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    SubjectRe: [ALSA patch] [PATCH] ALSA: pcm: Enable MMAP status and control for ARMv7 and ARMv8
    On Wed, 17 Apr 2019 11:30:10 +0200,
    Timo Wischer wrote:
    >
    > On 4/17/19 11:21, Takashi Iwai wrote:
    > > 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.
    >
    > 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?

    Well, maybe we need to ping ARM people if no one on the lists you
    Cc'ed give comments. Let's see.


    Takashi

    >
    > >
    > >
    > > 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
    > >>
    >

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