lkml.org 
[lkml]   [2019]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [ALSA patch] [PATCH] ALSA: pcm: Enable MMAP status and control for ARMv7 and ARMv8
On Wed, 17 Apr 2019 10:46:11 +0200,
<twischer@de.adit-jv.com> wrote:
>
> From: Timo Wischer <twischer@de.adit-jv.com>
>
> 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.


thanks,

Takashi

>
> Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>
> ---
> 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
>
> _______________________________________________
> Patch mailing list
> Patch@alsa-project.org
> https://mailman.alsa-project.org/mailman/listinfo/patch
>

\
 
 \ /
  Last update: 2019-04-17 11:23    [W:0.075 / U:3.112 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site