[Qemu-ppc] macio ide question/bug report

[BALATON Zoltan]

Hello,

I think I've found a bug in the macio ide emulation that causes MorphOS to 
fail when trying to mount its boot cd. But I'd need some help on how to 
fix it because I could not completely understand the workings of dbdma and 
how is it talking to the atapi emulation. Here are some debug logs from 
QEMU to try to demonstrate the problem:

DBDMA: writel 0x0000000000000d0c <= 0x00e5a760
DBDMA: channel 0x1a reg 0x3
DBDMA: dbdma_cmdptr_load 0x00e5a760
ATAPI limit=0x8000 packet: 43 00 00 00 00 00 00 03 24 00 00 00

DBDMA: DBDMA_run_bh
DBDMA: writel 0x0000000000000d00 <= 0x80008000
DBDMA: channel 0x1a reg 0x0
DBDMA:     status 0x00008400
DBDMA: readl 0x0000000000000d00 => 0x80008000
DBDMA: channel 0x1a reg 0x0
DBDMA: DBDMA_run_bh
DBDMA: channel_run
dbdma_cmd 0x7f7919f19c70
    req_count 0x0324
    command 0x3000
    phy_addr 0x00e7f6a4
    cmd_dep 0x00000000
    res_count 0x0000
    xfer_status 0x0000
DBDMA: start_input
DBDMA: addr 0xe7f6a4 key 0x0
pmac_ide_transfer(ATAPI) lba=ffffffff, buffer_index=0, len=324
io_buffer_size = 0
remainder: 0 io->len: 804 size: 20
precopying unaligned 292 bytes to 0xe7f8a4
io->len = 0x200
set remainder to: 0
sector_num=-4 size=20, cmd_cmd=0
atapi_cmd_error: sense=0x5 asc=0x21
done DMA
DBDMA: dbdma_end
DBDMA: conditional_wait
DBDMA: dbdma_cmdptr_save 0x00e5a760
DBDMA: xfer_status 0x00008400 res_count 0x0000

What is happening is that a Read TOC command is sent and I think it tries 
to get the reply with a read command with lba set to -1 which according to 
comments in atapi.c should return results without reading a sector but 
this is erroneously converted to sector -4 in 
macio.c:pmac_ide_atapi_transfer_cb and causes it to fail. My question to 
those who undestand this better if this analysis is correct and how could 
it be fixed?

Regards,
BALATON Zoltan