Cortex-A8 port status

General status

At present the port consists of three components:

• A HAL targetting TI’s OMAP3530 system-on-chip.
• A modified version of the RISC OS kernel containing support for Cortex-A8 CPU cores
• Additional custom driver modules, e.g. MUSBDriver, OMAPVideo

One optional component adds some value:

• A disc image including the boot sequence and some applications (not specific to the port, but useful in getting a viable system running)

At present the port is known to be functional on the following hardware devices:

• BeagleBoard
• DevKit8000
• IGEPv2
• BeagleBoard-xM
• Touch Book

In the future, the port is likely to support at least the following additional devices:

• Pandora

In the past, the port has also been used via the QEMU emulator (QEMU-OMAP3, Maemo QEMU). However it is not currently known whether QEMU’s OMAP3 emulation has reached the state where running RISC OS from within QEMU is again feasible.

There is also scope for expanding the port to support other SoC’s made by other manufacturers, e.g. the Freescale i.MX515 . For anyone considering this, refer to How to port RISC OS to new hardware.

Current status

This table lists the current state of all planned major tasks.

Minor todo items and other miscellaneous tasks

• Kernel
• OMAP3 HAL
  • Soft-off/resets:
    • Soft-off is only implemented for TouchBook so far. Implementing true soft-off for other devices seems trivial (IIC write to P1_SW_EVENTS), but since most devices (or the beagleboard, at least) only wires the reset button up to the OMAP it means that there’s no way of restoring power afterwards other than turning it off and on at the wall. So may need to investigate implementing some deep sleep state instead (e.g. everything off except VDD1, and OMAP in sleep state with the reset button set as a wakeup event, which will then trigger code to perform a soft reset upon wakeup)
  • IIC driver needs updating to support speeds > 100kbps
  • DMA driver needs to bundle logical channels in pairs, to allow for double-buffering
    • AM/DM37x has an improved DMA controller that supports arbitrary length transfer lists, would be good to use that functionality where possible.
    • Also need to work out how to handle the DMA packet size – it looks like both the DMA controller and the device need to know the packet size in order for DMA to work correctly?
• RTCAdjust
  • Module needs updating to understand HAL RTC’s before it can be used with the OMAP port
  • Or migrate the RTC code out of the kernel since it doesn’t need it to boot, and combine it with RTCAdjust (supporting Philips/Dallas/OMAP3530/emulated RTCs)
• USB
  • HAL USB enumeration doesn’t work too well; may not even work at all if both HAL & PCI USB controllers are present
  • Need to investigate file corruption issues that people are reporting.
• Power saving
  • Make more stuff call Portable_Idle. Potential candidates:
    • DebugTerminal code that calls HAL_DebugRX (tricky – HAL isn’t likely to use interrupt driven debug I/O. Plus low priority since only developers would be using the code.)
    • IRQ-based IIC ops
    • USB driver tsleep() implementation
  • Need HAL device/API to read temperature sensor(s) – see here
  • Need HAL device/API to read power consumption – see here and the following few posts.
  • Implement Portable_Stop for suspend-to-RAM functionality
  • Come up with sensible API for reading battery state & charge, bearing in mind that AI’s SmartBook will have three different batteries and charging circuits.
  • Investigate ways of improving the sound stack so that the audio hardware can be powered down when not in use.
    • Could easily detect when no sound is being output by examining the audio buffer. Then disable all audio hardware, and switch to one of the OMAP’s timers for generating fake buffer fill requests. But re-enabling everything without causing a big delay (or losing the first few frames of data) could be tricky.
• SCSI
  • Get background transfers working to improve performance. Might make sense to start off by translating SCSIFS into C to make it easier to adapt/maintain/debug.
  • Fix the long mount times, if background transfers don’t. Problem seems to be that lots of sectors are read one at a time.
• Fix the boot sequence/network stack so it doesn’t fail if EtherUSB is in use but no NIC is connected
• Improved ROM packaging
  • SDCreate version 2 that can download suitable x-loader and u-boot files from the internet instead of requiring the user to source his own
  • Change everything over to use uimages by default, or add a ROM checksum check to the HAL? (to fix problems caused by SD cards not being properly dismounted after copying ROMs to them)
• Integrate Absolutely’s functionality with the OS
• Video:
  • Tool to generate MDFs from EDID data
  • HALify *vidcbandwidthlimit
• Update the Debugger module so that it’s smart enough to unprotect ‘ROM’ pages when placing breakpoints. Being able to place breakpoints in ROM is very useful!