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
--- a/drivers/ide/legacy/ide-cs.c 2005-08-08 15:30:35.000000000 +0200
+++ b/drivers/ide/legacy/ide-cs.c 2005-09-05 02:09:47.000000000 +0200
@@ -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);
Signed-off-by: Thomas Kleffel <[email protected]>
Best regards,
Thomas
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