Hello, Robert.
On Mon, May 11, 2015 at 07:18:10PM +0200, Robert Richter wrote:
> static int ahci_init_msix(struct pci_dev *pdev, unsigned int n_ports,
> struct ahci_host_priv *hpriv)
> {
> int rc, nvec;
> struct msix_entry entry = {};
>
> /* check if msix is supported */
> nvec = pci_msix_vec_count(pdev);
> if (nvec <= 0)
> return 0;
>
> /*
> * Per-port msix interrupts are not supported. Assume single
> * port interrupts for:
> *
> * n_ports == 1, or
> * nvec < n_ports.
> *
> * We also need to check for n_ports != 0 which is implicitly
> * covered here since nvec > 0.
> */
> if (n_ports != 1 && nvec >= n_ports)
> return -ENOSYS;
Why are failing the whole thing when nvec >= n_ports? Can't we just
print some warning and configure it for single interrupt mode?
> > Also, shouldn't we be printing a warning message here explaining why
> > probing is failing?
>
> I didn't want to print a warning in case -ENOSYS for backward
> compatability. Only if msi-x code fails there is a message, see
> __ahci_init_interrupts(). In any other case the behaviour is as
> before, thus no message is printed.
I'm confused here. Why are we implementing msix support at all if it
only support single interrupt mode? I kinda assumed that that was
because you're trying to support a controller which does only msix,
no? At any rate, I don't think it's wrong to print an informational /
warning message when a controller declares msix support but has wacko
parameters.
> > > +
> > > + /* only enable the first entry (entry.entry = 0) */
> > > + rc = pci_enable_msix_exact(pdev, &entry, 1);
> >
> > So, enabling the first msix works if nvec > 1 && nvec < n_ports but
> > not if nvec >= n_ports?
>
> For n_ports > 1 && nvec >= n_ports we need to assume per-port
> interrupts. There are enough vectors for all ports then.
Again, and we fail irq init in that case?
Thanks.
--
tejun
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