linux-kernel - Re: [PATCH v2 27/27] sound: ppc: remove unneeded memset after dma_alloc

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Date:   Fri, 28 Jun 2019 17:11:08 +0800
From:   Fuqian Huang <huangfq.daxian@...il.com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Rob Herring <robh@...nel.org>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Richard Fontana <rfontana@...hat.com>,
        Paul Mackerras <paulus@...ba.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linuxppc-dev@...ts.ozlabs.org, Allison Randal <allison@...utok.net>
Subject: Re: [PATCH v2 27/27] sound: ppc: remove unneeded memset after dma_alloc_coherent

The merge commit log tells (dma-mapping: zero memory returned from
dma_alloc_* and deprecating the dma_zalloc_coherent).
I used this commit just want to say that dma_alloc_coherent  has
zeroed the allocated memory.
Sorry for this mistake.

Maybe this commit 518a2f1925c3("dma-mapping: zero memory returned from
dma_alloc_*") is correct.

Christophe Leroy <christophe.leroy@....fr> 於 2019年6月28日週五 下午4:59寫道：

>
>
>
> Le 28/06/2019 à 04:50, Fuqian Huang a écrit :
> > In commit af7ddd8a627c
> > ("Merge tag 'dma-mapping-4.21' of git://git.infradead.org/users/hch/dma-mapping"),
> > dma_alloc_coherent has already zeroed the memory.
> > So memset is not needed.
>
> You are refering to a merge commit, is that correct ?
>
> I can't see anything related in that commit, can you please pinpoint it ?
>
> As far as I can see, on powerpc the memory has always been zeroized
> (since 2005 at least).
>
> Christophe
>
> >
> > Signed-off-by: Fuqian Huang <huangfq.daxian@...il.com>
> > ---
> >   sound/ppc/pmac.c | 1 -
> >   1 file changed, 1 deletion(-)
> >
> > diff --git a/sound/ppc/pmac.c b/sound/ppc/pmac.c
> > index 1b11e53f6a62..1ab12f4f8631 100644
> > --- a/sound/ppc/pmac.c
> > +++ b/sound/ppc/pmac.c
> > @@ -56,7 +56,6 @@ static int snd_pmac_dbdma_alloc(struct snd_pmac *chip, struct pmac_dbdma *rec, i
> >       if (rec->space == NULL)
> >               return -ENOMEM;
> >       rec->size = size;
> > -     memset(rec->space, 0, rsize);
> >       rec->cmds = (void __iomem *)DBDMA_ALIGN(rec->space);
> >       rec->addr = rec->dma_base + (unsigned long)((char *)rec->cmds - (char *)rec->space);
> >
> >