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The idea that ctg uses different HPD live state bits is
total nonsense, at least on my machine (Dell Latitude
E5400).
The only reason DP-B even works on my ctg is that DP-D
live state is stuck high, even though there is no physical
DP-D port. So when the detect checks DP-B live state it
sees the stuck live state of DP-D instead. If I hack
the driver to not register DP-D at all, and thus we never
enabe DP-D HPD, DP-B stops working as well.
Just to put some conclusive evidence into this mess,
here are the actual hotplug register values for each port:
Everything disconnected:
PORT_HOTPLUG_EN (0x00061110): 0x00000000
PORT_HOTPLUG_STAT (0x00061114): 0x00000000
PORT_HOTPLUG_EN (0x00061110): 0x08000000
PORT_HOTPLUG_STAT (0x00061114): 0x08000000
PORT_HOTPLUG_EN (0x00061110): 0x10000000
PORT_HOTPLUG_STAT (0x00061114): 0x00000000
PORT_HOTPLUG_EN (0x00061110): 0x20000000
PORT_HOTPLUG_STAT (0x00061114): 0x00000000
Only port B connected:
PORT_HOTPLUG_EN (0x00061110): 0x00000000
PORT_HOTPLUG_STAT (0x00061114): 0x00000000
PORT_HOTPLUG_EN (0x00061110): 0x08000000
PORT_HOTPLUG_STAT (0x00061114): 0x08000000
PORT_HOTPLUG_EN (0x00061110): 0x10000000
PORT_HOTPLUG_STAT (0x00061114): 0x00000000
PORT_HOTPLUG_EN (0x00061110): 0x20000000
PORT_HOTPLUG_STAT (0x00061114): 0x20000000
Only port C connected:
PORT_HOTPLUG_EN (0x00061110): 0x00000000
PORT_HOTPLUG_STAT (0x00061114): 0x00000000
PORT_HOTPLUG_EN (0x00061110): 0x08000000
PORT_HOTPLUG_STAT (0x00061114): 0x08000000
PORT_HOTPLUG_EN (0x00061110): 0x10000000
PORT_HOTPLUG_STAT (0x00061114): 0x10000000
PORT_HOTPLUG_EN (0x00061110): 0x20000000
PORT_HOTPLUG_STAT (0x00061114): 0x00000000
So the enable bit and live state bit always match 1:1.
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230302161013.29213-4-ville.syrjala@linux.intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.