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From: Greg KH on 1 Jul 2010 18:10
2.6.34-stable review patch. If anyone has any objections, please let me know.

------------------

From: Clemens Ladisch <clemens(a)ladisch.de>

commit ead4046b2fdfd69acc4272e693afd249ad3eb689 upstream.

Commit 7910b4a1db63fefc3d291853d33c34c5b6352e8e in 2.6.34 changed the
runtime->boundary calculation to make this value a multiple of both the
buffer_size and the period_size, because the latter is assumed by the
runtime->hw_ptr_interrupt calculation.

However, due to the lack of a ioctl that could read the software
parameters before they are set, the kernel requires that alsa-lib
calculates the boundary value, too. The changed algorithm leads to
a different boundary value used by alsa-lib, which makes, e.g., mplayer
fail to play a 44.1 kHz file because the silence_size parameter is now
invalid; bug report:
<https://bugtrack.alsa-project.org/alsa-bug/view.php?id=5015>.

This patch reverts the change to the boundary calculation, and instead
fixes the hw_ptr_interrupt calculation to be period-aligned regardless
of the boundary value.

Signed-off-by: Clemens Ladisch <clemens(a)ladisch.de>
Signed-off-by: Takashi Iwai <tiwai(a)suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
sound/core/pcm_lib.c | 9 +++++++--
sound/core/pcm_native.c | 39 +++------------------------------------
2 files changed, 10 insertions(+), 38 deletions(-)

--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -441,8 +441,13 @@ static int snd_pcm_update_hw_ptr0(struct
snd_pcm_playback_silence(substream, new_hw_ptr);

if (in_interrupt) {
- runtime->hw_ptr_interrupt = new_hw_ptr -
- (new_hw_ptr % runtime->period_size);
+ delta = new_hw_ptr - runtime->hw_ptr_interrupt;
+ if (delta < 0)
+ delta += runtime->boundary;
+ delta -= (snd_pcm_uframes_t)delta % runtime->period_size;
+ runtime->hw_ptr_interrupt += delta;
+ if (runtime->hw_ptr_interrupt >= runtime->boundary)
+ runtime->hw_ptr_interrupt -= runtime->boundary;
}
runtime->hw_ptr_base = hw_base;
runtime->status->hw_ptr = new_hw_ptr;
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -27,7 +27,6 @@
#include <linux/pm_qos_params.h>
#include <linux/uio.h>
#include <linux/dma-mapping.h>
-#include <linux/math64.h>
#include <sound/core.h>
#include <sound/control.h>
#include <sound/info.h>
@@ -370,38 +369,6 @@ static int period_to_usecs(struct snd_pc
return usecs;
}

-static int calc_boundary(struct snd_pcm_runtime *runtime)
-{
- u_int64_t boundary;
-
- boundary = (u_int64_t)runtime->buffer_size *
- (u_int64_t)runtime->period_size;
-#if BITS_PER_LONG < 64
- /* try to find lowest common multiple for buffer and period */
- if (boundary > LONG_MAX - runtime->buffer_size) {
- u_int32_t remainder = -1;
- u_int32_t divident = runtime->buffer_size;
- u_int32_t divisor = runtime->period_size;
- while (remainder) {
- remainder = divident % divisor;
- if (remainder) {
- divident = divisor;
- divisor = remainder;
- }
- }
- boundary = div_u64(boundary, divisor);
- if (boundary > LONG_MAX - runtime->buffer_size)
- return -ERANGE;
- }
-#endif
- if (boundary == 0)
- return -ERANGE;
- runtime->boundary = boundary;
- while (runtime->boundary * 2 <= LONG_MAX - runtime->buffer_size)
- runtime->boundary *= 2;
- return 0;
-}
-
static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
struct snd_pcm_hw_params *params)
{
@@ -477,9 +444,9 @@ static int snd_pcm_hw_params(struct snd_
runtime->stop_threshold = runtime->buffer_size;
runtime->silence_threshold = 0;
runtime->silence_size = 0;
- err = calc_boundary(runtime);
- if (err < 0)
- goto _error;
+ runtime->boundary = runtime->buffer_size;
+ while (runtime->boundary * 2 <= LONG_MAX - runtime->buffer_size)
+ runtime->boundary *= 2;

snd_pcm_timer_resolution_change(substream);
runtime->status->state = SNDRV_PCM_STATE_SETUP;


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