NAME

     altera_sdcard — driver for the Altera University Program Secure Data Card IP Core

SYNOPSIS

     device altera_sdcard

     In /boot/device.hints:
     hint.altera_sdcardc.0.at="nexus0"
     hint.altera_sdcardc.0.maddr=0x7f008000
     hint.altera_sdcardc.0.msize=0x400

DESCRIPTION

     The altera_sdcard device driver provides support for the Altera University Program Secure
     Data Card (SD Card) IP Core device.  A controller device, altera_sdcardcX, will be attached
     during boot.  Inserted disks are presented as disk(9) devices, altera_sdcardX, corresponding
     to the controller number.

HARDWARE

     The current version of the altera_sdcard driver supports the SD Card IP core as described in
     the August 2011 version of Altera's documentation.  The core supports only cards up to 2G
     (CSD 0); larger cards, or cards using newer CSD versions, will not be detected.  The IP core
     has two key limitations: a lack of interrupt support, requiring timer-driven polling to
     detect I/O completion, and support for only single 512-byte block read and write operations
     at a time.  The combined effect of those two limits is that the system clock rate, HZ, must
     be set to at least 200 in order to accomplish the maximum 100KB/s data rate supported by the
     IP core.

SEE ALSO

     disk(9)

     Altera University Program Secure Data Card IP Core, Altera Corporation - University Program,
     ftp://ftp.altera.com/up/pub/Altera_Material/11.0/University_Program_IP_Cores/Memory/SD_Card_Interface_for_SoPC_Builder.pdf,
     August 2011.

HISTORY

     The altera_sdcard device driver first appeared in FreeBSD 10.0.

AUTHORS

     The altera_sdcard device driver and this manual page were developed by SRI International and
     the University of Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
     (“CTSRD”), as part of the DARPA CRASH research programme.  This device driver was written by
     Robert N. M. Watson.

BUGS

     altera_sdcard contains a number of work-arounds for IP core bugs.  Perhaps most critically,
     altera_sdcard ignores the CRC error bit returned in the RR1 register, which appears to be
     unexpectedly set by the IP core.

     altera_sdcard uses fixed polling intervals are used for card insertion/removal and I/O
     completion detection; an adaptive strategy might improve performance by reducing the latency
     to detecting completed I/O.  However, in our experiments, using polling rates greater than
     200 times a second did not improve performance.

     altera_sdcard supports only a nexus bus attachment, which is appropriate for system-on-chip
     busses such as Altera's Avalon bus.  If the IP core is configured off of another bus type,
     then additional bus attachments will be required.