On Tue, Jan 10, 2017 at 6:33 AM, Ernst Sjöstrand <ernstp@xxxxxxxxx> wrote: > Isn't 10bpc very common among monitors, and 12bpc very rare? Or maybe I'm > confusing the transport layer with the presentation capabilities...? > Here are 201 monitors that claim 10bpc: > http://pricespy.co.uk/category.php?l=s300859434&o=eg_401#prodlista > FWIW, I've almost never seen a monitor that supports 12 bpc, but I've see quite a few 10 bpc monitors. I can talk to our display team to see what other OSes do. Alex > Regards > //Ernst > > 2017-01-10 11:52 GMT+01:00 Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>: >> >> On Thu, Jan 05, 2017 at 05:45:23PM -0600, Nicholas Sielicki wrote: >> > As per the HDMI 1.3 and 1.4 spec, "deep color modes" are color depths >> > greater than 24 bits per pixel. The spec explicitly states, "All Deep >> > Color modes are optional though if an HDMI Source or Sink supports any >> > Deep Color mode, it shall support 36-bit mode." (6.2.4 Color Depth >> > Requirements). >> > >> > I came across a monitor (Acer X233H) that supplies an illegal EDID where >> > DC_30bit is set and DC_36bit is not set. The end result is badly garbled >> > output because the driver is sending 36BPP when the monitor can't handle >> > it. >> > >> > Much of the intel hardware is incapable of operating at any >> > bit-per-component setting outside of 8 or 12, and the spec seems to >> > imply that if any deep color support is found, then it is a safe >> > assumption to operate at 12. >> > >> > This patch ensures that the EDID is within the spec (specifically, that >> > DC_36bit is set) before committing to going forward with any deep >> > colors. There was already a check for this EDID inconsistency, but it >> > resulted only in a warning and did not fall-back to safer settings. >> > >> > CC: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> > Signed-off-by: Nicholas Sielicki <nicholas.sielicki@xxxxxxxxx> >> > --- >> > drivers/gpu/drm/drm_edid.c | 35 +++++++++++++++++++++++------------ >> > 1 file changed, 23 insertions(+), 12 deletions(-) >> > >> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c >> > index 336be31ff3de..42ce3f54d2dc 100644 >> > --- a/drivers/gpu/drm/drm_edid.c >> > +++ b/drivers/gpu/drm/drm_edid.c >> > @@ -3772,30 +3772,34 @@ static void >> > drm_parse_hdmi_deep_color_info(struct drm_connector *connector, >> > { >> > struct drm_display_info *info = &connector->display_info; >> > unsigned int dc_bpc = 0; >> > + u8 modes = 0; >> > >> > /* HDMI supports at least 8 bpc */ >> > info->bpc = 8; >> > >> > + /* Ensure all DC modes are unset if we return early */ >> > + info->edid_hdmi_dc_modes = 0; >> >> Clearing this in drm_add_display_info() should be sufficient since >> this guy doesn't get called from anywhere else. So this part could >> be droppped. >> >> Otherwise this feels like a decent way to handle the problem. We >> could of course try to use the 10bpc (or whatever) deep color modes >> the sink claims to support, but given that the people designing the >> thing didn't bother reading the spec, it seems safer to just disable >> deep color support entirely. >> >> Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> >> > + >> > if (cea_db_payload_len(hdmi) < 6) >> > return; >> > >> > if (hdmi[6] & DRM_EDID_HDMI_DC_30) { >> > dc_bpc = 10; >> > - info->edid_hdmi_dc_modes |= DRM_EDID_HDMI_DC_30; >> > + modes |= DRM_EDID_HDMI_DC_30; >> > DRM_DEBUG("%s: HDMI sink does deep color 30.\n", >> > connector->name); >> > } >> > >> > if (hdmi[6] & DRM_EDID_HDMI_DC_36) { >> > dc_bpc = 12; >> > - info->edid_hdmi_dc_modes |= DRM_EDID_HDMI_DC_36; >> > + modes |= DRM_EDID_HDMI_DC_36; >> > DRM_DEBUG("%s: HDMI sink does deep color 36.\n", >> > connector->name); >> > } >> > >> > if (hdmi[6] & DRM_EDID_HDMI_DC_48) { >> > dc_bpc = 16; >> > - info->edid_hdmi_dc_modes |= DRM_EDID_HDMI_DC_48; >> > + modes |= DRM_EDID_HDMI_DC_48; >> > DRM_DEBUG("%s: HDMI sink does deep color 48.\n", >> > connector->name); >> > } >> > @@ -3806,9 +3810,24 @@ static void drm_parse_hdmi_deep_color_info(struct >> > drm_connector *connector, >> > return; >> > } >> > >> > + /* >> > + * All deep color modes are optional, but if a sink supports any >> > deep >> > + * color mode, it must support 36-bit mode. If this is found not >> > + * to be the case, sink is in violation of HDMI 1.3 / 1.4 spec and >> > it >> > + * is prudent to disable all deep color modes. Return here before >> > + * committing bpc and edid_hdmi_dc_modes. >> > + */ >> > + if (!(modes & DRM_EDID_HDMI_DC_36)) { >> > + DRM_DEBUG("%s: HDMI sink should do DC_36, but does >> > not!\n", >> > + connector->name); >> > + return; >> > + } >> > + >> > + >> > DRM_DEBUG("%s: Assigning HDMI sink color depth as %d bpc.\n", >> > connector->name, dc_bpc); >> > info->bpc = dc_bpc; >> > + info->edid_hdmi_dc_modes = modes; >> > >> > /* >> > * Deep color support mandates RGB444 support for all video >> > @@ -3823,15 +3842,6 @@ static void drm_parse_hdmi_deep_color_info(struct >> > drm_connector *connector, >> > DRM_DEBUG("%s: HDMI sink does YCRCB444 in deep color.\n", >> > connector->name); >> > } >> > - >> > - /* >> > - * Spec says that if any deep color mode is supported at all, >> > - * then deep color 36 bit must be supported. >> > - */ >> > - if (!(hdmi[6] & DRM_EDID_HDMI_DC_36)) { >> > - DRM_DEBUG("%s: HDMI sink should do DC_36, but does >> > not!\n", >> > - connector->name); >> > - } >> > } >> > >> > static void >> > @@ -3895,6 +3905,7 @@ static void drm_add_display_info(struct >> > drm_connector *connector, >> > /* driver figures it out in this case */ >> > info->bpc = 0; >> > info->color_formats = 0; >> > + info->edid_hdmi_dc_modes = 0; >> > info->cea_rev = 0; >> > info->max_tmds_clock = 0; >> > info->dvi_dual = false; >> > -- >> > 2.11.0 >> >> -- >> Ville Syrjälä >> Intel OTC >> _______________________________________________ >> dri-devel mailing list >> dri-devel@xxxxxxxxxxxxxxxxxxxxx >> https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
