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author | Ben Dooks <ben-linux@fluff.org> | 2007-06-23 17:16:31 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-06-24 08:59:11 -0700 |
commit | ffd65af0e67a054e1e2393c9b0995c03c47cdc30 (patch) | |
tree | 25c7462c8e3ffecfd9f7835581098dec045b49bb | |
parent | 819062219abf8a78e54cad5c1c8716e6c8e7b870 (diff) | |
download | op-kernel-dev-ffd65af0e67a054e1e2393c9b0995c03c47cdc30.zip op-kernel-dev-ffd65af0e67a054e1e2393c9b0995c03c47cdc30.tar.gz |
SM501: Add Documentation/SM501.txt
Add documentation for the SM501 in Documentation/SM501.txt outlining the SM501
driver.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | Documentation/SM501.txt | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/Documentation/SM501.txt b/Documentation/SM501.txt new file mode 100644 index 0000000..3a1bd95 --- /dev/null +++ b/Documentation/SM501.txt @@ -0,0 +1,66 @@ + SM501 Driver + ============ + +Copyright 2006, 2007 Simtec Electronics + +Core +---- + +The core driver in drivers/mfd provides common services for the +drivers which manage the specific hardware blocks. These services +include locking for common registers, clock control and resource +management. + +The core registers drivers for both PCI and generic bus based +chips via the platform device and driver system. + +On detection of a device, the core initialises the chip (which may +be specified by the platform data) and then exports the selected +peripheral set as platform devices for the specific drivers. + +The core re-uses the platform device system as the platform device +system provides enough features to support the drivers without the +need to create a new bus-type and the associated code to go with it. + + +Resources +--------- + +Each peripheral has a view of the device which is implicitly narrowed to +the specific set of resources that peripheral requires in order to +function correctly. + +The centralised memory allocation allows the driver to ensure that the +maximum possible resource allocation can be made to the video subsystem +as this is by-far the most resource-sensitive of the on-chip functions. + +The primary issue with memory allocation is that of moving the video +buffers once a display mode is chosen. Indeed when a video mode change +occurs the memory footprint of the video subsystem changes. + +Since video memory is difficult to move without changing the display +(unless sufficient contiguous memory can be provided for the old and new +modes simultaneously) the video driver fully utilises the memory area +given to it by aligning fb0 to the start of the area and fb1 to the end +of it. Any memory left over in the middle is used for the acceleration +functions, which are transient and thus their location is less critical +as it can be moved. + + +Configuration +------------- + +The platform device driver uses a set of platform data to pass +configurations through to the core and the subsidiary drivers +so that there can be support for more than one system carrying +an SM501 built into a single kernel image. + +The PCI driver assumes that the PCI card behaves as per the Silicon +Motion reference design. + +There is an errata (AB-5) affecting the selection of the +of the M1XCLK and M1CLK frequencies. These two clocks +must be sourced from the same PLL, although they can then +be divided down individually. If this is not set, then SM501 may +lock and hang the whole system. The driver will refuse to +attach if the PLL selection is different. |