Make ide-cs work for hardware with 8-bit CF-Interface

Hello,

it is technically possible to access a CF-Card with an 8-bit width bus.

The problem with the current code is that the IDE code does a 16 (or 32) bit read on the IDE data register. If the bus interface for a 8-bit bus would then do two reads to offsets 0 and 1.

The second read (to offset 1) then reads the error register instead of the data register's odd byte.

To fix this problem I've changed the ide-cs code to use the duplicated data registers at offset 8 and 9 which are not overlapped with anything.

According to the specs, those registers should be there in every CF card. I've tested this with a couple of CFs, including SanDisk, Microdrive and several NoNames.

The specific architechture I'm using this on is a AT91RM9200 with kernel 2.6.13 and the patches from http://maxim.org.za/AT91RM9200/2.6/.

For more information on the overlapped / non-overlapped registers see http://www.compactflash.org/cfspc3_0.pdf - page 96

The following patch is against vanilla 2.6.13.

ldiff -uprN a/drivers/ide/legacy/ide-cs.c b/drivers/ide/legacy/ide-cs.c

@@ -186,7 +186,8 @@ static int idecs_register(unsigned long
 {
     hw_regs_t hw;
     memset(&hw, 0, sizeof(hw));
-    ide_init_hwif_ports(&hw, io, ctl, NULL);
+    ide_std_init_ports(&hw, io, ctl);
+    hw.io_ports[IDE_DATA_OFFSET] = io + 0x08;
     hw.irq = irq;
     hw.chipset = ide_pci;
     return ide_register_hw_with_fixup(&hw, NULL, ide_undecoded_slave);

Best regards,

Thomas

ide-cs handles a lot more than just CF cards so it might not be a wise approach fpr general consumption.