[PATCH v2 5/5] usb: gadget: u_audio: clean up locking

From: Jerome Brunet
Date: Wed Jan 06 2021 - 08:38:46 EST


snd_pcm_stream_lock() is held when the ALSA .trigger() callback is called.
The lock of 'struct uac_rtd_params' is not necessary since all its locking
operation are done under the snd_pcm_stream_lock() too.

Also, usb_request .complete() is called with irqs disabled, so saving and
restoring the irqs is not necessary.

Signed-off-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
---
drivers/usb/gadget/function/u_audio.c | 23 ++++-------------------
1 file changed, 4 insertions(+), 19 deletions(-)

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index 1d12657b3b73..e985630fbe6e 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -36,9 +36,8 @@ struct uac_rtd_params {
void *rbuf;

unsigned int max_psize; /* MaxPacketSize of endpoint */
- struct usb_request **reqs;

- spinlock_t lock;
+ struct usb_request **reqs;
};

struct snd_uac_chip {
@@ -74,7 +73,6 @@ static const struct snd_pcm_hardware uac_pcm_hardware = {
static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
{
unsigned int pending;
- unsigned long flags, flags2;
unsigned int hw_ptr;
int status = req->status;
struct snd_pcm_substream *substream;
@@ -105,16 +103,14 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
if (!substream)
goto exit;

- snd_pcm_stream_lock_irqsave(substream, flags2);
+ snd_pcm_stream_lock(substream);

runtime = substream->runtime;
if (!runtime || !snd_pcm_running(substream)) {
- snd_pcm_stream_unlock_irqrestore(substream, flags2);
+ snd_pcm_stream_unlock(substream);
goto exit;
}

- spin_lock_irqsave(&prm->lock, flags);
-
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
/*
* For each IN packet, take the quotient of the current data
@@ -141,8 +137,6 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)

hw_ptr = prm->hw_ptr;

- spin_unlock_irqrestore(&prm->lock, flags);
-
/* Pack USB load in ALSA ring buffer */
pending = runtime->dma_bytes - hw_ptr;

@@ -166,12 +160,10 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
}
}

- spin_lock_irqsave(&prm->lock, flags);
/* update hw_ptr after data is copied to memory */
prm->hw_ptr = (hw_ptr + req->actual) % runtime->dma_bytes;
hw_ptr = prm->hw_ptr;
- spin_unlock_irqrestore(&prm->lock, flags);
- snd_pcm_stream_unlock_irqrestore(substream, flags2);
+ snd_pcm_stream_unlock(substream);

if ((hw_ptr % snd_pcm_lib_period_bytes(substream)) < req->actual)
snd_pcm_period_elapsed(substream);
@@ -187,7 +179,6 @@ static int uac_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
struct uac_rtd_params *prm;
struct g_audio *audio_dev;
struct uac_params *params;
- unsigned long flags;
int err = 0;

audio_dev = uac->audio_dev;
@@ -198,8 +189,6 @@ static int uac_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
else
prm = &uac->c_prm;

- spin_lock_irqsave(&prm->lock, flags);
-
/* Reset */
prm->hw_ptr = 0;

@@ -216,8 +205,6 @@ static int uac_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
err = -EINVAL;
}

- spin_unlock_irqrestore(&prm->lock, flags);
-
/* Clear buffer after Play stops */
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK && !prm->ss)
memset(prm->rbuf, 0, prm->max_psize * params->req_number);
@@ -280,14 +267,12 @@ static int uac_pcm_open(struct snd_pcm_substream *substream)
runtime->hw = uac_pcm_hardware;

if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
- spin_lock_init(&uac->p_prm.lock);
runtime->hw.rate_min = p_srate;
runtime->hw.formats = uac_ssize_to_fmt(p_ssize);
runtime->hw.channels_min = num_channels(p_chmask);
runtime->hw.period_bytes_min = 2 * uac->p_prm.max_psize
/ runtime->hw.periods_min;
} else {
- spin_lock_init(&uac->c_prm.lock);
runtime->hw.rate_min = c_srate;
runtime->hw.formats = uac_ssize_to_fmt(c_ssize);
runtime->hw.channels_min = num_channels(c_chmask);
--
2.29.2