ENGR00170819-1 usb-gadget: add usb audio support

- Only 44.1Khz audio are supported at i.MX6q, since only 44.1Khz
local playback are supported at i.MX6q.

- Since there is no feedback at current usb audio framework,
it may have pop noise/no sound after play some minutes.

- About how to test: please refer Documentation/arm/imx/udc.txt

Signed-off-by: Peter Chen <peter.chen@freescale.com>

2 files changed, 45 insertions, 8 deletions

diff --git a/drivers/usb/gadget/f_audio.c b/drivers/usb/gadget/f_audio.c
index 3af0895469f3..2d285ec6e8bc 100644
--- a/drivers/usb/gadget/f_audio.c
+++ b/drivers/usb/gadget/f_audio.c
@@ -29,9 +29,16 @@ static int audio_buf_size = 48000;
 module_param(audio_buf_size, int, S_IRUGO);
 MODULE_PARM_DESC(audio_buf_size, "Audio buffer size");
 
+/* The first usb audio buf to alsa playback */
+static int first_audio_buf_size = 65500;
+module_param(first_audio_buf_size, int, S_IRUGO);
+MODULE_PARM_DESC(first_audio_buf_size, "First Audio buffer size");
+
 static int generic_set_cmd(struct usb_audio_control *con, u8 cmd, int value);
 static int generic_get_cmd(struct usb_audio_control *con, u8 cmd);
 
+/* Flag to use buffer with first_audio_buf_size to asla */
+static int first_copy_audio_buffer = 1;
 /*
  * DESCRIPTORS ... most are static, but strings and full
  * configuration descriptors are built on demand.
@@ -329,13 +336,27 @@ static int f_audio_out_ep_complete(struct usb_ep *ep, struct usb_request *req)
 	if (!copy_buf)
 		return -EINVAL;
 
+	if (!first_copy_audio_buffer) {
 	/* Copy buffer is full, add it to the play_queue */
-	if (audio_buf_size - copy_buf->actual < req->actual) {
-		list_add_tail(&copy_buf->list, &audio->play_queue);
-		schedule_work(&audio->playback_work);
-		copy_buf = f_audio_buffer_alloc(audio_buf_size);
-		if (IS_ERR(copy_buf))
-			return -ENOMEM;
+		if (audio_buf_size - copy_buf->actual < req->actual) {
+			list_add_tail(&copy_buf->list, &audio->play_queue);
+			schedule_work(&audio->playback_work);
+			copy_buf = f_audio_buffer_alloc(audio_buf_size);
+
+			if (IS_ERR(copy_buf))
+				return -ENOMEM;
+		}
+	} else {
+		if (first_audio_buf_size - copy_buf->actual < req->actual) {
+			list_add_tail(&copy_buf->list, &audio->play_queue);
+			schedule_work(&audio->playback_work);
+			copy_buf = f_audio_buffer_alloc(audio_buf_size);
+
+			if (IS_ERR(copy_buf))
+				return -ENOMEM;
+
+			first_copy_audio_buffer = 0;
+		}
 	}
 
 	memcpy(copy_buf->buf + copy_buf->actual, req->buf, req->actual);
@@ -577,7 +598,7 @@ static int f_audio_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 		if (alt == 1) {
 			usb_ep_enable(out_ep, audio->out_desc);
 			out_ep->driver_data = audio;
-			audio->copy_buf = f_audio_buffer_alloc(audio_buf_size);
+			audio->copy_buf = f_audio_buffer_alloc(first_audio_buf_size);
 			if (IS_ERR(audio->copy_buf))
 				return -ENOMEM;
 
@@ -614,6 +635,7 @@ static int f_audio_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 						&audio->play_queue);
 				schedule_work(&audio->playback_work);
 			}
+			first_copy_audio_buffer = 1;
 		}
 	}
 
diff --git a/drivers/usb/gadget/u_audio.c b/drivers/usb/gadget/u_audio.c
index 59ffe1ecf1c9..c72aeca692ed 100644
--- a/drivers/usb/gadget/u_audio.c
+++ b/drivers/usb/gadget/u_audio.c
@@ -39,6 +39,10 @@ static char *fn_cntl = FILE_CONTROL;
 module_param(fn_cntl, charp, S_IRUGO);
 MODULE_PARM_DESC(fn_cntl, "Control device file name");
 
+static int audio_sample_rate = 48000;
+module_param(audio_sample_rate, int, S_IRUGO);
+MODULE_PARM_DESC(audio_sample_rate, "Audio Sample Rate");
+
 /*-------------------------------------------------------------------------*/
 
 /**
@@ -122,13 +126,23 @@ static int playback_default_hw_params(struct gaudio_snd_dev *snd)
 	snd->access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
 	snd->format = SNDRV_PCM_FORMAT_S16_LE;
 	snd->channels = 2;
-	snd->rate = 48000;
+	if (audio_sample_rate == 44100)
+		snd->rate = 44100;
+	else if (audio_sample_rate == 48000)
+		snd->rate = 48000;
 
 	params = kzalloc(sizeof(*params), GFP_KERNEL);
 	if (!params)
 		return -ENOMEM;
 
 	_snd_pcm_hw_params_any(params);
+
+	if (audio_sample_rate == 44100) {
+		_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, \
+					       2*1024, 0);
+		_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_BUFFER_SIZE, \
+						       16*1024, 0);
+	}
 	_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_ACCESS,
 			snd->access, 0);
 	_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_FORMAT,
@@ -193,6 +207,7 @@ try_again:
 	set_fs(KERNEL_DS);
 	result = snd_pcm_lib_write(snd->substream, buf, frames);
 	if (result != frames) {
+		msleep_interruptible(2);
 		ERROR(card, "Playback error: %d\n", (int)result);
 		set_fs(old_fs);
 		goto try_again;