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Atm disabling either DP or eDP outputs can generate a spurious short pulse interrupt. The reason is that after disabling the port the source will stop sending a valid stream data, while the sink expects either a valid stream or the idle pattern. Since neither of this is sent the sink assumes (after an arbitrary delay) that the link is lost and requests for link retraining with a short pulse. The spurious pulse is a real problem at least for eDP panels with long power-off / power-cycle delays: as part of disabling the output we disable the panel power. The subsequent spurious short pulse handling will have to turn the power back on, which means the driver has to do a redundant wait for the power-off and power-cycle delays. During system suspend this leads to an unnecessary delay up to ~1s on systems with such panels as reported by Rui. To fix this put the sink to DPMS D3 state before turning off the port. According to the DP spec in this state the sink should not request retraining. This is also what we do already on pre-ddi platforms. As an alternative I also tried configuring the port to send idle pattern - which is against BSPec - and leave the port in normal mode before turning off the port. Neither of these resolved the problem. Cc: Zhang Rui <rui.zhang@intel.com> Cc: David Weinehall <david.weinehall@linux.intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Reported-and-tested-by: Zhang Rui <rui.zhang@intel.com> Signed-off-by: Imre Deak <imre.deak@intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1496250335-7627-1-git-send-email-imre.deak@intel.com
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.