CPU_ELAN -- AMD Elan 520 CPU support
options CPU_ELAN
options CPU_ELAN_PPS
options CPU_ELAN_XTAL
machdep.elan_gpio_config
machdep.elan_freq
options CPU_SOEKRIS
The options CPU_ELAN enables support for the AMD Elan 520 CPU.
A device /dev/elan-mmcr exports the MMCR register bank to userland using
mmap(2).
The i8254 timer will be adjusted to the slightly unorthodox frequency
1189161 Hz (32768 * 45 * 25 / 31) employed by the Elan.
A timecounter named ``ELAN'' is implemented using the general purpose
timer 2, but it will not be usable unless HZ is configured at 150 or
higher. This timecounter is much better than the ``i8254'' timecounter
and should be used at all times.
The machdep.elan_gpio_config sysctl(8) variable enables configuration of
the GPIO pins of the CPU. The string must be exactly 32 characters long.
A `-' means the GPIO is unavailable. A `l' (lower-case ell) configures a
led(4) device (active low). A `L' configures a led(4) device (active
high). A `.' means no configuration for this GPIO. These led(4) devices
will be named /dev/led/gpio%d. For meaning of `P', `e' and `E', see
under options CPU_ELAN_PPS.
The options CPU_ELAN_XTAL and the machdep.elan_freq sysctl(8) variable
can be used to set the CPU clock crystal frequency in Hz. The default is
33333333 Hz.
The options CPU_ELAN_PPS enables precision timestamping using the RFC2783
PPS-API via the /dev/elan-mmcr device. The resolution will be approximately
125 nsec and the precision +- 125 nsec. (For 125 nsec read ``4 /
CPU clock crystal frequency''.)
The input signal must be connected to the TMR1IN pin and a GPIO pin. The
GPIO pin must be configured with a `P' in machdep.elan_gpio_config.
In addition, one GPIO pin can be configured with either `e' (active low)
or `E' (active high) to become a ``echo'' output of the input signal.
Please notice that this signal is not suitable for calibration.
If the options CPU_SOEKRIS is given, the support will additionally be
tailored to the Soekris Engineering 45xx series of embedded computers.
The ``error'' led will be configured (as /dev/led/error) and the GPIO
pins which are not available will be disabled.
led(4), sysctl(8)
The CPU_ELAN code first appeared in FreeBSD 4.7.
Poul-Henning Kamp <[email protected]>
FreeBSD 5.2.1 November 23, 2003 FreeBSD 5.2.1 [ Back ] | 