[ALSA] Xilinx ML403 AC97 Controller Reference device driver

Add ALSA support for the opb_ac97_controller_ref_v1_00_a ip core found
in Xilinx' ML403 reference design.
Known issue: Currently this driver hits a WARN_ON_ONCE(1) statement in
kernel/irq/resend.c (line 70). According to Linus
(http://lkml.org/lkml/2007/8/5/5) this may be ignored, right? I haven't
had a look into this 'problem' yet.
Signed-off-by: NJoachim Foerster <JOFT@gmx.de>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@perex.cz>

sound/drivers/Kconfig

@@ -120,4 +120,16 @@ config SND_PORTMAN2X4
 	  To compile this driver as a module, choose M here: the module
 	  will be called snd-portman2x4.
 
+config SND_ML403_AC97CR
+	tristate "Xilinx ML403 AC97 Controller Reference"
+	depends on SND && XILINX_VIRTEX
+	select SND_AC97_CODEC
+	help
+	  Say Y here to include support for the
+	  opb_ac97_controller_ref_v1_00_a ip core found in Xilinx' ML403
+	  reference design.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called snd-ml403_ac97cr.
+
 endmenu

sound/drivers/Makefile

@@ -9,6 +9,7 @@ snd-mts64-objs := mts64.o
 snd-portman2x4-objs := portman2x4.o
 snd-serial-u16550-objs := serial-u16550.o
 snd-virmidi-objs := virmidi.o
+snd-ml403-ac97cr-objs := ml403-ac97cr.o pcm-indirect2.o
 
 # Toplevel Module Dependency
 obj-$(CONFIG_SND_DUMMY) += snd-dummy.o
@@ -17,5 +18,6 @@ obj-$(CONFIG_SND_SERIAL_U16550) += snd-serial-u16550.o
 obj-$(CONFIG_SND_MTPAV) += snd-mtpav.o
 obj-$(CONFIG_SND_MTS64) += snd-mts64.o
 obj-$(CONFIG_SND_PORTMAN2X4) += snd-portman2x4.o
+obj-$(CONFIG_SND_ML403_AC97CR) += snd-ml403-ac97cr.o
 
