>>> On 10.04.13 at 17:42, Alexander Gordeev <agordeev@xxxxxxxxxx> wrote: > On Wed, Apr 10, 2013 at 04:05:30PM +0100, Jan Beulich wrote: >> Alexander, >> >> I'm a bit puzzled by the way ahci_init_interrupts() works, when >> looking at a particular hardware implementation having 6 ports >> but allowing up to 16 MSIs - obviously, with one IRQ per port, >> obtaining 8 MSIs would be sufficient in this case, conserving on >> resources. Is there any reason this can't be done (i.e. by the >> caller of pci_enable_msi_block_auto() passing in the maximum >> desired number)? > > There are few points here. > > 1. Some (all?) hardware implementations (i.e. Intel) have stupid > logic that falls back to single MSI mode as if MRSM bit was set, > in case # of allocated MSIs is less than # of available MSIs, > even though # of allocated MSIs >= # of ports. I did not find any > chips which could perform otherwise and stuck with this simpler > mode for now. > > 2. I did implement the approach you described - you can look at it > in my earlier versions of the patchset. But I withdrew the change, > since an update to the generic MSI code was needed, and it would be > hard to convince people to accept changes that nobody consumes. > > 3. If you aware of any hardware that is able sending multiple MSIs > while the condition holds true: > # of ports <= # of allocated MSIs < # of available MSIs > ...I can revive my changes and post it upstream. I'll have to see if I can check the two or three capable machines I have, but considering what you describe I'm sure the same will apply there. Thanks for explaining! >> Besides that, would it be possible to tweak things so that >> /proc/interrupts could show distinct names for the individual >> IRQs? > > I am not sure what do you mean here. Once a separate MSI vector is > allocated to a port (to anything in fact) it will show up in > /proc/interrupts as a distinct record. They have separate lines, but all say just "ahci" at the end (as opposed to e.g. all the USB consumed ones, which are nicely distinguishable). Jan -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
