From: Lars-Peter Clausen <lars@metafoo.de>
To: Takashi Iwai <tiwai@suse.de>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
Stephen Warren <swarren@nvidia.com>,
Mark Brown <broonie@opensource.wolfsonmicro.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Laxman Dewangan <ldewangan@nvidia.com>, "lrg@ti.com" <lrg@ti.com>,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH] ASoC: snd_dmaengine: add common api for pcm_mmap
Date: Fri, 29 Jun 2012 18:42:23 +0200 [thread overview]
Message-ID: <4FEDDAEF.5020609@metafoo.de> (raw)
In-Reply-To: <s5hd34jzgs0.wl%tiwai@suse.de>
On 06/28/2012 03:51 PM, Takashi Iwai wrote:
> At Thu, 28 Jun 2012 19:06:07 +0530,
> Laxman Dewangan wrote:
> [...]
>
> But, still we need to be careful about this. As mentioned, there is
> no flag to know the possibility of writecombine mmap beforehand.
> It'd be nice if we have either a compile-time or a run-time flag /
> function to check that. Then the driver can also expose the mmap
> capability to user-space depending on the flag.
>
If writecombine is not supported it will fallback to a "normal" mmap.
Here's an excerpt from the DMA mapping documentation:
DMA_ATTR_WRITE_COMBINE
----------------------
DMA_ATTR_WRITE_COMBINE specifies that writes to the mapping may be
buffered to improve performance.
Since it is optional for platforms to implement DMA_ATTR_WRITE_COMBINE,
those that do not will simply ignore the attribute and exhibit default
behavior.
- Lars
WARNING: multiple messages have this Message-ID (diff)
From: Lars-Peter Clausen <lars@metafoo.de>
To: Takashi Iwai <tiwai@suse.de>
Cc: Laxman Dewangan <ldewangan@nvidia.com>,
"alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
Stephen Warren <swarren@nvidia.com>,
Mark Brown <broonie@opensource.wolfsonmicro.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"lrg@ti.com" <lrg@ti.com>,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [alsa-devel] [PATCH] ASoC: snd_dmaengine: add common api for pcm_mmap
Date: Fri, 29 Jun 2012 18:42:23 +0200 [thread overview]
Message-ID: <4FEDDAEF.5020609@metafoo.de> (raw)
In-Reply-To: <s5hd34jzgs0.wl%tiwai@suse.de>
On 06/28/2012 03:51 PM, Takashi Iwai wrote:
> At Thu, 28 Jun 2012 19:06:07 +0530,
> Laxman Dewangan wrote:
> [...]
>
> But, still we need to be careful about this. As mentioned, there is
> no flag to know the possibility of writecombine mmap beforehand.
> It'd be nice if we have either a compile-time or a run-time flag /
> function to check that. Then the driver can also expose the mmap
> capability to user-space depending on the flag.
>
If writecombine is not supported it will fallback to a "normal" mmap.
Here's an excerpt from the DMA mapping documentation:
DMA_ATTR_WRITE_COMBINE
----------------------
DMA_ATTR_WRITE_COMBINE specifies that writes to the mapping may be
buffered to improve performance.
Since it is optional for platforms to implement DMA_ATTR_WRITE_COMBINE,
those that do not will simply ignore the attribute and exhibit default
behavior.
- Lars
next prev parent reply other threads:[~2012-06-29 16:38 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-28 7:01 [PATCH] ASoC: snd_dmaengine: add common api for pcm_mmap Laxman Dewangan
2012-06-28 7:01 ` Laxman Dewangan
2012-06-28 10:51 ` Mark Brown
2012-06-28 10:51 ` Mark Brown
2012-06-28 11:56 ` Laxman Dewangan
2012-06-28 12:02 ` Mark Brown
2012-06-28 12:07 ` Laxman Dewangan
2012-06-28 12:44 ` Lars-Peter Clausen
2012-06-28 14:03 ` Takashi Iwai
2012-06-28 14:03 ` [alsa-devel] " Takashi Iwai
2012-06-28 11:09 ` Lars-Peter Clausen
2012-06-28 11:09 ` Lars-Peter Clausen
2012-06-28 12:15 ` Takashi Iwai
2012-06-28 12:18 ` Mark Brown
2012-06-28 12:18 ` [alsa-devel] " Mark Brown
2012-06-28 12:30 ` Lars-Peter Clausen
2012-06-28 12:30 ` [alsa-devel] " Lars-Peter Clausen
2012-06-28 12:28 ` Mark Brown
2012-06-28 12:35 ` Laxman Dewangan
2012-06-28 12:57 ` Takashi Iwai
2012-06-28 12:57 ` [alsa-devel] " Takashi Iwai
2012-06-28 13:04 ` Laxman Dewangan
2012-06-28 13:28 ` Takashi Iwai
2012-06-28 13:28 ` [alsa-devel] " Takashi Iwai
2012-06-28 13:36 ` Laxman Dewangan
2012-06-28 13:51 ` Takashi Iwai
2012-06-28 14:00 ` Laxman Dewangan
2012-06-28 14:10 ` Takashi Iwai
2012-06-29 16:42 ` Lars-Peter Clausen [this message]
2012-06-29 16:42 ` Lars-Peter Clausen
2012-07-02 12:50 ` Marek Szyprowski
2012-06-28 12:32 ` Clemens Ladisch
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