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From: Takashi Iwai <tiwai@suse.de>
To: "Sridharan, Ranjani" <ranjani.sridharan@intel.com>
Cc: Linux-ALSA <alsa-devel@alsa-project.org>,
	Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Subject: Re: [alsa-devel] [PATCH 7/8] ALSA: pcm: Add card sync_irq field
Date: Mon, 18 Nov 2019 20:49:29 +0100
Message-ID: <s5hpnhpyng6.wl-tiwai@suse.de> (raw)
In-Reply-To: <CAFQqKeWgqHwrCSSbLrkuCHkBww2g4dsBcF93SDN_ZK_-KSe5tg@mail.gmail.com>

On Mon, 18 Nov 2019 20:20:41 +0100,
Sridharan, Ranjani wrote:
> 
> On Mon, Nov 18, 2019 at 10:54 AM Takashi Iwai <tiwai@suse.de> wrote:
> 
>     On Mon, 18 Nov 2019 17:38:49 +0100,
>     Pierre-Louis Bossart wrote:
>     >
>     >
>     >
>     > On 11/17/19 2:53 AM, Takashi Iwai wrote:
>     > > Many PCI and other drivers performs snd_pcm_period_elapsed() simply in
>     > > its interrupt handler, so the sync_stop operation is just to call
>     > > synchronize_irq().  Instead of putting this call multiple times,
>     > > introduce the common card->sync_irq field.  When this field is set,
>     > > PCM core performs synchronize_irq() for sync-stop operation.  Each
>     > > driver just needs to copy its local IRQ number to card->sync_irq, and
>     > > that's all we need.
>     >
>     > Maybe a red-herring or complete non-sense, but I wonder if this is
>     > going to get in the way of Ranjani's multi-client work, where we could
>     > have multiple cards created but with a single IRQ handled by the
>     > parent PCI device?
>     >
>     > Ranjani, you may want to double-check this and chime in, thanks!
>    
>     The synchronize_irq() is fairly safe to call multiple times, and I
>     don't think any problem by invoking it for multi-clients sharing the
>     same IRQ.  For example, Digigram miXart driver creates multiple card
>     objects from a single PCI entry, and I already thought of that
>     possibility; they set the same card->sync_irq value to all card
>     objects, which eventually will call synchronize_irq() multiple times.
>      From the performance POV, this shouldn't be a big problem, because
>     the place calling this is only at hw_params, prepare and hw_free,
>     neither are hot-path.
> 
> Thanks for the clarification, Takashi. But just wondering how would one pass
> on the sync_irq when the snd_card is created? Typically in the case of the
> Intel platforms, the card->dev points to the platform device for the machine
> driver that registers the card and the PCI device is the parent of the machine
> drv platform device. 

It's completely up to the driver implementation :)
You can implement the own sync_stop ops if that's easier, too.

In general, the driver can set up card->sync_irq when the
request_irq() or its variant is called.


Takashi
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Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-17  8:53 [alsa-devel] [PATCH 0/8] ALSA: pcm: API cleanups and extensions Takashi Iwai
2019-11-17  8:53 ` [alsa-devel] [PATCH 1/8] ALSA: pcm: Introduce managed buffer allocation mode Takashi Iwai
2019-11-18 16:24   ` Pierre-Louis Bossart
2019-11-18 18:46     ` Takashi Iwai
2019-11-17  8:53 ` [alsa-devel] [PATCH 2/8] ALSA: docs: Update for " Takashi Iwai
2019-11-17  8:53 ` [alsa-devel] [PATCH 3/8] ALSA: pcm: Allow NULL ioctl ops Takashi Iwai
2019-11-17  8:53 ` [alsa-devel] [PATCH 4/8] ALSA: docs: Update document about the default PCM " Takashi Iwai
2019-11-17  8:53 ` [alsa-devel] [PATCH 5/8] ALSA: pcm: Move PCM_RUNTIME_CHECK() macro into local header Takashi Iwai
2019-11-17  9:42   ` kbuild test robot
2019-11-17 10:05     ` Takashi Iwai
2019-11-17 10:28   ` kbuild test robot
2019-11-17  8:53 ` [alsa-devel] [PATCH 6/8] ALSA: pcm: Add the support for sync-stop operation Takashi Iwai
2019-11-18 16:33   ` Pierre-Louis Bossart
2019-11-18 18:47     ` Takashi Iwai
2019-11-17  8:53 ` [alsa-devel] [PATCH 7/8] ALSA: pcm: Add card sync_irq field Takashi Iwai
2019-11-18 16:38   ` Pierre-Louis Bossart
2019-11-18 18:52     ` Takashi Iwai
2019-11-18 19:20       ` Sridharan, Ranjani
2019-11-18 19:49         ` Takashi Iwai [this message]
2019-11-18 19:55           ` Sridharan, Ranjani
2019-11-18 20:40             ` Takashi Iwai
2019-11-18 23:47               ` Ranjani Sridharan
2019-11-19  6:44                 ` Takashi Iwai
2019-11-19  7:40                   ` Ranjani Sridharan
2019-11-19  8:24                     ` Takashi Iwai
2019-11-19  9:39                       ` Takashi Iwai
2019-11-19 16:36                       ` Ranjani Sridharan
2019-11-19 21:27                         ` Takashi Iwai
2019-11-19 21:43                           ` Sridharan, Ranjani
2019-11-21 19:22                             ` Sridharan, Ranjani
2019-11-21 20:34                               ` Takashi Iwai
2019-11-21 20:46                                 ` Sridharan, Ranjani
2019-11-21 21:13                                   ` Takashi Iwai
2019-11-21 21:17                                     ` Sridharan, Ranjani
2019-11-21 21:28                                       ` Takashi Iwai
2019-11-21 21:45                                         ` Sridharan, Ranjani
2019-11-22  4:08                                     ` Jie, Yang
2019-11-17  8:53 ` [alsa-devel] [PATCH 8/8] ALSA: docs: Update about the new PCM sync_stop ops Takashi Iwai

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