linux-kernel - Re: [PATCH v4 03/16] crypto: caam

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Message-ID: <CAHQ1cqHfBU92g-P7jDfiWtEr0m-kv5Lw9yZcvUEXYg7OyhURfg@mail.gmail.com>
Date:   Wed, 3 Jul 2019 10:14:38 -0700
From:   Andrey Smirnov <andrew.smirnov@...il.com>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Horia Geanta <horia.geanta@....com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Chris Spencer <christopher.spencer@....co.uk>,
        Cory Tusar <cory.tusar@....aero>,
        Chris Healy <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Aymen Sghaier <aymen.sghaier@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 03/16] crypto: caam - move tasklet_init() call down

On Wed, Jul 3, 2019 at 6:51 AM Leonard Crestez <leonard.crestez@....com> wrote:
>
> On 7/3/2019 11:14 AM, Andrey Smirnov wrote:
> > Move tasklet_init() call further down in order to simplify error path
> > cleanup. No functional change intended.
> >
> > diff --git a/drivers/crypto/caam/jr.c b/drivers/crypto/caam/jr.c
> > index 4b25b2fa3d02..a7ca2bbe243f 100644
> > --- a/drivers/crypto/caam/jr.c
> > +++ b/drivers/crypto/caam/jr.c
> > @@ -441,15 +441,13 @@ static int caam_jr_init(struct device *dev)
> >
> >       jrp = dev_get_drvdata(dev);
> >
> > -     tasklet_init(&jrp->irqtask, caam_jr_dequeue, (unsigned long)dev);
> > -
> >       /* Connect job ring interrupt handler. */
> >       error = request_irq(jrp->irq, caam_jr_interrupt, IRQF_SHARED,
> >                           dev_name(dev), dev);
> >       if (error) {
> >               dev_err(dev, "can't connect JobR %d interrupt (%d)\n",
> >                       jrp->ridx, jrp->irq);
> > -             goto out_kill_deq;
> > +             return error;
> >       }
>
> The caam_jr_interrupt handler can schedule the tasklet so it makes sense
> to have it be initialized ahead of request_irq. In theory it's possible
> for an interrupt to be triggered immediately when request_irq is called.
>
> I'm not very familiar with the CAAM ip, can you ensure no interrupts are
> pending in HW at probe time? The "no functional change" part is not obvious.
>

Said tasklet will use both jrp->outring and jrp->entinfo array
initialized after IRQ request call in both versions of the code
(before/after this patch). AFAICT, the only case where this patch
would change initialization safety of the original code is if JR was
scheduled somehow while ORSFx is 0 (no jobs done), which I don't think
is possible.

Thanks,
Andrey Smirnov