On 05/30/2017 09:49 AM, Hans Verkuil wrote:
On 05/30/2017 04:19 PM, Clint Taylor wrote:
On 05/30/2017 12:11 AM, Jani Nikula wrote:
On Tue, 30 May 2017, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
On 05/29/2017 09:00 PM, Daniel Vetter wrote:
On Fri, May 26, 2017 at 12:20:48PM +0200, Hans Verkuil wrote:
On 05/26/2017 09:15 AM, Daniel Vetter wrote:
Did you look into also wiring this up for dp mst chains?
Isn't this sufficient? I have no way of testing mst chains.
I think I need some pointers from you, since I am a complete
newbie when it
comes to mst.
I don't really have more clue, but yeah if you don't have an mst
thing (a
simple dp port multiplexer is what I use for testing here, then
plug in a
converter dongle or cable into that) then probably better to not
wire up
the code for it.
I think my NUC already uses mst internally. But I was planning on
buying a
dp multiplexer to make sure there is nothing special I need to do
for mst.
The CEC Tunneling is all in the branch device, so if I understand
things
correctly it is not affected by mst.
BTW, I did a bit more testing on my NUC7i5BNK: for the HDMI output
they
use a MegaChip MCDP2800 DP-to-HDMI converter which according to their
datasheet is supposed to implement CEC Tunneling, but if they do it
is not
exposed as a capability. I'm not sure if it is a MegaChip firmware
issue
or something else. The BIOS is able to do some CEC, but whether
they hook
into the MegaChip or have the CEC pin connected to a GPIO or
something and
have their own controller is something I do not know.
If anyone can clarify what Intel did on the NUC, then that would be
very
helpful.
It's called LSPCON, see i915/intel_lspcon.c, basically to support HDMI
2.0. Currently we only use it in PCON mode, shows up as DP for us. It
could be used in LS mode, showing up as HDMI 1.4, but we don't support
that in i915.
I don't know about the CEC on that.
My NUC6i7KYK has the MCDP2850 LSPCON and it does support CEC over Aux.
The release notes for the NUC state that there is a BIOS configuration
option for enabling support. My doesn't have the option but the LSPCON
fully supports CEC.
What is the output of:
dd if=/dev/drm_dp_aux0 of=aux0 skip=12288 ibs=1 count=48
od -t x1 aux0
Assuming drm_dp_aux0 is the aux channel for the HDMI output on your NUC.
If the first byte is != 0x00, then it advertises CEC over Aux.
For me it says 0x00.
slightly different command, but it still dumps DPCD 0x3000 for 48 bytes.
sudo dd if=/dev/drm_dp_aux0 bs=1 skip=12288 count=48 | hexdump -C
00000000 07 00 00 00 00 00 00 00 00 00 00 00 00 00 00 80
|................|
00000010 f8 23 c4 8f 06 d8 59 7b 37 bb 1e 14 9c cb cd 88
|.#....Y{7.......|
00000020 4e 84 10 00 04 00 f7 f5 e2 fa a3 30 ad 42 ed 19
|N..........0.B..|
When you say "it does support CEC over Aux", does that mean you have
actually
tested it somehow? The only working solution I have seen mentioned for
the
NUC6i7KYK is a Pulse-Eight adapter.
With the NUC7i Intel made BIOS support for CEC, but it is not at all
clear to me if they used CEC tunneling or just hooked up the CEC pin to
some microcontroller.
The only working chipset I have seen is the Parade PS176.
I have a couple PS176 based devices that I purchased from Amazon that do
not work even though they advertise support at DPCD 0x3000.
Club 3D USB-C->HDMI 2.0 UHD
Uptab USB-C->HDMI 2.0
-Clint
Regards,
Hans
-Clint
BR,
Jani.
It would be so nice to get MegaChip CEC Tunneling working on the
NUC, because
then you have native CEC support without requiring any Pulse Eight
adapter.
And add a CEC-capable USB-C to HDMI adapter and you have it on the
USB-C
output as well.
Regards,
Hans
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