linux-kernel - [PATCH v3 4/4] usb: gadget: u

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Date:   Mon, 18 Jan 2021 09:49:31 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Ruslan Bilovol <ruslan.bilovol@...il.com>,
        Jack Pham <jackp@...eaurora.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 4/4] usb: gadget: u_audio: clean up locking

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.

Acked-by: Felipe Balbi <balbi@...nel.org>
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
---
 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 a1a1f4c8685c..265c4d805f81 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