Laurent Pinchart 9144adc5e5 drm: rcar-du: Cache DSYSR value to ensure known initial value
DSYSR is a DU channel register that also contains group fields. It is
thus written to by both the group and CRTC code, using read-update-write
sequences. As the register isn't initialized explicitly at startup time,
this can lead to invalid or otherwise unexpected values being written to
some of the fields if they have been modified by the firmware or just
not reset properly.

To fix this we can write a fully known value to the DSYSR register when
turning a channel's functional clock on. However, the mix of group and
channel fields complicate this. A simpler solution is to cache the
register and initialize the cached value to the desired hardware
defaults.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
2018-09-25 00:41:04 +03:00
2018-09-02 14:37:30 -07:00

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.
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.
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