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Marta Lofstedt 3164888a40 drm/i915: Increase poll time for BDW FCLK_DONE
During IGT testing it has been shown that the specification
defined polling time of 1 us for FCLK_DONE, is sometimes not
enough. The issue is still reproducible while disabling
C-states through the PM QoS framework and also while disabling
preemtion. From this the most plausible explanation is that the
issue is due to a firmware flaw.
As a workaround, it is better to wait a little bit longer for
the FCLK_DONE to come around, than to leave with an DRM_ERROR
and having FCLK_DONE at a randome time after.
While spinning a list of igt tests prone to reproduce the issue
the FCLK_DONE poll failed at approximately 2% of the invocations
of the bdw_set_cdclk function. The longest poll time during this
testing was measured to ~7us. So, the suggested new poll time of
100us is on the safe side.

v2: Added more documentation about investigations done.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102243
Signed-off-by: Marta Lofstedt <marta.lofstedt@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170908132829.6312-1-marta.lofstedt@intel.com
2017-09-12 12:19:57 +03:00
arch ummary: 2017-08-29 10:37:36 +10:00
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Documentation dt-bindings: exynos5433-decon: remove i80-if-timings property 2017-08-25 11:58:08 +09:00
drivers drm/i915: Increase poll time for BDW FCLK_DONE 2017-09-12 12:19:57 +03:00
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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
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There are various text files in the Documentation/ subdirectory,
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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
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the problems which may result by upgrading your kernel.