 obj-$(CONFIG_SND) += opl3/ opl4/ mpu401/ vx/

sound/drivers/pcm-indirect2.c

+/*
+ * Helper functions for indirect PCM data transfer to a simple FIFO in
+ * hardware (small, no possibility to read "hardware io position",
+ * updating position done by interrupt, ...)
+ *
+ *  Copyright (c) by 2007  Joachim Foerster <JOFT@gmx.de>
+ *
+ *  Based on "pcm-indirect.h" (alsa-driver-1.0.13) by
+ *
+ *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
+ *                   Jaroslav Kysela <perex@suse.cz>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* #dependency of sound/core.h# */
+#include <sound/driver.h>
+/* snd_printk/d() */
+#include <sound/core.h>
+/* struct snd_pcm_substream, struct snd_pcm_runtime, snd_pcm_uframes_t
+ * snd_pcm_period_elapsed() */
+#include <sound/pcm.h>
+
+#include "pcm-indirect2.h"
+
+#ifdef SND_PCM_INDIRECT2_STAT
+/* jiffies */
+#include <linux/jiffies.h>
+
+void snd_pcm_indirect2_stat(struct snd_pcm_substream *substream,
+			    struct snd_pcm_indirect2 *rec)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	int i;
+	int j;
+	int k;
+	int seconds = (rec->lastbytetime - rec->firstbytetime) / HZ;
+
+	snd_printk(KERN_DEBUG "STAT: mul_elapsed: %u, mul_elapsed_real: %d, "
+		   "irq_occured: %d\n",
+		   rec->mul_elapsed, rec->mul_elapsed_real, rec->irq_occured);
+	snd_printk(KERN_DEBUG "STAT: min_multiple: %d (irqs/period)\n",
+		   rec->min_multiple);
+	snd_printk(KERN_DEBUG "STAT: firstbytetime: %lu, lastbytetime: %lu, "
+		   "firstzerotime: %lu\n",
+		 rec->firstbytetime, rec->lastbytetime, rec->firstzerotime);
+	snd_printk(KERN_DEBUG "STAT: bytes2hw: %u Bytes => (by runtime->rate) "
+		   "length: %d s\n",
+		 rec->bytes2hw, rec->bytes2hw / 2 / 2 / runtime->rate);
+	snd_printk(KERN_DEBUG "STAT: (by measurement) length: %d => "
+		   "rate: %d Bytes/s = %d Frames/s|Hz\n",
+		   seconds, rec->bytes2hw / seconds,
+		   rec->bytes2hw / 2 / 2 / seconds);
+	snd_printk(KERN_DEBUG
+		   "STAT: zeros2hw: %u = %d ms ~ %d * %d zero copies\n",
+		   rec->zeros2hw, ((rec->zeros2hw / 2 / 2) * 1000) /
+		   runtime->rate,
+		   rec->zeros2hw / (rec->hw_buffer_size / 2),
+		   (rec->hw_buffer_size / 2));
+	snd_printk(KERN_DEBUG "STAT: pointer_calls: %u, lastdifftime: %u\n",
+		   rec->pointer_calls, rec->lastdifftime);
+	snd_printk(KERN_DEBUG "STAT: sw_io: %d, sw_data: %d\n", rec->sw_io,
+		   rec->sw_data);
+	snd_printk(KERN_DEBUG "STAT: byte_sizes[]:\n");
+	k = 0;
+	for (j = 0; j < 8; j++) {
+		for (i = j * 8; i < (j + 1) * 8; i++)
+			if (rec->byte_sizes[i] != 0) {
+				snd_printk(KERN_DEBUG "%u: %u",
+					   i, rec->byte_sizes[i]);
+				k++;
+			}
+		if (((k % 8) == 0) && (k != 0)) {
+			snd_printk(KERN_DEBUG "\n");
+			k = 0;
+		}
+	}
+	snd_printk(KERN_DEBUG "\n");
+	snd_printk(KERN_DEBUG "STAT: zero_sizes[]:\n");
+	for (j = 0; j < 8; j++) {
+		k = 0;
+		for (i = j * 8; i < (j + 1) * 8; i++)
+			if (rec->zero_sizes[i] != 0)
+				snd_printk(KERN_DEBUG "%u: %u",
+					   i, rec->zero_sizes[i]);
+			else
+				k++;
+		if (!k)
+			snd_printk(KERN_DEBUG "\n");
+	}
+	snd_printk(KERN_DEBUG "\n");
+	snd_printk(KERN_DEBUG "STAT: min_adds[]:\n");
+	for (j = 0; j < 8; j++) {
+		if (rec->min_adds[j] != 0)
+			snd_printk(KERN_DEBUG "%u: %u", j, rec->min_adds[j]);
+	}
+	snd_printk(KERN_DEBUG "\n");
+	snd_printk(KERN_DEBUG "STAT: mul_adds[]:\n");
+	for (j = 0; j < 8; j++) {
+		if (rec->mul_adds[j] != 0)
+			snd_printk(KERN_DEBUG "%u: %u", j, rec->mul_adds[j]);
+	}
+	snd_printk(KERN_DEBUG "\n");
+	snd_printk(KERN_DEBUG
+		   "STAT: zero_times_saved: %d, zero_times_notsaved: %d\n",
+		   rec->zero_times_saved, rec->zero_times_notsaved);
+	/* snd_printk(KERN_DEBUG "STAT: zero_times[]\n");
+	i = 0;
+	for (j = 0; j < 3750; j++) {
+		if (rec->zero_times[j] != 0) {
+			snd_printk(KERN_DEBUG "%u: %u", j, rec->zero_times[j]);
+			i++;
+		}
+		if (((i % 8) == 0) && (i != 0))
+			snd_printk(KERN_DEBUG "\n");
+	}
+	snd_printk(KERN_DEBUG "\n"); */
+	return;
+}
+#endif
+
