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Documentation / SM501.txt

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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

1	.. include:: <isonum.txt>
3	============
4	SM501 Driver
5	============
7	:Copyright: |copy| 2006, 2007 Simtec Electronics
9	The Silicon Motion SM501 multimedia companion chip is a multifunction device
10	which may provide numerous interfaces including USB host controller USB gadget,
11	asynchronous serial ports, audio functions, and a dual display video interface.
12	The device may be connected by PCI or local bus with varying functions enabled.
14	Core
15	----
17	The core driver in drivers/mfd provides common services for the
18	drivers which manage the specific hardware blocks. These services
19	include locking for common registers, clock control and resource
20	management.
22	The core registers drivers for both PCI and generic bus based
23	chips via the platform device and driver system.
25	On detection of a device, the core initialises the chip (which may
26	be specified by the platform data) and then exports the selected
27	peripheral set as platform devices for the specific drivers.
29	The core re-uses the platform device system as the platform device
30	system provides enough features to support the drivers without the
31	need to create a new bus-type and the associated code to go with it.
34	Resources
35	---------
37	Each peripheral has a view of the device which is implicitly narrowed to
38	the specific set of resources that peripheral requires in order to
39	function correctly.
41	The centralised memory allocation allows the driver to ensure that the
42	maximum possible resource allocation can be made to the video subsystem
43	as this is by-far the most resource-sensitive of the on-chip functions.
45	The primary issue with memory allocation is that of moving the video
46	buffers once a display mode is chosen. Indeed when a video mode change
47	occurs the memory footprint of the video subsystem changes.
49	Since video memory is difficult to move without changing the display
50	(unless sufficient contiguous memory can be provided for the old and new
51	modes simultaneously) the video driver fully utilises the memory area
52	given to it by aligning fb0 to the start of the area and fb1 to the end
53	of it. Any memory left over in the middle is used for the acceleration
54	functions, which are transient and thus their location is less critical
55	as it can be moved.
58	Configuration
59	-------------
61	The platform device driver uses a set of platform data to pass
62	configurations through to the core and the subsidiary drivers
63	so that there can be support for more than one system carrying
64	an SM501 built into a single kernel image.
66	The PCI driver assumes that the PCI card behaves as per the Silicon
67	Motion reference design.
69	There is an errata (AB-5) affecting the selection of the
70	of the M1XCLK and M1CLK frequencies. These two clocks
71	must be sourced from the same PLL, although they can then
72	be divided down individually. If this is not set, then SM501 may
73	lock and hang the whole system. The driver will refuse to
74	attach if the PLL selection is different.
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