1*4882a593Smuzhiyun.. include:: <isonum.txt> 2*4882a593Smuzhiyun 3*4882a593Smuzhiyun============ 4*4882a593SmuzhiyunSM501 Driver 5*4882a593Smuzhiyun============ 6*4882a593Smuzhiyun 7*4882a593Smuzhiyun:Copyright: |copy| 2006, 2007 Simtec Electronics 8*4882a593Smuzhiyun 9*4882a593SmuzhiyunThe Silicon Motion SM501 multimedia companion chip is a multifunction device 10*4882a593Smuzhiyunwhich may provide numerous interfaces including USB host controller USB gadget, 11*4882a593Smuzhiyunasynchronous serial ports, audio functions, and a dual display video interface. 12*4882a593SmuzhiyunThe device may be connected by PCI or local bus with varying functions enabled. 13*4882a593Smuzhiyun 14*4882a593SmuzhiyunCore 15*4882a593Smuzhiyun---- 16*4882a593Smuzhiyun 17*4882a593SmuzhiyunThe core driver in drivers/mfd provides common services for the 18*4882a593Smuzhiyundrivers which manage the specific hardware blocks. These services 19*4882a593Smuzhiyuninclude locking for common registers, clock control and resource 20*4882a593Smuzhiyunmanagement. 21*4882a593Smuzhiyun 22*4882a593SmuzhiyunThe core registers drivers for both PCI and generic bus based 23*4882a593Smuzhiyunchips via the platform device and driver system. 24*4882a593Smuzhiyun 25*4882a593SmuzhiyunOn detection of a device, the core initialises the chip (which may 26*4882a593Smuzhiyunbe specified by the platform data) and then exports the selected 27*4882a593Smuzhiyunperipheral set as platform devices for the specific drivers. 28*4882a593Smuzhiyun 29*4882a593SmuzhiyunThe core re-uses the platform device system as the platform device 30*4882a593Smuzhiyunsystem provides enough features to support the drivers without the 31*4882a593Smuzhiyunneed to create a new bus-type and the associated code to go with it. 32*4882a593Smuzhiyun 33*4882a593Smuzhiyun 34*4882a593SmuzhiyunResources 35*4882a593Smuzhiyun--------- 36*4882a593Smuzhiyun 37*4882a593SmuzhiyunEach peripheral has a view of the device which is implicitly narrowed to 38*4882a593Smuzhiyunthe specific set of resources that peripheral requires in order to 39*4882a593Smuzhiyunfunction correctly. 40*4882a593Smuzhiyun 41*4882a593SmuzhiyunThe centralised memory allocation allows the driver to ensure that the 42*4882a593Smuzhiyunmaximum possible resource allocation can be made to the video subsystem 43*4882a593Smuzhiyunas this is by-far the most resource-sensitive of the on-chip functions. 44*4882a593Smuzhiyun 45*4882a593SmuzhiyunThe primary issue with memory allocation is that of moving the video 46*4882a593Smuzhiyunbuffers once a display mode is chosen. Indeed when a video mode change 47*4882a593Smuzhiyunoccurs the memory footprint of the video subsystem changes. 48*4882a593Smuzhiyun 49*4882a593SmuzhiyunSince video memory is difficult to move without changing the display 50*4882a593Smuzhiyun(unless sufficient contiguous memory can be provided for the old and new 51*4882a593Smuzhiyunmodes simultaneously) the video driver fully utilises the memory area 52*4882a593Smuzhiyungiven to it by aligning fb0 to the start of the area and fb1 to the end 53*4882a593Smuzhiyunof it. Any memory left over in the middle is used for the acceleration 54*4882a593Smuzhiyunfunctions, which are transient and thus their location is less critical 55*4882a593Smuzhiyunas it can be moved. 56*4882a593Smuzhiyun 57*4882a593Smuzhiyun 58*4882a593SmuzhiyunConfiguration 59*4882a593Smuzhiyun------------- 60*4882a593Smuzhiyun 61*4882a593SmuzhiyunThe platform device driver uses a set of platform data to pass 62*4882a593Smuzhiyunconfigurations through to the core and the subsidiary drivers 63*4882a593Smuzhiyunso that there can be support for more than one system carrying 64*4882a593Smuzhiyunan SM501 built into a single kernel image. 65*4882a593Smuzhiyun 66*4882a593SmuzhiyunThe PCI driver assumes that the PCI card behaves as per the Silicon 67*4882a593SmuzhiyunMotion reference design. 68*4882a593Smuzhiyun 69*4882a593SmuzhiyunThere is an errata (AB-5) affecting the selection of the 70*4882a593Smuzhiyunof the M1XCLK and M1CLK frequencies. These two clocks 71*4882a593Smuzhiyunmust be sourced from the same PLL, although they can then 72*4882a593Smuzhiyunbe divided down individually. If this is not set, then SM501 may 73*4882a593Smuzhiyunlock and hang the whole system. The driver will refuse to 74*4882a593Smuzhiyunattach if the PLL selection is different. 75