On Fri, Sep 19, 2014 at 09:34:34AM -0700, Dan Williams wrote:
> On Fri, Sep 19, 2014 at 1:25 AM, Alexander Gordeev <agordeev@xxxxxxxxxx> wrote:
> > As described in AHCI v1.0 specification chapter 10.6.2.2
> > "Multiple MSI Based Messages" generation of interrupts
> > is not controlled through the HOST_IRQ_STAT register.
> >
> > Considering MMIO access is expensive remove unnecessary
> > reading and writing of HOST_IRQ_STAT register.
> >
> > Further, serializing access to the host data is no longer
> > needed and the interrupt service routine can avoid competing
> > on the host lock.
> >
> > Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>
> > Suggested-by: "Jiang, Dave" <dave.jiang@xxxxxxxxx>
> > Cc: linux-ide@xxxxxxxxxxxxxxx
> > ---
> > drivers/ata/ahci.h | 1 +
> > drivers/ata/libahci.c | 54 ++++++++-------------------------------------------
> > 2 files changed, 9 insertions(+), 46 deletions(-)
> >
> > diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
> > index c12f590..b8e117a 100644
> > --- a/drivers/ata/ahci.h
> > +++ b/drivers/ata/ahci.h
> > @@ -305,6 +305,7 @@ struct ahci_port_priv {
> > unsigned int ncq_saw_dmas:1;
> > unsigned int ncq_saw_sdb:1;
> > u32 intr_status; /* interrupts to handle */
> > + spinlock_t intr_lock; /* protects intr_status */
>
> Why introduce a new lock? Can't we switch to per-ata port locking
> rather than ata_host locking?
We could. But this case hardware context interrupt handler would compete
with threads/softriqs, which is exactly what I tried to avoid. With the
separate lock we *only* update ahci_port_priv::intr_status with interrupts
disabled.
--
Regards,
Alexander Gordeev
agordeev@xxxxxxxxxx
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