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

[Jeff Garzik <jgarzik@pobox.com>]

Sergei Shtylyov wrote:
> 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?

Yes, hence the recent FIFO drain patches.

But that doesn't make sense for SATA devices, where the FIFO is really 
emulated, and it works on older PATA devices.

	Jeff