[U-Boot] [PATCH v6 19/26] edid: Add a function to read detailed monitor timings

Simon Glass
2015-04-15T03:03:37Z

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>
---

Changes in v6: None
Changes in v4: None
Changes in v3: None
Changes in v2: None

common/edid.c | 105 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/edid.h | 19 +++++++++++
2 files changed, 124 insertions(+)

diff --git a/common/edid.c b/common/edid.c
index df797fc..e08e420 100644
--- a/common/edid.c
+++ b/common/edid.c
@@ -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.
*
diff --git a/include/edid.h b/include/edid.h
index 18ec1d5..88b4b7d 100644
--- a/include/edid.h
+++ b/include/edid.h
@@ -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_ */
--
2.2.0.rc0.207.ga3a616c