ALSA: firewire-motu: postpone sound card registration

Just after appearing on IEEE 1394 bus, this unit generates several bus
resets. This is due to loading firmware from on-board flash memory and
initialize hardware. It's better to postpone sound card registration.

This commit applies this idea.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 78 insertions, 24 deletions

diff --git a/sound/firewire/motu/motu.c b/sound/firewire/motu/motu.c
index 2684e7447432..bdd82ddeb6ec 100644
--- a/sound/firewire/motu/motu.c
+++ b/sound/firewire/motu/motu.c
@@ -38,59 +38,108 @@ static void name_card(struct snd_motu *motu)
                  dev_name(&motu->unit->device), 100 << fw_dev->max_speed);
 }
 
-static void motu_card_free(struct snd_card *card)
+static void motu_free(struct snd_motu *motu)
 {
-        struct snd_motu *motu = card->private_data;
-
         fw_unit_put(motu->unit);
 
         mutex_destroy(&motu->mutex);
+        kfree(motu);
 }
 
-static int motu_probe(struct fw_unit *unit,
-                      const struct ieee1394_device_id *entry)
+/*
+ * This module releases the FireWire unit data after all ALSA character devices
+ * are released by applications. This is for releasing stream data or finishing
+ * transactions safely. Thus at returning from .remove(), this module still keep
+ * references for the unit.
+ */
+static void motu_card_free(struct snd_card *card)
 {
-        struct snd_card *card;
-        struct snd_motu *motu;
-        int err;
+        motu_free(card->private_data);
+}
 
-        err = snd_card_new(&unit->device, -1, NULL, THIS_MODULE,
-                           sizeof(*motu), &card);
-        if (err < 0)
-                return err;
+static void do_registration(struct work_struct *work)
+{
+        struct snd_motu *motu = container_of(work, struct snd_motu, dwork.work);
+        int err;
 
-        motu = card->private_data;
-        motu->card = card;
-        motu->unit = fw_unit_get(unit);
-        card->private_free = motu_card_free;
+        if (motu->registered)
+                return;
 
-        mutex_init(&motu->mutex);
+        err = snd_card_new(&motu->unit->device, -1, NULL, THIS_MODULE, 0,
+                           &motu->card);
+        if (err < 0)
+                return;
 
         name_card(motu);
 
-        err = snd_card_register(card);
+        err = snd_card_register(motu->card);
         if (err < 0)
                 goto error;
 
+        /*
+         * After registered, motu instance can be released corresponding to
+         * releasing the sound card instance.
+         */
+        motu->card->private_free = motu_card_free;
+        motu->card->private_data = motu;
+        motu->registered = true;
+
+        return;
+error:
+        snd_card_free(motu->card);
+        dev_info(&motu->unit->device,
+                 "Sound card registration failed: %d\n", err);
+}
+
+static int motu_probe(struct fw_unit *unit,
+                      const struct ieee1394_device_id *entry)
+{
+        struct snd_motu *motu;
+
+        /* Allocate this independently of sound card instance. */
+        motu = kzalloc(sizeof(struct snd_motu), GFP_KERNEL);
+        if (motu == NULL)
+                return -ENOMEM;
+
+        motu->unit = fw_unit_get(unit);
         dev_set_drvdata(&unit->device, motu);
 
+        mutex_init(&motu->mutex);
+
+        /* Allocate and register this sound card later. */
+        INIT_DEFERRABLE_WORK(&motu->dwork, do_registration);
+        snd_fw_schedule_registration(unit, &motu->dwork);
+
         return 0;
-error:
-        snd_card_free(card);
-        return err;
 }
 
 static void motu_remove(struct fw_unit *unit)
 {
         struct snd_motu *motu = dev_get_drvdata(&unit->device);
 
-        /* No need to wait for releasing card object in this context. */
-        snd_card_free_when_closed(motu->card);
+        /*
+         * Confirm to stop the work for registration before the sound card is
+         * going to be released. The work is not scheduled again because bus
+         * reset handler is not called anymore.
+         */
+        cancel_delayed_work_sync(&motu->dwork);
+
+        if (motu->registered) {
+                /* No need to wait for releasing card object in this context. */
+                snd_card_free_when_closed(motu->card);
+        } else {
+                /* Don't forget this case. */
+                motu_free(motu);
+        }
 }
 
 static void motu_bus_update(struct fw_unit *unit)
 {
-        return;
+        struct snd_motu *motu = dev_get_drvdata(&unit->device);
+
+        /* Postpone a workqueue for deferred registration. */
+        if (!motu->registered)
+                snd_fw_schedule_registration(unit, &motu->dwork);
 }
 
 #define SND_MOTU_DEV_ENTRY(model)                       \
diff --git a/sound/firewire/motu/motu.h b/sound/firewire/motu/motu.h
index f3d0b2834942..eb0ffd56c835 100644
--- a/sound/firewire/motu/motu.h
+++ b/sound/firewire/motu/motu.h
@@ -20,10 +20,15 @@
 #include <sound/control.h>
 #include <sound/core.h>
 
+#include "../lib.h"
+
 struct snd_motu {
         struct snd_card *card;
         struct fw_unit *unit;
         struct mutex mutex;
+
+        bool registered;
+        struct delayed_work dwork;
 };
 
 #endif