Re: Using PATA Platform Driver to access Memory Mapped CF Card

[Graeme Russ <graeme.russ@gmail.com>]

Alan Cox wrote:
> On Sat, 01 May 2010 17:13:47 +1000
> Graeme Russ <graeme.russ@gmail.com> wrote:
> 
>> Hello,
>>
>> I have a CF slot mapped to a GP bus on a board I'm porting linux to. It is
>> wired in 8-bit Memory Mode only with only A0 - A3 mapped from the address
>> bus (starting at 0x20000000). I know the arrangement works as this board is
>> successfully accessing CF cards using existing proprietary firmware.
> 
> Our ATA/IDE driver stack only supports 16/32bit accesses for data. You
> can override the data_xfer methods in a driver to do 8bit transfers. That
> may be one problem you are seeing I guess.
> 

Bingo! Thanks - I simply hacked:

    ioread16_rep(data_addr, buf, words);
to:
    ioread8_rep(data_addr, buf, buflen);

(and similarly for the writes) in ata_sff_data_xfer() and it all "just
works (tm)":

[    2.106837] ata1.00: CFA: SanDisk SDCFH-1024, HDX 4.04, max PIO4
[    2.109659] ata1.00: 2001888 sectors, multi 0: LBA
[    2.111034] ata1.00: configured for PIO
[    2.114811] ata1.00: configured for PIO
[    2.116445] ata1: EH complete
[    2.130852] scsi 0:0:0:0: Direct-Access     ATA      SanDisk SDCFH-10
HDX  PQ: 0 ANSI: 5
[    2.150821] sd 0:0:0:0: [sda] 2001888 512-byte logical blocks: (1.02
GB/977 MiB)
[    2.158847] sd 0:0:0:0: [sda] Write Protect is off
[    2.161977] sd 0:0:0:0: [sda] Write cache: disabled, read cache:
enabled, doesn't support DPO or FUA
[    2.177842]  sda: sda1
[    2.205838] sd 0:0:0:0: [sda] Attached SCSI removable disk

Now to do things right - I've traced everything back into
pata_platform_port_ops (.sff_data_xfer = ata_sff_data_xfer_noirq). So I
will need to create custom data_xfer_noirq and data_xfer functions for the
8-bit transfers. Is there an elegant way to override pata_platform's use of
ata_sff_data_xfer_noirq or will I need to also write a new version of
pata_platform as well?

Thanks

Graeme