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From: Grant Likely <grant.likely@secretlab.ca>
Date: Mon, 25 May 2009 10:00:57 -0600
Message-ID: <fa686aa40905250900g25ad3e34q7535a8ebb1197962@mail.gmail.com>
Subject: Re: [PATCH V3 2/4] AC97 driver for mpc5200
To: Jon Smirl <jonsmirl@gmail.com>
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Cc: linuxppc-dev@ozlabs.org, alsa-devel@alsa-project.org,
	Mark Brown <broonie@opensource.wolfsonmicro.com>
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On Mon, May 25, 2009 at 9:21 AM, Jon Smirl <jonsmirl@gmail.com> wrote:
> On Mon, May 25, 2009 at 6:26 AM, Mark Brown
> <broonie@opensource.wolfsonmicro.com> wrote:
>>> + =A0 =A0 =A0 =A0 =A0 =A0 spin_lock(&psc_dma->lock);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 out_be32(&psc_dma->psc_regs->ac97_slots, psc_=
dma->slots);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 spin_unlock(&psc_dma->lock);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 break;
>>
>> This locking looks wrong - I'd expect it to also cover the modification
>> of psc_dma->slots? =A0Otherwise it's hard to see what it buys you.
>
> Grant, why are you spin locking around register access?

This lock/unlock is definitely bogus since a single register access is
already atomic.  Are there places in the code that I wrote where a
spin_lock/unlock is done around a single register access?

g.

--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.