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ELANSC(4) |
Kernel Interfaces Manual (i386) |
ELANSC(4) |
NAME
elansc — AMD Elan SC520 System Controller driver
SYNOPSIS
elansc* at mainbus? bus ?
gpio* at elansc?
pci* at elansc?
elanpar* at elansc?
elanpex* at elansc?
DESCRIPTION
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:
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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.
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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 elanpex(4).
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RAM write-protection. The SC520 microcontroller can designate write-protected regions of RAM using the Programmable Address Regions registers. See elanpar(4).
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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.
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PCI host-bridge optimization. elansc takes advantage of a suspend/resume cycle to tune the PCI host-bridge for higher performance.
HISTORY
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.
AUTHORS
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.