+/*
+ * _internal_ helper function for playback/capture transfer function
+ */
+static void
+snd_pcm_indirect2_increase_min_periods(struct snd_pcm_substream *substream,
+				       struct snd_pcm_indirect2 *rec,
+				       int isplay, int iscopy,
+				       unsigned int bytes)
+{
+	if (rec->min_periods >= 0) {
+		if (iscopy) {
+			rec->sw_io += bytes;
+			if (rec->sw_io >= rec->sw_buffer_size)
+				rec->sw_io -= rec->sw_buffer_size;
+		} else if (isplay) {
+			/* If application does not write data in multiples of
+			 * a period, move sw_data to the next correctly aligned
+			 * position, so that sw_io can converge to it (in the
+			 * next step).
+			 */
+			if (!rec->check_alignment) {
+				if (rec->bytes2hw %
+				    snd_pcm_lib_period_bytes(substream)) {
+					unsigned bytes2hw_aligned =
+					    (1 +
+					     (rec->bytes2hw /
+					      snd_pcm_lib_period_bytes
+					      (substream))) *
+					    snd_pcm_lib_period_bytes
+					    (substream);
+					rec->sw_data =
+					    bytes2hw_aligned %
+					    rec->sw_buffer_size;
+#ifdef SND_PCM_INDIRECT2_STAT
+					snd_printk(KERN_DEBUG
+						   "STAT: @re-align: aligned "
+						   "bytes2hw to next period "
+						   "size boundary: %d "
+						   "(instead of %d)\n",
+						   bytes2hw_aligned,
+						   rec->bytes2hw);
+					snd_printk(KERN_DEBUG
+						   "STAT: @re-align: sw_data "
+						   "moves to: %d\n",
+						   rec->sw_data);
+#endif
+				}
+				rec->check_alignment = 1;
+			}
+			/* We are at the end and are copying zeros into the
+			 * fifo.
+			 * Now, we have to make sure that sw_io is increased
+			 * until the position of sw_data: Filling the fifo with
+			 * the first zeros means, the last bytes were played.
+			 */
+			if (rec->sw_io != rec->sw_data) {
+				unsigned int diff;
+				if (rec->sw_data > rec->sw_io)
+					diff = rec->sw_data - rec->sw_io;
+				else
+					diff = (rec->sw_buffer_size -
+						rec->sw_io) +
+						rec->sw_data;
+				if (bytes >= diff)
+					rec->sw_io = rec->sw_data;
+				else {
+					rec->sw_io += bytes;
+					if (rec->sw_io >= rec->sw_buffer_size)
+						rec->sw_io -=
+						    rec->sw_buffer_size;
+				}
+			}
+		}
+		rec->min_period_count += bytes;
+		if (rec->min_period_count >= (rec->hw_buffer_size / 2)) {
+			rec->min_periods += (rec->min_period_count /
+					     (rec->hw_buffer_size / 2));
+#ifdef SND_PCM_INDIRECT2_STAT
+			if ((rec->min_period_count /
+			     (rec->hw_buffer_size / 2)) > 7)
+				snd_printk(KERN_DEBUG
+					   "STAT: more than 7 (%d) min_adds "
+					   "at once - too big to save!\n",
+					   (rec->min_period_count /
+					    (rec->hw_buffer_size / 2)));
+			else
+				rec->min_adds[(rec->min_period_count /
+					       (rec->hw_buffer_size / 2))]++;
+#endif
+			rec->min_period_count = (rec->min_period_count %
+						 (rec->hw_buffer_size / 2));
+		}
+	} else if (isplay && iscopy)
+		rec->min_periods = 0;
+}
+
+/*
+ * helper function for playback/capture pointer callback
+ */
+snd_pcm_uframes_t
+snd_pcm_indirect2_pointer(struct snd_pcm_substream *substream,
+			  struct snd_pcm_indirect2 *rec)
+{
+#ifdef SND_PCM_INDIRECT2_STAT
+	rec->pointer_calls++;
+#endif
+	return bytes_to_frames(substream->runtime, rec->sw_io);
+}
+
+/*
+ * _internal_ helper function for playback interrupt callback
+ */
+static void
+snd_pcm_indirect2_playback_transfer(struct snd_pcm_substream *substream,
+				    struct snd_pcm_indirect2 *rec,
+				    snd_pcm_indirect2_copy_t copy,
+				    snd_pcm_indirect2_zero_t zero)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	snd_pcm_uframes_t appl_ptr = runtime->control->appl_ptr;
+
+	/* runtime->control->appl_ptr: position where ALSA will write next time
+	 * rec->appl_ptr: position where ALSA was last time
+	 * diff: obviously ALSA wrote that much bytes into the intermediate
+	 * buffer since we checked last time
+	 */
+	snd_pcm_sframes_t diff = appl_ptr - rec->appl_ptr;
+
+	if (diff) {
+#ifdef SND_PCM_INDIRECT2_STAT
