8bc2f5c3c5
Currently we consider the max vswing reached when we transmit a the max voltage level, but we don't consider pre-emphasis at all. This kinda matches older DP specs that only had some vague text about transmitting the maximum voltage swing. Latest versions now say something vague about consider the sum of the vswing and pre-emphasis fields in the ADJUST_REQUEST_LANE registers. Very vague, and super confusing especially the fact that it talks about transmitted voltgage swing in the same sentence as it say to look at the requested values. Also glanced at the link CTS spec, and that one seems to have tests that assume contradicting behaviour. Some say to consider just the vswing level we transmit, others say to check for sum of transmitted vswing+preemph being 3. So let's try to take some kind of sane middle ground here. I think what could make sense is only consider max vswing reached if MAX_SWING_REACHED==1 _and_ vswing+preemph==3. That will allow things to go all the way up to vswing 3 + pre-emph 0 or vswing 2 + pre-emph 1, depending on what the maximum supported vswing is. Only considering the sum of vswing+pre-emph doesn't make much sense to me since we could terminate too early if the sink requests eg. vswing 0 + pre-emph 3. And if we'd stick to the current code we could terminate too early of the sink asks for vswing 2 + pre-emph 0 when vswing level 3 is not supported. Side note: I don't really understand why any of this stuff is "specified" at all. There is already a limit of 5 attempts at the same vswing+pre-emph level, and a total limit of 10 attempts. So might as well stick to the same max 5 attempts across the board IMO. Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20211004170535.4173-2-ville.syrjala@linux.intel.com Reviewed-by: Imre Deak <imre.deak@intel.com> |
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| LICENSES | ||
| arch | ||
| block | ||
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| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
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| Kbuild | ||
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| Makefile | ||
| README | ||
README
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.