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ALSA: usb-audio: Pre-calculate buffer byte size
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There are a bunch of lines calculating the buffer size in bytes at
each time.  Keep the value in subs->buffer_bytes and use it
consistently for the code simplicity.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>
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@tiwai
tiwai committed Jun 2, 2021
1 parent cdebd55 commit d303c5d
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Showing 2 changed files with 25 additions and 24 deletions.
1 change: 1 addition & 0 deletions sound/usb/card.h
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,7 @@ struct snd_usb_substream {

unsigned int running: 1; /* running status */

unsigned int buffer_bytes; /* buffer size in bytes */
unsigned int hwptr_done; /* processed byte position in the buffer */
unsigned int transfer_done; /* processed frames since last period update */
unsigned int frame_limit; /* limits number of packets in URB */
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48 changes: 24 additions & 24 deletions sound/usb/pcm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -600,6 +600,7 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
goto unlock;

/* reset the pointer */
subs->buffer_bytes = frames_to_bytes(runtime, runtime->buffer_size);
subs->hwptr_done = 0;
subs->transfer_done = 0;
subs->last_delay = 0;
Expand Down Expand Up @@ -1147,8 +1148,8 @@ static void retire_capture_urb(struct snd_usb_substream *subs,
spin_lock_irqsave(&subs->lock, flags);
oldptr = subs->hwptr_done;
subs->hwptr_done += bytes;
if (subs->hwptr_done >= runtime->buffer_size * stride)
subs->hwptr_done -= runtime->buffer_size * stride;
if (subs->hwptr_done >= subs->buffer_bytes)
subs->hwptr_done -= subs->buffer_bytes;
frames = (bytes + (oldptr % stride)) / stride;
subs->transfer_done += frames;
if (subs->transfer_done >= runtime->period_size) {
Expand All @@ -1166,9 +1167,9 @@ static void retire_capture_urb(struct snd_usb_substream *subs,

spin_unlock_irqrestore(&subs->lock, flags);
/* copy a data chunk */
if (oldptr + bytes > runtime->buffer_size * stride) {
unsigned int bytes1 =
runtime->buffer_size * stride - oldptr;
if (oldptr + bytes > subs->buffer_bytes) {
unsigned int bytes1 = subs->buffer_bytes - oldptr;

memcpy(runtime->dma_area + oldptr, cp, bytes1);
memcpy(runtime->dma_area, cp + bytes1, bytes - bytes1);
} else {
Expand All @@ -1184,10 +1185,9 @@ static inline void fill_playback_urb_dsd_dop(struct snd_usb_substream *subs,
struct urb *urb, unsigned int bytes)
{
struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
unsigned int stride = runtime->frame_bits >> 3;
unsigned int dst_idx = 0;
unsigned int src_idx = subs->hwptr_done;
unsigned int wrap = runtime->buffer_size * stride;
unsigned int wrap = subs->buffer_bytes;
u8 *dst = urb->transfer_buffer;
u8 *src = runtime->dma_area;
u8 marker[] = { 0x05, 0xfa };
Expand Down Expand Up @@ -1233,19 +1233,19 @@ static inline void fill_playback_urb_dsd_dop(struct snd_usb_substream *subs,
subs->hwptr_done++;
}
}
if (subs->hwptr_done >= runtime->buffer_size * stride)
subs->hwptr_done -= runtime->buffer_size * stride;
if (subs->hwptr_done >= subs->buffer_bytes)
subs->hwptr_done -= subs->buffer_bytes;
}

static void copy_to_urb(struct snd_usb_substream *subs, struct urb *urb,
int offset, int stride, unsigned int bytes)
{
struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;

if (subs->hwptr_done + bytes > runtime->buffer_size * stride) {
if (subs->hwptr_done + bytes > subs->buffer_bytes) {
/* err, the transferred area goes over buffer boundary. */
unsigned int bytes1 =
runtime->buffer_size * stride - subs->hwptr_done;
unsigned int bytes1 = subs->buffer_bytes - subs->hwptr_done;

memcpy(urb->transfer_buffer + offset,
runtime->dma_area + subs->hwptr_done, bytes1);
memcpy(urb->transfer_buffer + offset + bytes1,
Expand All @@ -1255,8 +1255,8 @@ static void copy_to_urb(struct snd_usb_substream *subs, struct urb *urb,
runtime->dma_area + subs->hwptr_done, bytes);
}
subs->hwptr_done += bytes;
if (subs->hwptr_done >= runtime->buffer_size * stride)
subs->hwptr_done -= runtime->buffer_size * stride;
if (subs->hwptr_done >= subs->buffer_bytes)
subs->hwptr_done -= subs->buffer_bytes;
}

static unsigned int copy_to_urb_quirk(struct snd_usb_substream *subs,
Expand Down Expand Up @@ -1295,7 +1295,7 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
int i, stride, period_elapsed = 0;
unsigned long flags;

stride = runtime->frame_bits >> 3;
stride = ep->stride;

frames = 0;
urb->number_of_packets = 0;
Expand All @@ -1304,8 +1304,8 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
for (i = 0; i < ctx->packets; i++) {
counts = snd_usb_endpoint_next_packet_size(ep, ctx, i);
/* set up descriptor */
urb->iso_frame_desc[i].offset = frames * ep->stride;
urb->iso_frame_desc[i].length = counts * ep->stride;
urb->iso_frame_desc[i].offset = frames * stride;
urb->iso_frame_desc[i].length = counts * stride;
frames += counts;
urb->number_of_packets++;
subs->transfer_done += counts;
Expand All @@ -1320,14 +1320,14 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
frames -= subs->transfer_done;
counts -= subs->transfer_done;
urb->iso_frame_desc[i].length =
counts * ep->stride;
counts * stride;
subs->transfer_done = 0;
}
i++;
if (i < ctx->packets) {
/* add a transfer delimiter */
urb->iso_frame_desc[i].offset =
frames * ep->stride;
frames * stride;
urb->iso_frame_desc[i].length = 0;
urb->number_of_packets++;
}
Expand All @@ -1340,7 +1340,7 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
!snd_usb_endpoint_implicit_feedback_sink(ep))
break;
}
bytes = frames * ep->stride;
bytes = frames * stride;

if (unlikely(ep->cur_format == SNDRV_PCM_FORMAT_DSD_U16_LE &&
subs->cur_audiofmt->dsd_dop)) {
Expand All @@ -1350,14 +1350,14 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
/* bit-reverse the bytes */
u8 *buf = urb->transfer_buffer;
for (i = 0; i < bytes; i++) {
int idx = (subs->hwptr_done + i)
% (runtime->buffer_size * stride);
int idx = (subs->hwptr_done + i) % subs->buffer_bytes;

buf[i] = bitrev8(runtime->dma_area[idx]);
}

subs->hwptr_done += bytes;
if (subs->hwptr_done >= runtime->buffer_size * stride)
subs->hwptr_done -= runtime->buffer_size * stride;
if (subs->hwptr_done >= subs->buffer_bytes)
subs->hwptr_done -= subs->buffer_bytes;
} else {
/* usual PCM */
if (!subs->tx_length_quirk)
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