[Bug 110496] [GLK] no signal - with samsung 4k TV - HDMI UHD Color (ENABLED)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110496

--- Comment #30 from shashank.sharma at intel.com <shashank.sharma at intel.com> ---
(In reply to sergey79 from comment #29)
> (In reply to shashank.sharma at intel.com from comment #27)
> 
> > That's why we can see 4k at 30 deep color, 4k at 60 YCBCR 420 deep color outputs
> > working on this TV, but as soon as we switch to RGB 4k at 60, the driver
> > restricts the HDMI output to 4k at 60 8BPC, which is being rejected by the TV,
> > in the UHD mode of operation.
> 
> 420 works only @50/60Hz, only @ 8-bit. 420 @ deep color and other refresh
> rates (24/25/30) is not supported by the TV at all (with UHD Color on or
> off).
4K 420 is targeted for 50/60Hz only.
> 
> The only difference between "HDMI UHD Color" on and off is that TV sends
> different EDID data. I analyzed both EDIDs - basically the only important
> difference is the presence of HDMI-Forum VSDB block which enable Deep Color
> in 4k modes. 
> 
The presence of HF_VSDB indicates HDMI 2.0 EDID, not deep color. Deep color can
be supported in HDMI 1.4b EDIDs too if the clock supports. 

> 4k modes that work (UHD Color off):
> RGB 24/25/30Hz 8-bit
> 420 50/60Hz 8-bit
> 
> 4k modes that don't work (UHD Color on):
> RGB 24/25/30Hz 12-bit
> RGB 50/60Hz 8-bit

Can you also dump 420VDB and 420CMDB from the CEA-extension blocks?  


> 
> As you can see, any mode that require 594 Mhz pixel clock - does not work.
> And any mode that require only 297 Mhz - works just fine.

GLK supports 4k at 60 RGB at 597Mhz well, as we have tested it with several other TVs
and monitors. We are seeing this behavior on this TV only, and that's why I
suspected if it's expecting something different. The UHD/Deep color mode is of
operation is not clear to me yet.   

- Shashank

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