Re: libata machine check on Alpha

[Tejun Heo <htejun@gmail.com>]

Jeff Garzik wrote:
> Albert Lee wrote:
>> Per Jeff's comment, there is a document on t13 
>> (http://www.t13.org/docs2003/e03131r0.pdf).
>> The documents reads:
>> "Eg. – Word 50, bit 13: Set to 1 for devices that support DMAIN bit in 
>> Features Register for Packet Command".
>> However, this looks more for the ATAPI device than for the bridge?
>> Also it looks not a t13 standard yet?
>> Can we use this word 50 to identify 3611/3811?
> 
> 
> DMADIR is in my copy of ATA-7...
> 

Here's the relavant part from ATA8 draft.  It seems that the bridge is 
supposed to mangle the IDENTIFY PACKET DEVICE result.  It's supposed to 
nuke all DMA transfer mode information reported from the original device 
and report supported modes from the view point of the bridge in bits 
10:1 (which, BTW, should be all 1's).

The question is whether or not bridges implement this properly. I think 
we can add a printk to word 62 and ask Jonathan to test it.

----

7.18.6.17 Word 62: DMADIR

ATAPI devices that use a serial ATA bridge chip for connection to a 
serial ATA host may require use of the DMADIR bit to indicate transfer 
direction for Packet DMA commands. Word 62 is used to indicate if such
support is required.

If bit 15 of word 62 is set to one, then DMADIR bit in the Packet 
Command is required by the device for Packet DMA and Bits 2:0 of word 
63, bits 15 and 8 in word 49, and bits 6:0 of word 88 shall be cleared 
to 0,.

If bit 15 of word 62 is cleared to 0, DMADIR bit in the PACKET command 
is not required. If bit 15 of word 62 is cleared to zero, then all bits 
of word 62 shall be cleared to zero.

Bits (14:11) are reserved.

Bits (10:1) indicate DMA mode support. Since the DMADIR bit is only used 
for a Serial ATAPI device, all of these bits are set to 1.

-- 
tejun