[alsa-devel] [PATCH 3/3] ALSA: usb-audio: Move configuration to prepare.

[Takashi Iwai]

At Tue, 18 Sep 2012 10:20:43 +0200,
Takashi Iwai wrote:
> 
> At Mon, 17 Sep 2012 13:11:39 -0700,
> Dylan Reid wrote:
> > 
> > Move interface and endpoint configuration from hw_params to prepare
> > callback.  During system suspend/resume when the USB device power isn't
> > cycled the interface and endpoint configuration need to be set before
> > audio playback can continue.  Resume involves another call to prepare
> > but not to hw_params, moving it here allows a playing stream to continue
> > after resume.
> > 
> > Change-Id: I6a34251c1245352ff2b9f004d781afcb3bf7cda2
> > Signed-off-by: Dylan Reid <dgreid at chromium.org>
> 
> I don't think we need to set up EP unconditionally in the prepare.
> For normal operations, setting up in hw_params makes more sense, as
> it's necessary done only once.
> 
> So, maybe better to add some flag indicating that the re-setup is
> needed in prepare, and set it in the suspend callback.

I meant the patch like below.


Takashi

===

From: Takashi Iwai <tiwai at suse.de>
Subject: [PATCH] ALSA: usb-audio: Avoid unnecessary EP setups in prepare

The recent fix for USB suspend breakage moved the code to set up EP
from hw_params to prepare, but it means also the EP setup might be
called multiple times unnecessarily because the prepare callback can
be called multiple times without starting the stream (e.g. OSS
emulation).

This patch adds a new flag to struct snd_usb_substream indicating
whether the setup of EP is required, and do it only when necessary,
i.e. right after open or suspend.

Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/usb/card.c |  2 ++
 sound/usb/card.h |  1 +
 sound/usb/pcm.c  | 10 +++++++---
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 4a469f0..561bb74 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -646,6 +646,8 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
 			list_for_each(p, &chip->pcm_list) {
 				as = list_entry(p, struct snd_usb_stream, list);
 				snd_pcm_suspend_all(as->pcm);
+				as->substream[0].need_setup_ep =
+					as->substream[1].need_setup_ep = true;
 			}
  		}
 	} else {
diff --git a/sound/usb/card.h b/sound/usb/card.h
index 6cc883c..afa4f9e 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -125,6 +125,7 @@ struct snd_usb_substream {
 	struct snd_usb_endpoint *data_endpoint;
 	struct snd_usb_endpoint *sync_endpoint;
 	unsigned long flags;
+	bool need_setup_ep;		/* (re)configure EP at prepare? */
 
 	u64 formats;			/* format bitmasks (all or'ed) */
 	unsigned int num_formats;		/* number of supported audio formats (list) */
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index d19ff07..ceb3342 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -569,9 +569,12 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 	if (ret < 0)
 		return ret;
 
-	ret = configure_endpoint(subs);
-	if (ret < 0)
-		return ret;
+	if (subs->need_setup_ep) {
+		ret = configure_endpoint(subs);
+		if (ret < 0)
+			return ret;
+		subs->need_setup_ep = false;
+	}
 
 	/* some unit conversions in runtime */
 	subs->data_endpoint->maxframesize =
@@ -983,6 +986,7 @@ static int snd_usb_pcm_open(struct snd_pcm_substream *substream, int direction)
 	runtime->hw = snd_usb_hardware;
 	runtime->private_data = subs;
 	subs->pcm_substream = substream;
+	subs->need_setup_ep = true;
 	/* runtime PM is also done there */
 	return setup_hw_info(runtime, subs);
 }
-- 
1.7.11.5