How can I emulate HDMI hotplug

[malikcisse]

Hi,

My company has developed a custom base board based on SECO uQ7 I.MX6 CPU.

Le problem is that HDMI TMDS pins have been connected to an FPGA whereas E-DDC pins have been connected to an HDMI output connector.

Now we want to output i.MX6 HDMI (to the FPGA) even if no monitor is connected (thus hotplug remains 0: off).

Is there a way to emulate the attachment and detachment of the “HDMI display” via software?

in kernel/driver/video/mxc_hdmi.c, there is a function names "mxc_hdmi_hotplug( )" which will execute when user plug in/out HDMI cable but I don't know the underlying interrupt mechanism that triggers this function.

Also how can I submit dummy E-DDC to the i.MX6?

Thank you

[igorpadykov]

Hi malik

I am not aware of ways for hotplug emulation, probably

one can try writing HDMI registers with memtool, like

HDMI_PHY_POL0 bit HPD  polarity

HDMI_PHY_MASK0 bit HPD

memtool is part of imx-test

Index of /buildsources/i/imx-test/imx-test-3.10.17-1.0.0

memtool in /unit_tests not work

Best regards

igor

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[malikcisse]

Hi Igor,

Thank you for the recommendation.

This will not apply in my case since the SECO uQ7 I.MX6 board I am using does not send any HDMI video out if monitor's EDID data has not been set.

I could emulate hotplug but since no EDID data could be read the CPU refuses to send the data.

Now I am checking in the mxc_hdmi.c kernel driver where to insert the code that will completely bypass hotplug and EDID and always send video to the HDMI output. However I could not succeed with this yet. Also I have hard time getting the debug log messages from mxc_hdmi.c even after increasing the console debug level to 8 (echo 8 > /proc/sys/kprint). Any advice could be helpfull.