[Intel-gfx] [RFC PATCH 0/7] drm/i915: add support for DisplayPort CEC-Tunneling-over-AUX
Hans Verkuil
hverkuil at xs4all.nl
Thu May 25 15:56:38 UTC 2017
On 05/25/2017 05:30 PM, Mike Lothian wrote:
> Hi
>
> Sorry if this is off topic, I've got a Skylake Dell laptop with a USB-C connector and no displayport
>
> Which USB-C -> HDMI-2.0 connector do you recommend for stuff just working based on your testing?
>
> I've been putting off buying one until I knew 4K at 60Hz would work, CEC would be nice to have too
We have done a lot of testing of USB-C to HDMI adapters and many are awful.
Admittedly, we have a special requirement that the adapter shouldn't enable HDCP if
the sink doesn't support HDCP. For whatever reason many of these adapters enable HDCP
regardless, making them useless for video conferencing where you are not allowed to
share HDCP encrypted video. Besides that issue many also have bad signal integrity
or the voltage of the 5V pin is below the allowed minimum voltage.
The best is the Club 3D CAC-1504, but that is one that doesn't hook up the
CEC pin :-( That's a shame since this one was fully within the HDMI specifications.
If you want CEC, then the Samsung EE-PW700 is best.
BTW, the Kramer adapter I mentioned below is indeed the ADC-U31C/HF model.
There are some more adapters that I can test next week, and I'll see if I can also
test a bunch of (mini-)DP to HDMI adapters.
Regards,
Hans
>
> Thanks
>
> Mike
>
> On Thu, 25 May 2017 at 16:06 Hans Verkuil <hverkuil at xs4all.nl <mailto:hverkuil at xs4all.nl>> wrote:
>
> From: Hans Verkuil <hans.verkuil at cisco.com <mailto:hans.verkuil at cisco.com>>
>
> This patch series adds support for the DisplayPort CEC-Tunneling-over-AUX
> protocol.
>
> This patch series is based on v4.12-rc2.
>
> The first four patches add support for a new CEC capability which is
> needed for these devices and for two helper functions.
>
> Then the DP CEC registers are added using Clint's patch.
>
> The core CEC tunneling support is added to drm_dp_cec.c.
>
> And finally this is hooked up in the i915 driver.
>
> Ideally the cec driver is created and destroyed whenever the DP-to-HDMI
> adapter is connected/disconnected, but I have not been a able to find
> a way to distinguish between connecting/disconnecting the HDMI cable
> and connecting/disconnecting the actual DP-to-HDMI adapter.
>
> My current approach is to check the CEC tunneling support whenever a new
> display is connected:
>
> - if CEC tunneling is supported, but no CEC adapter exists, then create one.
> - if CEC tunneling is not supported, then unregister the CEC adapter if one
> was created earlier.
> - if CEC tunneling is supported and the capabilities are identical to the
> existing CEC adapter, then leave it be.
> - if CEC tunneling is supported and the capabilities are different to the
> existing CEC adapter, then unregister that CEC adapter and register a
> new one.
>
> This works well, but it would be much nicer if I would just know when the
> DP adapter is disconnected as opposed to when the HDMI cable is disconnected
> from the adapter. Suggestions are welcome.
>
> The other remaining problem is that there are DP/USB-C to HDMI adapters that
> support CEC tunneling in the chipset, but where the CEC pin is simply never
> hooked up. From the point of view of the driver CEC is supported, but you'll
> never see any other devices.
>
> I am considering sending a CEC POLL message to logical address 0 (the TV)
> to detect if the CEC pin is connected, but this is not 100% guaranteed to
> work. This can be put under a kernel config option, though.
>
> I think I need to do something for this since of the 5 USB-C to HDMI
> adapters I've tested that set the CEC tunneling capability, only 2 have
> the CEC pin hooked up. So this seems to be quite common.
>
> I have tested this with my Intel NUC7i5BNK and with the two working
> USB-C to HDMI adapters that I have found:
>
> a Samsung EE-PW700 adapter and a Kramer ADC-U31C/HF adapter (I think that's
> the model, I need to confirm this).
>
> As usual the specifications of these adapters never, ever tell you whether
> this is supported or not :-( It's trial and error to find one that works. In
> fact, of the 10 USB-C to HDMI adapters I tested 5 didn't support CEC tunneling
> at all, and of the remaining 5 only two had the CEC pin hooked up and so
> actually worked.
>
> BTW, all adapters that supported CEC tunneling used the Parade PS176 chip.
>
> Output of cec-ctl -S (discovers the CEC topology):
>
> $ cec-ctl -S
> Driver Info:
> Driver Name : i915
> Adapter Name : DPDDC-C
> Capabilities : 0x0000007e
> Logical Addresses
> Transmit
> Passthrough
> Remote Control Support
> Monitor All
> Driver version : 4.12.0
> Available Logical Addresses: 4
> Physical Address : 3.0.0.0
> Logical Address Mask : 0x0010
> CEC Version : 2.0
> Vendor ID : 0x000c03 (HDMI)
> OSD Name : 'Playback'
> Logical Addresses : 1 (Allow RC Passthrough)
>
> Logical Address : 4 (Playback Device 1)
> Primary Device Type : Playback
> Logical Address Type : Playback
> All Device Types : Playback
> RC TV Profile : None
> Device Features :
> None
>
> System Information for device 0 (TV) from device 4 (Playback Device 1):
> CEC Version : 1.4
> Physical Address : 0.0.0.0
> Primary Device Type : TV
> Vendor ID : 0x0000f0 (Samsung)
> OSD Name : TV
> Menu Language : eng
> Power Status : On
>
> Topology:
>
> 0.0.0.0 <http://0.0.0.0>: TV
> 3.0.0.0 <http://3.0.0.0>: Playback Device 1
>
> Regards,
>
> Hans
>
> Clint Taylor (1):
> drm/cec: Add CEC over Aux register definitions
>
> Hans Verkuil (6):
> cec: add CEC_CAP_NEEDS_HPD
> cec-ioc-adap-g-caps.rst: document CEC_CAP_NEEDS_HPD
> cec: add cec_s_phys_addr_from_edid helper function
> cec: add cec_phys_addr_invalidate() helper function
> drm: add support for DisplayPort CEC-Tunneling-over-AUX
> drm/i915: add DisplayPort CEC-Tunneling-over-AUX support
>
> .../media/uapi/cec/cec-ioc-adap-g-caps.rst | 8 +
> drivers/gpu/drm/Kconfig | 3 +
> drivers/gpu/drm/Makefile | 1 +
> drivers/gpu/drm/drm_dp_cec.c | 196 +++++++++++++++++++++
> drivers/gpu/drm/i915/Kconfig | 11 ++
> drivers/gpu/drm/i915/intel_dp.c | 46 ++++-
> drivers/media/cec/cec-adap.c | 34 +++-
> drivers/media/cec/cec-api.c | 5 +-
> drivers/media/cec/cec-core.c | 1 +
> include/drm/drm_dp_helper.h | 83 +++++++++
> include/media/cec.h | 15 ++
> include/uapi/linux/cec.h | 2 +
> 12 files changed, 394 insertions(+), 11 deletions(-)
> create mode 100644 drivers/gpu/drm/drm_dp_cec.c
>
> --
> 2.11.0
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org <mailto:dri-devel at lists.freedesktop.org>
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
More information about the Intel-gfx
mailing list