Messages in this thread | | | From | Anup Patel <> | Date | Sat, 26 Nov 2022 21:30:31 +0530 | Subject | Re: [PATCH v11 3/7] genirq: Add mechanism to multiplex a single HW IPI |
| |
On Sat, Nov 26, 2022 at 7:58 PM Marc Zyngier <maz@kernel.org> wrote: > > On Sat, 26 Nov 2022 13:31:46 +0000, > Anup Patel <apatel@ventanamicro.com> wrote: > > > > On Sat, Nov 26, 2022 at 6:12 PM Marc Zyngier <maz@kernel.org> wrote: > > > > > > On Mon, 14 Nov 2022 09:39:00 +0000, > > > Anup Patel <apatel@ventanamicro.com> wrote: > > > > > > > > +struct ipi_mux_control { > > > > + void *data; > > > > + unsigned int nr; > > > > > > Honestly, I think we can get rid of this. The number of IPIs Linux > > > uses is pretty small, and assuming a huge value (like 32) would be > > > enough. It would save looking up this value on each IPI handling. > > > > I had kept in-case some driver wanted to create fewer (< 32) > > muxed IPIs. > > I'm fine with being able to specifying the max, but I'm not sure there > is a need to keep track of it any further. Certainly, the overhead of > loading this value on each IPI could be removed. On most architecture, > for_each_set_bit() and co and better optimised with a fixed number of > bits.
Okay, I will update like you suggested.
> > > > > +static const struct irq_chip ipi_mux_chip = { > > > > + .name = "IPI Mux", > > > > + .irq_mask = ipi_mux_mask, > > > > + .irq_unmask = ipi_mux_unmask, > > > > + .ipi_send_mask = ipi_mux_send_mask, > > > > +}; > > > > > > I really think this could either be supplied by the irqchip, or > > > somehow patched to avoid the pointless imux->ops->ipi_mux_send > > > indirection. Pointer chasing hurts. > > > > Once we remove ipi_mux_pre/post_handle() callbacks, the > > "ops" will be pointless and we will be able to remove one level > > of indirection here. > > > > We certainly need a mux irqchip to implement the > > mask/unmask semantics for muxed IPIs. > > I'm not disputing that last point. > > > > > +/** > > > > + * ipi_mux_create - Create virtual IPIs multiplexed on top of a single > > > > + * parent IPI. > > > > + * @parent_virq: virq of the parent per-CPU IRQ > > > > + * @nr_ipi: number of virtual IPIs to create. This should > > > > + * be <= BITS_PER_TYPE(int) > > > > + * @ops: multiplexing operations for the parent IPI > > > > + * @data: opaque data used by the multiplexing operations > > > > > > What is the use for data? If anything, that data should be passed via > > > the mux interrupt. But the whole point of this is to make the mux > > > invisible. So this whole 'data' business is a mystery to me. > > > > This is added only to pass back driver data in ipi_mux_send(). > > Again, what is the purpose of such data? If you need per-interrupt > data, this should be provided by the requester of the interrupt.
Currently, the irqchip drivers that we care about don't need this data pointer so I will remove it. If required we can add it in future.
> > M. > > -- > Without deviation from the norm, progress is not possible.
Thanks, Anup
| |