1 SM501 Driver 2 ============ 3 4Copyright 2006, 2007 Simtec Electronics 5 6Core 7---- 8 9The core driver in drivers/mfd provides common services for the 10drivers which manage the specific hardware blocks. These services 11include locking for common registers, clock control and resource 12management. 13 14The core registers drivers for both PCI and generic bus based 15chips via the platform device and driver system. 16 17On detection of a device, the core initialises the chip (which may 18be specified by the platform data) and then exports the selected 19peripheral set as platform devices for the specific drivers. 20 21The core re-uses the platform device system as the platform device 22system provides enough features to support the drivers without the 23need to create a new bus-type and the associated code to go with it. 24 25 26Resources 27--------- 28 29Each peripheral has a view of the device which is implicitly narrowed to 30the specific set of resources that peripheral requires in order to 31function correctly. 32 33The centralised memory allocation allows the driver to ensure that the 34maximum possible resource allocation can be made to the video subsystem 35as this is by-far the most resource-sensitive of the on-chip functions. 36 37The primary issue with memory allocation is that of moving the video 38buffers once a display mode is chosen. Indeed when a video mode change 39occurs the memory footprint of the video subsystem changes. 40 41Since video memory is difficult to move without changing the display 42(unless sufficient contiguous memory can be provided for the old and new 43modes simultaneously) the video driver fully utilises the memory area 44given to it by aligning fb0 to the start of the area and fb1 to the end 45of it. Any memory left over in the middle is used for the acceleration 46functions, which are transient and thus their location is less critical 47as it can be moved. 48 49 50Configuration 51------------- 52 53The platform device driver uses a set of platform data to pass 54configurations through to the core and the subsidiary drivers 55so that there can be support for more than one system carrying 56an SM501 built into a single kernel image. 57 58The PCI driver assumes that the PCI card behaves as per the Silicon 59Motion reference design. 60 61There is an errata (AB-5) affecting the selection of the 62of the M1XCLK and M1CLK frequencies. These two clocks 63must be sourced from the same PLL, although they can then 64be divided down individually. If this is not set, then SM501 may 65lock and hang the whole system. The driver will refuse to 66attach if the PLL selection is different. 67