+++ /dev/null
-README on the Compact Flash for Card Engines
-============================================
-
-There are three challenges in supporting the CF interface of the Card
-Engines. First, every IO operation must be followed with IO to
-another memory region. Second, the slot is wired for one-to-one
-address mapping *and* it is wired for 16 bit access only. Second, the
-interrupt request line from the CF device isn't wired.
-
-The IOBARRIER issue is covered in README.IOBARRIER. This isn't an
-onerous problem. Enough said here.
-
-The addressing issue is solved in the
-arch/arm/mach-lh7a40x/ide-lpd7a40x.c file with some awkward
-work-arounds. We implement a special SELECT_DRIVE routine that is
-called before the IDE driver performs its own SELECT_DRIVE. Our code
-recognizes that the SELECT register cannot be modified without also
-writing a command. It send an IDLE_IMMEDIATE command on selecting a
-drive. The function also prevents drive select to the slave drive
-since there can be only one. The awkward part is that the IDE driver,
-even though we have a select procedure, also attempts to change the
-drive by writing directly the SELECT register. This attempt is
-explicitly blocked by the OUTB function--not pretty, but effective.
-
-The lack of interrupts is a more serious problem. Even though the CF
-card is fast when compared to a normal IDE device, we don't know that
-the CF is really flash. A user could use one of the very small hard
-drives being shipped with a CF interface. The IDE code includes a
-check for interfaces that lack an IRQ. In these cases, submitting a
-command to the IDE controller is followed by a call to poll for
-completion. If the device isn't immediately ready, it schedules a
-timer to poll again later.
git.openpandora.org / pandora-kernel.git / blobdiff