Re: [git-patches] EH, irq-pio merge and NCQ patches

[Jeff Garzik <jgarzik@pobox.com>]

Tejun Heo wrote:
> Jeff Garzik wrote:
>> Tejun Heo wrote:
>>> I didn't add DMA engine stopping to ata_bmdma_freeze() in this series.
>>> When BMDMA engine is turned off, all status bits go too.  However, the
>>> status is used by BMDMA EH to report and to recognize host bus error
>>> reprsented as timeout.
>>>
>>> To make all of them work, the BMDMA status needs to be stored in
>>> ata_bmdma_freeze() and used in EH, which is currently a bit difficult
>>> to implement for generic BMDMA.  I think we can resolve this later.
>>
>> Agree re storing BMDMA status.  The very next operation needs to be 
>> DMA-stop, though.  Otherwise shadow register block isn't accessible. 
>> And you must still check BMDMA status -after- stopping DMA, too (that 
>> doesn't invalidate your logic quoted above, of course).
> 
> I see.  I think this can be done by making all BMDMA related stuff into 
> a layer between highlevel libata and BMDMA LLDDs.  We can move all IO 
> ops into that layer and newer controllers like ahci, sata_sil24 and 
> sata_mv don't have to care about them.  Have yet to think about how to 
> do it in simple way though, such that changes to BMDMA LLDDs are minimal.

In an ideal world, drivers would register themselves as BMDMA drivers 
rather than libata drivers.  Move all the BMDMA hooks to a separate 
structure, leaving only the high level ->qc_issue() interface in 
ata_port_operations.


>> BTW, it would be nice if you would start with branch #sii-irq when you 
>> are updating the sata_sil interrupt handling path.
> 
> I certainly can, but I'm not sure it's a good idea to do it.  Most 
> likely, it will end up in another rewriting of the rewritten irq handler 
> (commit-wise, it will be merge-sii-irq then rewrite sii-irq).  The new 
> one in hp-LLDD-prep uses BMDMA2 to cut down on IO access and also makes 
> use of the fact that sata_sil uses ATA_DMA_INTR bit to indicate IRQ 
> pending even when non-DMA command is in progress, so the whole structure 
> is somewhat different from the one in sii-irq.

OK.  I'll drop my branch then.


>  > And eventually we want to push #sii-lbt too.
> 
> Yeap, I looked at that one, too.  But, IIRC, the test result wasn't too 
> positive.  Am I remembering correctly?

My test results were quite positive :)  At least one negative report on 
3114 IIRC.

	Jeff