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

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Date:   Wed, 3 Jul 2019 23:45:37 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     Andrey Smirnov <andrew.smirnov@...il.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 7/3/2019 8:14 PM, Andrey Smirnov wrote:
> 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.

I took a second look at caam_jr_init and there is apparently a whole 
bunch of other reset/init stuff done after request_irq. For example 
caam_reset_hw_jr is done after request_irq and masks interrupts?

What I'd expect is that request_irq is done last after all other 
initialization is performed. But I'm not familiar with how CAAM JRs work 
so feel free to ignore this.

--
Regards,
Leonard