memory allocate for substream->runtime->dma_area

memory allocate for substream->runtime->dma_area

[boku]

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Dear all,
    Could anyone tell me where the memory allocation of substream->runtime
is? I got to refine the runtime->dma_area within a specific DMA address. But
I can't find where the dma alloc is. Thanks a lot!

BR,

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memory allocate for substream->runtime->dma_area

[boku]

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 Dear all,
    Could anyone tell me where the memory allocation of substream->runtime
is? I got to refine the runtime->dma_area within a specific DMA address. But
I can't find where the dma alloc is. Thanks a lot!

BR,

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Re: memory allocate for substream->runtime->dma_area

[Lee Revell]

On Wed, 2006-03-15 at 11:43 +0800, boku wrote:
> Dear all,
>     Could anyone tell me where the memory allocation of
> substream->runtime is? I got to refine the runtime->dma_area within a
> specific DMA address. But I can't find where the dma alloc is. Thanks
> a lot! 

This question is pretty cryptic, can you describe what you are trying to
do and post a link to your code?  Did you read the ALSA driver guide?

Lee



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Re: memory allocate for substream->runtime->dma_area

[Takashi Iwai]

At Wed, 15 Mar 2006 11:43:51 +0800,
boku wrote:
> 
> Dear all,
>     Could anyone tell me where the memory allocation of substream->runtime is? I got
> to refine the runtime->dma_area within a specific DMA address. But I can't find where
> the dma alloc is. Thanks a lot!

The driver has to allocate the DMA buffer by itself.

Most drivers use the helper functions, snd_pcm_lib_preallocate_*() at
creation and snd_pcm_lib_malloc_pages() at hw_params callback, so that
the PCM middle layer takes over the jobs.  But, in special cases, you
need to allocate the buffer or assign the fixed addresses by
yourself.

Anyway, better to show your code and read the documentation once, as
Lee suggested.


Takashi


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Fwd: memory allocate for substream->runtime->dma_area

[boku]

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 Dear all,
     Could you please tell me what the "frame" and "period" mean in alsa?
I saw snd_pcm_hardware_t struct has period_min,max, period_bytes_min,max etc
but quite confused of their meaning. So is the fifo size.
    And btw, which data struct has the info of how many bits per channel for
the wav bitstream from alsa application aplay etc? Such as 16-bits, 24 or
32-bits.
Thanks for your great help~


 On 3/16/06, Lee Revell <rlrevell@joe-job.com > wrote:
>
> On Wed, 2006-03-15 at 12:03 +0800, boku wrote:
> > Hi, Lee,
> >      Thanks for quick response. Currently I'm designing the sound
> > driver for an ARM integrator/ap-like platform. But in the platform,
> > the audio controller is designated to move data only from a specific
> > address space. Therefore, doesn't it mean that i need to constrain the
> > runtime->dma_area to the specified address so that the AIC can start
> > to do DMA access?
> > Sorry about the code still not done and thanks in advance.
>
> Sorry I'm not really an ARM expert, but this has come up in the list
> archive before.  You should look at some of the other ARM drivers in the
> tree...
>
> Lee
>
>
>

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Re: memory allocate for substream->runtime->dma_area

[boku]

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Is there any example case that uses fixed address space for the DMA region?
Thanks!~


On 3/15/06, Takashi Iwai <tiwai@suse.de> wrote:
>
> At Wed, 15 Mar 2006 11:43:51 +0800,
> boku wrote:
> >
> > Dear all,
> >     Could anyone tell me where the memory allocation of
> substream->runtime is? I got
> > to refine the runtime->dma_area within a specific DMA address. But I
> can't find where
> > the dma alloc is. Thanks a lot!
>
> The driver has to allocate the DMA buffer by itself.
>
> Most drivers use the helper functions, snd_pcm_lib_preallocate_*() at
> creation and snd_pcm_lib_malloc_pages() at hw_params callback, so that
> the PCM middle layer takes over the jobs.  But, in special cases, you
> need to allocate the buffer or assign the fixed addresses by
> yourself.
>
> Anyway, better to show your code and read the documentation once, as
> Lee suggested.
>
>
> Takashi
>

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Re: Fwd: memory allocate for substream->runtime->dma_area

[Carlos Munoz]

boku wrote:

>
> Dear all,
>     Could you please tell me what the "frame" and "period" mean in alsa?
> I saw snd_pcm_hardware_t struct has period_min,max, 
> period_bytes_min,max etc but quite confused of their meaning. So is 
> the fifo size.
>     And btw, which data struct has the info of how many bits per 
> channel for the wav bitstream from alsa application aplay etc? Such as 
> 16-bits, 24 or 32-bits.
> Thanks for your great help~
>  
>  
> On 3/16/06, *Lee Revell* <rlrevell@joe-job.com 
> <mailto:rlrevell@joe-job.com> > wrote:
>
>     On Wed, 2006-03-15 at 12:03 +0800, boku wrote:
>> Hi, Lee,
>>      Thanks for quick response. Currently I'm designing the sound
>> driver for an ARM integrator/ap-like platform. But in the platform,
>> the audio controller is designated to move data only from a specific
>> address space. Therefore, doesn't it mean that i need to
>     constrain the
>> runtime->dma_area to the specified address so that the AIC can start
>> to do DMA access?
>> Sorry about the code still not done and thanks in advance.
>
>     Sorry I'm not really an ARM expert, but this has come up in the list
>     archive before.  You should look at some of the other ARM drivers
>     in the
>     tree...
>
>     Lee
>
>
>
Hi Boku,

I'm not an expert but I recently looked into this.

Frame: From the macro  bytes_to_frames() I gather that a frame is a 
sample. For example, if the sample size is 16 bits, the frame is also 16 
bits. That means that for every 2 bytes sent, one frame is sent.

Period: It is driver dependent. It's the dma interrupt interval. It is 
used to calculate latencies. For example, if a driver can only dma 1024 
bytes at a time, the period will be 1024. That means during capture at 
least 1024 bytes will be received before the first byte is passed to the 
alsa middle layer.

I hope this helps,


Carlos


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Re: Fwd: memory allocate for substream->runtime->dma_area

[Lee Revell]

On Thu, 2006-03-16 at 16:45 -0800, Carlos Munoz wrote:
> Frame: From the macro  bytes_to_frames() I gather that a frame is a 
> sample. For example, if the sample size is 16 bits, the frame is also
> 16 bits. That means that for every 2 bytes sent, one frame is sent.
> 

It's a sample for each channel.  Your example is correct for mono only.
For standard CD format (stereo, 16 bits per sample) a frame is 4 bytes.

Lee



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Re: Fwd: memory allocate for substream->runtime->dma_area

[boku]

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About the dedicated DMA space, if I use ioremap to set the DMA address space
and assign runtime->dma_area point to it, all the data access within the
address space must use ioread/write instead of direct dereference. What
should I do in this case?  Thanks!~

BR,

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Re: Fwd: memory allocate for substream->runtime->dma_area

[Takashi Iwai]

At Fri, 17 Mar 2006 11:26:49 +0800,
boku wrote:
> 
> About the dedicated DMA space, if I use ioremap to set the DMA address space and
> assign runtime->dma_area point to it, all the data access within the address space
> must use ioread/write instead of direct dereference. What should I do in this case? 

In such a case, define copy and silence callbacks.  The latter is
necessary only for playback.  In addition, use snd_pcm_lib_mmap_iomem
as the mmap callback.  You can find an example in nm256.c.

BTW, in nm256.c, the callbacks are ifdef'ed  with i386.  It's because
i386 can access ioremapped area via normal memory read/write.


Takashi


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