From: Raymond Yau <superquad.vortex2@gmail.com>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: Takashi Iwai <tiwai@suse.de>,
ALSA Development Mailing List <alsa-devel@alsa-project.org>
Subject: Re: [RFC PATCH 3/4] ALSA: core: add report of max dma burst
Date: Fri, 10 Jul 2015 10:35:51 +0800 [thread overview]
Message-ID: <CAN8cciYf_oz+ozAesHu5j_V0=iDSuFrLM5E2i6f+CbaXqWX9uQ@mail.gmail.com> (raw)
In-Reply-To: <559D61EA.7030308@linux.intel.com>
>
>
>>> FIXME:
>>> 1. this was copy/pasted/edited based on the fifo_size fields, not
>>> sure why we would need this IOCTL1
>>
>>
>> fifo_size would fit, but it means that it also changes the current
>> behavior. I don't believe that currently there are many programs
>> relying on this value, but who knows.
>
>
> I saw a mention of fifo_size in the VIA HDA controller, that's why I went
ahead with a different field. The fifo_size could be useful as a max value
for the internal hardware delay, when app use the 'delay' field in the
status structure they get a very dynamic value that isn't necessarily
straightforward to use.
>
>
>>
>>> 2. we also need the ability to set the actual fifo size, if suppported,
>>> by the hardware, to negociate the prefetch amount between application
>>> and driver. By default the default should be max buffering to allow
>>> for lower power, but for low-latency use cases we may want to reduce
>>> the amount of prefetching.
>>
>>
>> Right. So a hw_parmas field looks suitable for that purpose.
>
>
> That 'set' capability is a lot more complicated, I am really having a
hard time with all the constraints for hw_params and how to represent
min,max and step values... If anyone is willing to help on that part I
wouldn't mind, this is really a part of ALSA I never looked into...
What is the usage of runtime->dma_bytes in
snd_pcm_hw_constraints_complete() in core/pcm_native.c ?
Was the usage similar to 128 bytes alignment ?
/* FIXME: remove */
if (runtime->dma_bytes) {
err = snd_pcm_hw_constraint_minmax(runtime,
SNDRV_PCM_HW_PARAM_BUFFER_BYTES, 0, runtime->dma_bytes);
if (err < 0)
return err;
}
next prev parent reply other threads:[~2015-07-10 2:35 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-08 10:10 [RFC PATCH 0/4] better support for bursty DMA usages Pierre-Louis Bossart
2015-07-08 10:10 ` [RFC PATCH 1/4] ALSA: core: let low-level driver or userspace disable rewinds Pierre-Louis Bossart
2015-07-08 14:21 ` Takashi Iwai
2015-07-08 16:58 ` Pierre-Louis Bossart
2015-07-11 17:06 ` Alexander E. Patrakov
2015-07-14 3:32 ` Raymond Yau
2015-07-14 17:39 ` Alexander E. Patrakov
2015-07-15 1:23 ` Raymond Yau
2015-07-15 4:51 ` Alexander E. Patrakov
2015-07-28 14:19 ` Pierre-Louis Bossart
2015-07-28 15:43 ` Alexander E. Patrakov
2015-07-29 17:46 ` Pierre-Louis Bossart
2015-07-30 6:11 ` Alexander E. Patrakov
2015-07-30 13:46 ` Pierre-Louis Bossart
2015-07-08 10:10 ` [RFC PATCH 2/4] ALSA: core: add .notify callback for pcm ops Pierre-Louis Bossart
2015-07-08 14:27 ` Takashi Iwai
2015-07-08 17:10 ` Pierre-Louis Bossart
2015-07-09 14:44 ` Takashi Iwai
2015-07-09 7:25 ` Raymond Yau
2015-07-09 7:35 ` Pierre-Louis Bossart
2015-07-08 10:10 ` [RFC PATCH 3/4] ALSA: core: add report of max dma burst Pierre-Louis Bossart
2015-07-08 14:37 ` Takashi Iwai
2015-07-08 17:46 ` Pierre-Louis Bossart
2015-07-10 2:35 ` Raymond Yau [this message]
2015-07-10 17:13 ` Lars-Peter Clausen
2015-07-11 17:46 ` Alexander E. Patrakov
2015-07-11 18:28 ` Jaroslav Kysela
2015-07-16 2:11 ` Raymond Yau
2015-07-08 10:10 ` [RFC PATCH 4/4] ALSA: hda: add default value for max_dma_burst Pierre-Louis Bossart
2015-07-08 14:31 ` [RFC PATCH 0/4] better support for bursty DMA usages Takashi Iwai
2015-07-08 17:50 ` Pierre-Louis Bossart
2015-07-15 10:14 ` Raymond Yau
2015-07-15 10:38 ` Alexander E. Patrakov
2015-07-22 14:44 ` Raymond Yau
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