elansc
—
AMD Elan SC520 System Controller driver
elansc* at mainbus? bus ?
gpio* at elansc?
pci* at elansc?
elanpar* at elansc?
elanpex* at elansc?
The elansc
driver supports the system controller of the
AMD Elan SC520 microcontroller. The SC520 consists of an AMD Am5x86 processor
core, integrated PCI host controller, and several standard on-chip devices,
such as NS16550-compatible UARTs, real-time clock, and timers.
The Elan SC520 also provides several special on-chip devices. The
following are supported by the elansc
driver:
- Watchdog timer. The watchdog timer may be configured for a 1 second, 2
second, 4 second, 8 second, 16 second, or 32 second expiration
period.
- PCI exceptions reporting. The SC520 microcontroller can report exceptions
that occur as it acts as both a PCI bus master and a bus target. See
i386/elanpex(4).
- RAM write-protection. The SC520 microcontroller can designate
write-protected regions of RAM using the Programmable Address Regions
registers. See
i386/elanpar(4).
- Programmable Input/Output. The SC520 microcontroller supports 32
programmable I/O signals (PIOs) that can be used on the system board to
monitor signals or control devices that are not handled by the other
functions in the SC520 microcontroller. These signals can be programmed to
be inputs or to be driven “high” or “low” as
outputs. Pins can be accessed through the
gpio(4) framework. The
gpioctl(8) program
allows easy manipulation of pins from userland.
- PCI host-bridge optimization.
elansc
takes
advantage of a suspend/resume cycle to tune the PCI host-bridge for higher
performance.
The elansc
device first appeared in
NetBSD 2.0. PIO function support was added in
OpenBSD 3.6, and subsequently ported to
NetBSD 4.0. Support for PCI exceptions reporting and
for RAM write-protection first appeared in NetBSD 5.0.
The elansc
driver was written by Jason
R. Thorpe
<thorpej@NetBSD.org>.
Jasper Wallace provided the work-around for a hardware
bug related to the watchdog timer in some steppings of the SC520 CPU. Support
for the PIO function was added to OpenBSD 3.6 by
Alexander Yurchenko
<grange@openbsd.org>
and was ported to NetBSD by
Jeff Rizzo
<riz@NetBSD.org>.
David Young
<dyoung@NetBSD.org>
added support for PCI exceptions reporting and for RAM write-protection using
the Programmable Address Regions.