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SubjectRe: [PATCH] nvme: Add support for Apple 2018+ models
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On Mon, 2019-07-15 at 10:10 +0200, Christoph Hellwig wrote:
> > + /*
> > + * Apple 2018 and latter variant has a few issues
> > + */
> > + NVME_QUIRK_APPLE_2018 = (1 << 10),
>
> We try to have quirks for the actual issue, so this should be one quirk
> for the irq vectors issues, and another for the sq entry size. Note that
> NVMe actually has the concept of an I/O queue entry size (IOSQES in the
> Cc register based on values reported in the SQES field in Identify
> Controller. Do these controllers report anything interesting there?

Ah good to know, I'll dig.

> At the very least I'd make all the terminology based on that and then
> just treat the Apple controllers as a buggy implementation of that model.

Yup, sounds good. I'll poke around tomorrow.

> Btw, are there open source darwin NVMe driver that could explain this
> mess a little better?

You wish...

> > @@ -504,8 +505,11 @@ static inline void nvme_write_sq_db(struct nvme_queue *nvmeq, bool write_sq)
> > static void nvme_submit_cmd(struct nvme_queue *nvmeq, struct nvme_command *cmd,
> > bool write_sq)
> > {
> > + u16 sq_actual_pos;
> > +
> > spin_lock(&nvmeq->sq_lock);
> > - memcpy(&nvmeq->sq_cmds[nvmeq->sq_tail], cmd, sizeof(*cmd));
> > + sq_actual_pos = nvmeq->sq_tail << nvmeq->sq_extra_shift;
> > + memcpy(&nvmeq->sq_cmds[sq_actual_pos], cmd, sizeof(*cmd));
>
> This is a little too magic. I think we'd better off making sq_cmds
> a void array and use manual indexing, at least that makes it very
> obvious what is going on.

Ok. That's plan B as I described in the message. There's an advantage
to do that, it merges the indexing shift and the quirk shift into one.

I'll look into it & respin

> > - nvmeq->sq_cmds, SQ_SIZE(nvmeq->q_depth));
> > + nvmeq->sq_cmds, SQ_SIZE(nvmeq));
>
> Btw, chaning SQ_SIZE to take the queue seems like something that should
> be split into a prep patch, making the main change a lot smaller.

Sure. Will do.

> > - if (!polled)
> > + if (!polled) {
> > +
> > + /*
> > + * On Apple 2018 or later implementations, only vector 0 is accepted
>
> Please fix the > 80 char line.

Ok.

Thanks for the review.

Cheers,
Ben.


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