On Mon, Dec 10, 2018 at 06:07:10PM +0100, Hans Verkuil wrote: > Hi Thierry, > > On 12/10/18 5:00 PM, Thierry Reding wrote: > > From: Thierry Reding <treding@xxxxxxxxxx> > > > > The CEC controller found on Tegra186 and Tegra194 is the same as on > > earlier generations. > > Well... at least for the Tegra186 there is a problem that needs to be addressed first. > No idea if this was solved for the Tegra194, it might be present there as well. > > The Tegra186 hardware connected the CEC lines of both HDMI outputs together. This is > a HW bug, and it means that only one of the two HDMI outputs can use the CEC block. I don't know where you got that information from, but I can't find any indication of that in the documentation. My understanding is that there is a single CEC block that is completely independent and it is merely a decision of the board designer where to connect it. I'm not aware of any boards that expose more than a single CEC. You may already have access to the schematics, if not you can download them here: https://developer.nvidia.com/embedded/dlc/jetson-tx1-tx2-developer-kit-carrier-board-c02-design-files It's slightly annoying because it requires registration. But in those schematics you'll see that the HDMI_CEC pin is just routed directly from the processor module to the connector on the carrier board via the connector. > HDMI inputs CAN share the CEC line, but never outputs. There should have been two > CEC blocks, one for each HDMI output. Like I said, I don't think these are shared. The board design will have to choose which connector gets the SOR and CEC pins for HDMI. Typically the other SOR will be used for DisplayPort, not HDMI, though that would technically be possible. I think in case where there really were two HDMI connectors on a design, a decision would have to be made as to which one gets the CEC pin. > It should not be possible to use the same CEC block for both HDMI > outputs on the 186. Ideally it should be a required dts property that > determines this. I'm not sure where that should happen. One option > might be to use the cec_notifier_get_conn() function so you can > register the CEC adapter for a specific connector only. For older > tegra versions the connector name would be NULL (i.e. don't care), for > the 186 (and perhaps 194) it would be a required property that tells > the CEC driver which connector it is associated with. > > Just a suggestion, there might be other ways to implement this as well. Given the documentation that I have, I don't think we need to take any additional precautions. We just to hook up the CEC controller to the correct HDMI connector via the hdmi-phandle property. > So before I can merge this I need to know first how you plan to handle > this HW bug. I don't think this is an actual bug. It's more of a restriction of the SoC that allows only a single HDMI connector with CEC support. Thierry
Attachment:
signature.asc
Description: PGP signature
