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The source device should ensure the sink is ready before proceeding to read the sink capability or perform any aux transactions. The sink will indicate its readiness by asserting the HPD line. The controller driver needs to wait for the hpd line to be asserted by the sink before it performs any aux transactions. The eDP sink is assumed to be always connected. It needs power from the source and its HPD line will be asserted only after the panel is powered on. The panel power will be enabled from the panel-edp driver and only after that, the hpd line will be asserted. Whereas for DP, the sink can be hotplugged and unplugged anytime. The hpd line gets asserted to indicate the sink is connected and ready. Hence there is no need to wait for the hpd line to be asserted for a DP sink. Signed-off-by: Sankeerth Billakanti <quic_sbillaka@quicinc.com> Reviewed-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Stephen Boyd <swboyd@chromium.org> Patchwork: https://patchwork.freedesktop.org/patch/483312/ Link: https://lore.kernel.org/r/1650887072-16652-4-git-send-email-quic_sbillaka@quicinc.com Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
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.