Re: [ALSA patch] [PATCH] ALSA: pcm: Enable MMAP status and control for ARMv7 and ARMv8

[Timo Wischer]

On 4/17/19 11:21, Takashi Iwai wrote:
> On Wed, 17 Apr 2019 10:46:11 +0200,
> <twischer@xxxxxxxxxxxxxx> wrote:
> > From: Timo Wischer <twischer@xxxxxxxxxxxxxx>
> >
> > Since ARMv7 hardware cache coherence is supported.
> > "The SCU maintains coherency between the individual data caches in the
> > Cortex-A5 MPCore processor using a variation of the MOESI protocol" [1].
> >
> > Therefore this patch enables the MMAP access to the status and control
> > structures. This avoids HWSYYNC ioctl calls and therefore lowers the CPU
> > usage.
> >
> > [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0434c/
> > BABJECBF.html
> Interesting...  I thought it would never work properly on ARM.
> If it really works like that, I'd happily apply the change.
> But I'd like to hear a confirmation from ARM people before merging
> such an intensive change.

Hi Takashi,

do I need to send this patch to any other mailing list or do you think 
some corresponding guy is already on the lists I have used?

> thanks,
>
> Takashi
>
> > Signed-off-by: Timo Wischer <twischer@xxxxxxxxxxxxxx>
> > ---
> >   sound/core/pcm_native.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> > index 1d84529..b8019ef 100644
> > --- a/sound/core/pcm_native.c
> > +++ b/sound/core/pcm_native.c
> > @@ -3225,7 +3225,8 @@ static __poll_t snd_pcm_poll(struct file *file, poll_table *wait)
> >    * Only on coherent architectures, we can mmap the status and the control records
> >    * for effcient data transfer.  On others, we have to use HWSYNC ioctl...
> >    */
> > -#if defined(CONFIG_X86) || defined(CONFIG_PPC) || defined(CONFIG_ALPHA)
> > +#if defined(CONFIG_X86) || defined(CONFIG_PPC) || defined(CONFIG_ALPHA) || \
> > +	(defined(CONFIG_ARM) && defined(CONFIG_CPU_V7)) || defined(CONFIG_ARM64)
> >   /*
> >    * mmap status record
> >    */
> > --
> > 2.7.4
> >
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