)
{
struct edid1_info *edid = (struct edid1_info *)buf;
bool timing_done;
int i;
if (buf_size < sizeof(*edid) || edid_check_info(edid)) {
debug("%s: Invalid buffer\n", __func__);
return -EINVAL;
}
if (!EDID1_INFO_FEATURE_PREFERRED_TIMING_MODE(*edid)) {
debug("%s: No preferred timing\n", __func__);
return -ENOENT;
}
/* Look for detailed timing */
timing_done = false;
for (i = 0; i < 4; i++) {
struct edid_monitor_descriptor *desc;
desc = &edid->monitor_details.descriptor[i];
if (desc->zero_flag_1 != 0) {
decode_timing((u8 *)desc, timing);
timing_done = true;
break;
}
}
if (!timing_done)
return -EINVAL;
if (!EDID1_INFO_VIDEO_INPUT_DIGITAL(*edid)) {
debug("%s: Not a digital display\n", __func__);
return -ENOSYS;
}
if (edid->version != 1 || edid->revision < 4) {
debug("%s: EDID version %d.%d does not have required info\n",
__func__, edid->version, edid->revision);
*panel_bits_per_colourp = -1;
} else {
*panel_bits_per_colourp =
((edid->video_input_definition & 0x70) >> 3) + 4;
}
return 0;
}
/**
* Snip the tailing whitespace/return of a string.
*

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@ -15,6 +15,9 @@
#include <linux/types.h>
/* Size of the EDID data */
#define EDID_SIZE 128
#define GET_BIT(_x, _pos) \
(((_x) >> (_pos)) & 1)
#define GET_BITS(_x, _pos_msb, _pos_lsb) \
@ -287,4 +290,20 @@ int edid_get_ranges(struct edid1_info *edid, unsigned int *hmin,
unsigned int *hmax, unsigned int *vmin,
unsigned int *vmax);
struct display_timing;
/**
* edid_get_timing() - Get basic digital display parameters
*
* @param buf Buffer containing EDID data
* @param buf_size Size of buffer in bytes
* @param timing Place to put preferring timing information
* @param panel_bits_per_colourp Place to put the number of bits per
* colour supported by the panel. This will be set to
* -1 if not available
* @return 0 if timings are OK, -ve on error
*/
int edid_get_timing(u8 *buf, int buf_size, struct display_timing *timing,
int *panel_bits_per_colourp);
#endif /* __EDID_H_ */