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_ */