Re: [PATCH] libata-core: Don't have screaming fits over DF/ERR combinations

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Jeff Garzik wrote:

>>> Some hardware seems to get this wrong in a non-harmful way, and there 
>>> are
>>> some devices that seem to do it deliberately for various reasons.

>>> Just take it as a device error not a catastrophic state machine
>>> explosion. 

>>> Signed-off-by: Alan Cox <alan@redhat.com>

>>> diff -u --exclude-from /usr/src/exclude --new-file --recursive 
>>> linux.vanilla-2.6.23-mm1/drivers/ata/libata-core.c 
>>> linux-2.6.23-mm1/drivers/ata/libata-core.c
>>> --- linux.vanilla-2.6.23-mm1/drivers/ata/libata-core.c    2007-10-15 
>>> 15:03:26.000000000 +0100
>>> +++ linux-2.6.23-mm1/drivers/ata/libata-core.c    2007-10-15 
>>> 15:13:49.000000000 +0100
>>> @@ -5258,7 +5319,15 @@
>>>          if (unlikely(status & (ATA_ERR | ATA_DF))) {
>>>              ata_port_printk(ap, KERN_WARNING, "DRQ=1 with device "
>>>                      "error, dev_stat 0x%X\n", status);
>>> -            qc->err_mask |= AC_ERR_HSM;
>>> +            /* Some devices muck this up. Some follow an ATA
>>> +               non-standard that permits the damaged sector to
>>> +               be retrieved at this point. The ATA spec says
>>> +               we should jump up and down on DRQ + ERR, reality

>>    I've always thought that setting both DRQ and ERR is perfectly 
>> valid (well, maybe it's become invalid since ATAPI-4 where all these 
>> state transition flow charts have made its first appearance, to be 
>> quickly replaced by the state diagrams :-) -- I'm too lazy to check 
>> now... :-)

> DRQ+ERR is valid, and SRST (or hard reset) is defined as the method of 
> kicking the device out of that state.

    Well, in the times of old, reading a sector (or group of them for multiple 
mode) was valid for that purpose, wasn't it?

>     Jeff

MBR, Sergei