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6752bea8b0
[Why] The actual position for the cursor on the screen is essentially: x_out = x - x_plane - x_hotspot y_out = y - y_plane - y_hotspot The register values for cursor position and cursor hotspot need to be greater than zero when programmed, but we also need to subtract off the plane position to display the cursor at the correct position. Since we don't want x or y to be less than zero, we add the plane position as a positive value to x_hotspot or y_hotspot. However, what this doesn't take into account is that the hotspot registers are limited by the maximum cursor size. On DCN10 the cursor hotspot regitsers are masked to 0xFF, so they have a maximum value of 0-255. Values greater this will wrap, causing the cursor to display in the wrong position. In practice this means that for sufficiently large plane positions, the cursor will be drawn twice on the screen, and can cause screen flashes or p-state WARNS depending on what the wrapped value is. So we need a way to remove the value from x_plane and y_plane without exceeding the maximum cursor size. [How] Subtract as much as x_plane/y_plane as possible from x and y and place the remainder in the cursor hotspot register. The value for x_hotspot and y_hotspot can still wrap around but it won't happen in a case where the cursor is actually enabled. The cursor plane needs to intersect at least one pixel of the plane's rectangle to be enabled, so the cursor position + hotspot provided by userspace must always be strictly less than the maximum cursor size for the cursor to actually be enabled. Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com> Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com> Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> |
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| README | ||
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.