On Thu, Dec 14, 2023 at 03:10:43PM +0000, Dave Stevenson wrote:
> > +static bool
> > +sink_supports_format_bpc(const struct drm_connector *connector,
> > + const struct drm_display_info *info,
> > + const struct drm_display_mode *mode,
> > + unsigned int format, unsigned int bpc)
> > +{
> > + struct drm_device *dev = connector->dev;
> > + u8 vic = drm_match_cea_mode(mode);
> > +
> > + if (vic == 1 && bpc != 8) {
> > + drm_dbg(dev, "VIC1 requires a bpc of 8, got %u\n", bpc);
> > + return false;
> > + }
> > +
> > + if (!info->is_hdmi &&
> > + (format != HDMI_COLORSPACE_RGB || bpc != 8)) {
> > + drm_dbg(dev, "DVI Monitors require an RGB output at 8 bpc\n");
> > + return false;
> > + }
> > +
> > + if (!(connector->hdmi.supported_formats & BIT(format))) {
> > + drm_dbg(dev, "%s format unsupported by the connector.\n",
> > + drm_hdmi_connector_get_output_format_name(format));
> > + return false;
> > + }
> > +
> > + switch (format) {
> > + case HDMI_COLORSPACE_RGB:
> > + drm_dbg(dev, "RGB Format, checking the constraints.\n");
> > +
> > + if (!(info->color_formats & DRM_COLOR_FORMAT_RGB444))
> > + return false;
>
> We've dropped this check from vc4 in our downstream kernel as it stops
> you using the prebaked EDIDs (eg drm.edid_firmware=edid/1024x768.bin),
> or any other EDID that is defined as an analog monitor.
> The EDID parsing bombs out at [1], so info->color_formats gets left at 0.
Right, but it only does so if the display isn't defined as a digital display...
> RGB is mandatory for both DVI and HDMI, so rejecting it seems overly fussy.
... which is required for both DVI and HDMI.
And sure enough, if we decode that EDID:
edid-decode (hex):
00 ff ff ff ff ff ff 00 31 d8 00 00 00 00 00 00
05 16 01 03 6d 23 1a 78 ea 5e c0 a4 59 4a 98 25
20 50 54 00 08 00 61 40 01 01 01 01 01 01 01 01
01 01 01 01 01 01 64 19 00 40 41 00 26 30 08 90
36 00 63 0a 11 00 00 18 00 00 00 ff 00 4c 69 6e
75 78 20 23 30 0a 20 20 20 20 00 00 00 fd 00 3b
3d 2f 31 07 00 0a 20 20 20 20 20 20 00 00 00 fc
00 4c 69 6e 75 78 20 58 47 41 0a 20 20 20 00 55
----------------
Block 0, Base EDID:
EDID Structure Version & Revision: 1.3
Vendor & Product Identification:
Manufacturer: LNX
Model: 0
Made in: week 5 of 2012
Basic Display Parameters & Features:
Analog display
Signal Level Standard: 0.700 : 0.000 : 0.700 V p-p
Blank level equals black level
Sync: Separate Composite Serration
Maximum image size: 35 cm x 26 cm
Gamma: 2.20
DPMS levels: Standby Suspend Off
RGB color display
First detailed timing is the preferred timing
Color Characteristics:
Red : 0.6416, 0.3486
Green: 0.2919, 0.5957
Blue : 0.1474, 0.1250
White: 0.3125, 0.3281
Established Timings I & II:
DMT 0x10: 1024x768 60.003840 Hz 4:3 48.363 kHz 65.000000 MHz
Standard Timings:
DMT 0x10: 1024x768 60.003840 Hz 4:3 48.363 kHz 65.000000 MHz
Detailed Timing Descriptors:
DTD 1: 1024x768 60.003840 Hz 4:3 48.363 kHz 65.000000 MHz (355 mm x 266 mm)
Hfront 8 Hsync 144 Hback 168 Hpol N
Vfront 3 Vsync 6 Vback 29 Vpol N
Display Product Serial Number: 'Linux #0'
Display Range Limits:
Monitor ranges (GTF): 59-61 Hz V, 47-49 kHz H, max dotclock 70 MHz
Display Product Name: 'Linux XGA'
Checksum: 0x55
----------------
Warnings:
Block 0, Base EDID:
Detailed Timing Descriptor #1: DTD is similar but not identical to DMT 0x10.
EDID conformity: PASS
So, if anything, it's the EDID that needs to be updated, not the code there.
Maxime
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