Since the current KMS API sets the mode independantly on
each crtc, we may end up with resource conflicts. The PLL
allocation is one of those cases. In the following example
we have 3 crtcs in use driving 2 DVI connectors and 1 DP
connector. On the initial kernel modeset for fbdev, the
display topology ends up as follows:
crtc0 -> DP-0
crtc1 -> DVI-0
crtc2 -> DVI-1
Because this is the first modeset, all of the PLLs are
available as none have been assigned. So we end up with
the following:
crtc0 uses DCPLL
crtc1 uses PPLL2
crtc2 uses PPLL1
When X starts, it assigns a different topology:
crtc0 -> DVI-0
crtc1 -> DP-0
crtc2 -> DVI-1
However, since the KMS API is per crtc, we set the mode on each
crtc independantly. When it comes time to set the mode on crtc0,
the topology for crtc1 and crtc2 are still intact. crtc1 and
crtc2 are already assigned PPLL2 and PPLL1 so when it comes time
to set the mode on crtc0, crtc1 and crtc2 have not been torn down
yet, so there appears to be no PLLs available. In reality, we
are reconfiguring the entire display topology, however, since
each crtc is handled independantly, we don't know that in the
driver at each crtc mode set time.
This patch checks to see if the same connector is being driven by
another crtc, and if so, uses the PLL already associated with it.
v2: store connector in the radeon crtc struct, simplify checking.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html
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