Hi Adrian,
On 22/03/21 8:27 pm, John Paul Adrian Glaubitz wrote:
Hi Michael!
On 3/22/21 3:31 AM, Michael Schmitz wrote:
note that the libata driver for Falcon does not utilize interrupts due to the
interaction between IDE, SCSI and floppy hardware, the latter two also making
use of the ST-DMA chip which cannot be transparently checked for DMA completion.
Instead, the libata driver polls for IDE command completion. This may add a
little
latency, but that's probably offset by the lack of contention between IDE and
SCSI
drivers in mixed IDE / SCSI operation. In my tests, I haven't found any
substantial
impact from the driver change (and I was quite sceptical of the libata driver
performance).
Is this a fundamental limitation of libata that interrupts are not supported or
just
a limitation of pata_falcon?
Only affects pata_falcon, and this was a design decision of the libata
authors to not copy the clunky code that guards against simultaneous use
of IDE and SCSI/floppy on Falcon.
No other IDE hardware supported by libata appears to require such
locking. I'm sure it could be added back, but I won't open that
particular can of worms.
Cheers,
Michael
Adrian
