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[WHY] When changing the DISPCLK_WDIVIDER value from 126 to 127, the change in clock rate is too great for the FIFOs to handle. This can cause visible corruption during clock change. HW has handed down this register sequence to fix the issue. [HOW] The sequence, from HW: a. 127 -> 126 Read DIG_FIFO_CAL_AVERAGE_LEVEL FIFO level N = DIG_FIFO_CAL_AVERAGE_LEVEL / 4 Set DCCG_FIFO_ERRDET_OVR_EN = 1 Write 1 to OTGx_DROP_PIXEL for (N-4) times Set DCCG_FIFO_ERRDET_OVR_EN = 0 Write DENTIST_DISPCLK_RDIVIDER = 126 Because of frequency stepping, sequence a can be executed to change the divider from 127 to any other divider value. b. 126 -> 127 Read DIG_FIFO_CAL_AVERAGE_LEVEL FIFO level N = DIG_FIFO_CAL_AVERAGE_LEVEL / 4 Set DCCG_FIFO_ERRDET_OVR_EN = 1 Write 1 to OTGx_ADD_PIXEL for (12-N) times Set DCCG_FIFO_ERRDET_OVR_EN = 0 Write DENTIST_DISPCLK_RDIVIDER = 127 Because of frequency stepping, divider must first be set from any other divider value to 126 before executing sequence b. Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com> Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com> Acked-by: Anson Jacob <Anson.Jacob@amd.com> Tested-by: Daniel Wheeler <daniel.wheeler@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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.