blob: 882507453ba4ea60fd022d663aefcdc9de40bf35 [file] [log] [blame]
Mauro Carvalho Chehabd1bb1d02017-05-17 08:01:45 -03001.. include:: <isonum.txt>
Ben Dooksffd65af2007-06-23 17:16:31 -07002
Mauro Carvalho Chehabd1bb1d02017-05-17 08:01:45 -03003============
4SM501 Driver
5============
6
7:Copyright: |copy| 2006, 2007 Simtec Electronics
Ben Dooksffd65af2007-06-23 17:16:31 -07008
Rob Landleyf0ae5662007-10-16 23:31:24 -07009The Silicon Motion SM501 multimedia companion chip is a multifunction device
10which may provide numerous interfaces including USB host controller USB gadget,
Matt LaPlante19f59462009-04-27 15:06:31 +020011asynchronous serial ports, audio functions, and a dual display video interface.
Rob Landleyf0ae5662007-10-16 23:31:24 -070012The device may be connected by PCI or local bus with varying functions enabled.
13
Ben Dooksffd65af2007-06-23 17:16:31 -070014Core
15----
16
17The core driver in drivers/mfd provides common services for the
18drivers which manage the specific hardware blocks. These services
19include locking for common registers, clock control and resource
20management.
21
22The core registers drivers for both PCI and generic bus based
23chips via the platform device and driver system.
24
25On detection of a device, the core initialises the chip (which may
26be specified by the platform data) and then exports the selected
27peripheral set as platform devices for the specific drivers.
28
29The core re-uses the platform device system as the platform device
30system provides enough features to support the drivers without the
31need to create a new bus-type and the associated code to go with it.
32
33
34Resources
35---------
36
37Each peripheral has a view of the device which is implicitly narrowed to
38the specific set of resources that peripheral requires in order to
39function correctly.
40
41The centralised memory allocation allows the driver to ensure that the
42maximum possible resource allocation can be made to the video subsystem
43as this is by-far the most resource-sensitive of the on-chip functions.
44
45The primary issue with memory allocation is that of moving the video
46buffers once a display mode is chosen. Indeed when a video mode change
47occurs the memory footprint of the video subsystem changes.
48
49Since video memory is difficult to move without changing the display
50(unless sufficient contiguous memory can be provided for the old and new
51modes simultaneously) the video driver fully utilises the memory area
52given to it by aligning fb0 to the start of the area and fb1 to the end
53of it. Any memory left over in the middle is used for the acceleration
54functions, which are transient and thus their location is less critical
55as it can be moved.
56
57
58Configuration
59-------------
60
61The platform device driver uses a set of platform data to pass
62configurations through to the core and the subsidiary drivers
63so that there can be support for more than one system carrying
64an SM501 built into a single kernel image.
65
66The PCI driver assumes that the PCI card behaves as per the Silicon
67Motion reference design.
68
69There is an errata (AB-5) affecting the selection of the
70of the M1XCLK and M1CLK frequencies. These two clocks
71must be sourced from the same PLL, although they can then
72be divided down individually. If this is not set, then SM501 may
73lock and hang the whole system. The driver will refuse to
74attach if the PLL selection is different.