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
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