[issue685] cheatcode : nodma for libata

[Christian Vogel]

New submission from Christian Vogel <vogelchr at vogel.cx>:

The "nodma" (or "ide=nodma") kernel parameter doesn't work anymore with libata.
The correct way to specify this is via "libata.force=1:pio4". 1 is the number of
the ata-link, e.g. 1 if your error-messages start with "ata1:00: "...

Explanation:

If your hardwarware doesn't support DMA (e.g. compact-flash card in IDE mode)
you will get several "DMA timeout" errors that gradually downgrade your IDE/ATA
features (UDMA -> MWDMA(1/2) -> PIO) until the errors goes away. This takes
about 1 minute per step and delays boot-time a lot.

---------- Kernel Message: -----------
 sda: {{**<- here, a ~1 Minute delay occurs **}}
<3>ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
ata1.00: cmd c8/00:08:00:00:00/00:00:00:00:00/e0 tag 0 dma 4096 in
         res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
ata1.00: status: { DRDY } 
ata1: soft resetting link
...
ata1.00: limiting speed to PIO4 {{**<- this decreases subsequently...**}}
{{** after several times, normal boot continues **}}

---------- Kernel message with libata.force parameter --------
[    7.463226] ata_piix 0000:00:1f.1: version 2.12
[    7.463762] ata_piix 0000:00:1f.1: setting latency timer to 64
[    7.464170] scsi0 : ata_piix
[    7.465505] scsi1 : ata_piix
[    7.472080] ata1: PATA max UDMA/66 cmd 0x1f0 ctl 0x3f6 bmdma 0xffa0 irq 14
[    7.472184] ata2: PATA max UDMA/66 cmd 0x170 ctl 0x376 bmdma 0xffa8 irq 15
[    7.637126] ata1.00: ATA-0: SMI MODEL, 20071116, max MWDMA2
[    7.637220] ata1.00: 1981728 sectors, multi 0: LBA
[    7.637398] ata1.00: FORCE: xfer_mask set to pio4
[    7.650451] ata1.00: configured for PIO4
[    7.657132] ata1.00: FORCE: xfer_mask set to pio4
[    7.670445] ata1.00: configured for PIO4
[    7.670529] ata1: EH complete
[    7.683485] ata2: port disabled. ignoring.
[    7.697267] scsi 0:0:0:0: Direct-Access     ATA      SMI MODEL        2007
PQ: 0 ANSI: 5

----------
messages: 2279
nosy: vogelchr
priority: wish
status: unread
title: cheatcode : nodma for libata
topic: kernel

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GRML issue tracker <bts at bts.grml.org>
<http://bts.grml.org/grml/issue685>
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