Re: [PATCH v7 01/33] xhci: add support to allocate several interrupters

[Mathias Nyman]

On 2.10.2023 23.07, Wesley Cheng wrote:
> Hi Mathias,
>
> On 9/28/2023 3:31 AM, Mathias Nyman wrote:
> > On 22.9.2023 0.48, Wesley Cheng wrote:
> > > From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
> > >
> > > Modify the XHCI drivers to accommodate for handling multiple event rings in
> > > case there are multiple interrupters.  Add the required APIs so clients are
> > > able to allocate/request for an interrupter ring, and pass this information
> > > back to the client driver.  This allows for users to handle the resource
> > > accordingly, such as passing the event ring base address to an audio DSP.
> > > There is no actual support for multiple MSI/MSI-X vectors.
> > >
> > > Factoring out XHCI interrupter APIs and structures done by Wesley Cheng, in
> > > order to allow for USB class drivers to utilze them.
> > >
> > >   }
> > > +void xhci_remove_secondary_interrupter(struct usb_hcd *hcd, struct xhci_interrupter *ir)
> > > +{
> > > +    struct xhci_hcd *xhci = hcd_to_xhci(hcd);
> > > +    unsigned int intr_num;
> > > +
> > > +    /* interrupter 0 is primary interrupter, don't touchit */
> > > +    if (!ir || !ir->intr_num || ir->intr_num >= xhci->max_interrupters) {
> > > +        xhci_dbg(xhci, "Invalid secondary interrupter, can't remove\n");
> > > +        return;
> > > +    }
> > > +
> > > +    /* fixme, should we check xhci->interrupter[intr_num] == ir */
> > > +    spin_lock(&xhci->lock);
> >
> > Needs to be spin_lock_irq() ir spin_lock_irqsave() as xhci->lock is used in interrupt handler.
> >
> >
> > > +    intr_num = ir->intr_num;
> > > +    xhci_free_interrupter(xhci, ir);
> > > +    xhci->interrupters[intr_num] = NULL;
> > > +    spin_unlock(&xhci->lock);
> >
> > likewise
>
> Let me check these again.  In general, I think I will use both the xhci->mutex and 
> xhci->lock where needed, because I believe we'd run into sleep while atomic issues
> while freeing the DMA memory.  Will rework this and submit in the next rev.

Maybe we need to split xhci_free_interrupter() into separate remove and free functions

Did some work on this, and on the sideband api in general.

Code still has a lot of FIXMEs, and it's completely untested, but to avoid us
from doing duplicate work I pushed it to my feature_interrupters branch anyway

git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git feature_interrupters
https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=feature_interrupters

Thanks
-Mathias