Re: [PATCH/RFC 3/5] libata-dev: Let ata_hsm_move() work with both irq-pio and polling pio

[Tejun Heo <htejun@gmail.com>]

Albert Lee wrote:
> Tejun Heo wrote:
>>
>>For ATA PIO write transfers, the first transfer and n'th transfers
>>aren't really different.  The code would be simpler if it handles the
>>first ATA PIO write in HSM_ST.  And if we do that, HSM_ST_FIRST can be
>>renamed to HSM_ST_CDB.  Hmmm.. Maybe this should be done in separate
>>series of patches.
>>
> 
> 
> For ATA PIO write transfer, the first transfer is different:
> It is always done by polling, even if irq is turned on.
> 
> If we treat the first PIO write transfer as HSM_ST, we need to add some
> additional logic to HSM_ST and check whether it is first transfer or not. If it is,
> and irq is on, the transition from polling to interrupt-driven must be protected
> by spinlock, similar to what's done in HSM_ST_FIRST.

Oh, you're right. I wasn't thinking of the spinlock. I implemented HSM 
for sata_sil vdma (still slightly broken) and made its HSM function 
always called under the host spinlock, so I could merge ATA HSM_ST_FIRST 
into HSM_ST for ATA WRITE's and got confused about your HSM.  :-)

Hmmm.. I'm not sure but I recall to read about IDE controllers reacting 
badly when disturbed during PIO thus requiring irq-off during PIO. Does 
anyone know better about this?

-- 
tejun