Hi,
On Wed, Jun 30, 2021, at 15:49, Alyssa Rosenzweig wrote:
> Looks really good! Just a few minor comments. With them addressed,
>
> Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@xxxxxxxxxxxxx>
Thanks!
>
> > + Say Y here if you are using an Apple SoC with a DART IOMMU.
>
> Nit: Do we need to spell out "with a DART IOMMU"? Don't all the apple
> socs need DART?
Good point, I'll remove it.
>
> > +/*
> > + * This structure is used to identify a single stream attached to a domain.
> > + * It's used as a list inside that domain to be able to attach multiple
> > + * streams to a single domain. Since multiple devices can use a single stream
> > + * it additionally keeps track of how many devices are represented by this
> > + * stream. Once that number reaches zero it is detached from the IOMMU domain
> > + * and all translations from this stream are disabled.
> > + *
> > + * @dart: DART instance to which this stream belongs
> > + * @sid: stream id within the DART instance
> > + * @num_devices: count of devices attached to this stream
> > + * @stream_head: list head for the next stream
> > + */
> > +struct apple_dart_stream {
> > + struct apple_dart *dart;
> > + u32 sid;
> > +
> > + u32 num_devices;
> > +
> > + struct list_head stream_head;
> > +};
>
> It wasn't obvious to me why we can get away without reference counting.
> Looking ahead it looks like we assert locks in each case. Maybe add
> that to the comment?
Sure, I'll add that to the comment.
>
> ```
> > +static void apple_dart_hw_set_ttbr(struct apple_dart *dart, u16 sid, u16 idx,
> > + phys_addr_t paddr)
> > +{
> > + writel(DART_TTBR_VALID | (paddr >> DART_TTBR_SHIFT),
> > + dart->regs + DART_TTBR(sid, idx));
> > +}
> ```
>
> Should we be checking alignment here? Something like
>
> BUG_ON(paddr & ((1 << DART_TTBR_SHIFT) - 1));
>
Sure, right now paddr will always be aligned but adding that
BUG_ON doesn't hurt :)
Best,
Sven
