MFP4:
Change 227594 by brooks@brooks_zenith on 2013/04/11 17:10:14
When we fail, print the error that occurred if we are giving
up or if bootverbose is set.
MFP4 (driver change only):
Change 231100 by brooks@brooks_zenith on 2013/07/12 21:01:31
Add a new option ALTERA_SDCARD_FAST_SIM which checks immediately
for success of I/O operations rather than queuing a task.
Sponsored by: DARPA/AFRL
Approved by: re (glebius)
Add a missing 0 to the mask for byte0 of C_SIZE.
The previous mask (0xc) worked except that the last 0-1536K of the disk
could not be accessed since we were shifting the (wrong) bits we did
mask off the right edge.
which can be synthesised in Altera FPGAs. An altera_sdcardc device
probes during the boot, and /dev/altera_sdcard devices come and go as
inserted and removed. The device driver attaches directly to the
Nexus, as is common for system-on-chip device drivers.
This IP core suffers a number of significant limitations, including a
lack of interrupt-driven I/O -- we must implement timer-driven polling,
only CSD 0 cards (up to 2G) are supported, there are serious memory
access issues that require the driver to verify writes to memory-mapped
buffers, undocumented alignment requirements, and erroneous error
returns. The driver must therefore work quite hard, despite a fairly
simple hardware-software interface. The IP core also supports at most
one outstanding I/O at a time, so is not a speed demon.
However, with the above workarounds, and subject to performance
problems, it works quite reliably in practice, and we can use it for
read-write mounts of root file systems, etc.
Sponsored by: DARPA, AFRL