+		rec->lastdifftime = jiffies;
+#endif
+		if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
+			diff += runtime->boundary;
+		/* number of bytes "added" by ALSA increases the number of
+		 * bytes which are ready to "be transfered to HW"/"played"
+		 * Then, set rec->appl_ptr to not count bytes twice next time.
+		 */
+		rec->sw_ready += (int)frames_to_bytes(runtime, diff);
+		rec->appl_ptr = appl_ptr;
+	}
+	if (rec->hw_ready && (rec->sw_ready <= 0)) {
+		unsigned int bytes;
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		if (rec->firstzerotime == 0) {
+			rec->firstzerotime = jiffies;
+			snd_printk(KERN_DEBUG
+				   "STAT: @firstzerotime: mul_elapsed: %d, "
+				   "min_period_count: %d\n",
+				   rec->mul_elapsed, rec->min_period_count);
+			snd_printk(KERN_DEBUG
+				   "STAT: @firstzerotime: sw_io: %d, "
+				   "sw_data: %d, appl_ptr: %u\n",
+				   rec->sw_io, rec->sw_data,
+				   (unsigned int)appl_ptr);
+		}
+		if ((jiffies - rec->firstzerotime) < 3750) {
+			rec->zero_times[(jiffies - rec->firstzerotime)]++;
+			rec->zero_times_saved++;
+		} else
+			rec->zero_times_notsaved++;
+#endif
+		bytes = zero(substream, rec);
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		rec->zeros2hw += bytes;
+		if (bytes < 64)
+			rec->zero_sizes[bytes]++;
+		else
+			snd_printk(KERN_DEBUG
+				   "STAT: %d zero Bytes copied to hardware at "
+				   "once - too big to save!\n",
+				   bytes);
+#endif
+		snd_pcm_indirect2_increase_min_periods(substream, rec, 1, 0,
+						       bytes);
+		return;
+	}
+	while (rec->hw_ready && (rec->sw_ready > 0)) {
+		/* sw_to_end: max. number of bytes that can be read/take from
+		 * the current position (sw_data) in _one_ step
+		 */
+		unsigned int sw_to_end = rec->sw_buffer_size - rec->sw_data;
+
+		/* bytes: number of bytes we have available (for reading) */
+		unsigned int bytes = rec->sw_ready;
+
+		if (sw_to_end < bytes)
+			bytes = sw_to_end;
+		if (!bytes)
+			break;
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		if (rec->firstbytetime == 0)
+			rec->firstbytetime = jiffies;
+		rec->lastbytetime = jiffies;
+#endif
+		/* copy bytes from intermediate buffer position sw_data to the
+		 * HW and return number of bytes actually written
+		 * Furthermore, set hw_ready to 0, if the fifo isn't empty
+		 * now => more could be transfered to fifo
+		 */
+		bytes = copy(substream, rec, bytes);
+		rec->bytes2hw += bytes;
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		if (bytes < 64)
+			rec->byte_sizes[bytes]++;
+		else
+			snd_printk(KERN_DEBUG
+				   "STAT: %d Bytes copied to hardware at once "
+				   "- too big to save!\n",
+				   bytes);
+#endif
+		/* increase sw_data by the number of actually written bytes
+		 * (= number of taken bytes from intermediate buffer)
+		 */
+		rec->sw_data += bytes;
+		if (rec->sw_data == rec->sw_buffer_size)
+			rec->sw_data = 0;
+		/* now sw_data is the position where ALSA is going to write
+		 * in the intermediate buffer next time = position we are going
+		 * to read from next time
+		 */
+
+		snd_pcm_indirect2_increase_min_periods(substream, rec, 1, 1,
+						       bytes);
+
+		/* we read bytes from intermediate buffer, so we need to say
+		 * that the number of bytes ready for transfer are decreased
+		 * now
+		 */
+		rec->sw_ready -= bytes;
+	}
+	return;
+}
+
+/*
+ * helper function for playback interrupt routine
+ */
+void
+snd_pcm_indirect2_playback_interrupt(struct snd_pcm_substream *substream,
+				     struct snd_pcm_indirect2 *rec,
+				     snd_pcm_indirect2_copy_t copy,
+				     snd_pcm_indirect2_zero_t zero)
+{
+#ifdef SND_PCM_INDIRECT2_STAT
+	rec->irq_occured++;
+#endif
+	/* hardware played some bytes, so there is room again (in fifo) */
+	rec->hw_ready = 1;
+
+	/* don't call ack() now, instead call transfer() function directly
+	 * (normally called by ack() )
+	 */
+	snd_pcm_indirect2_playback_transfer(substream, rec, copy, zero);
+
+	if (rec->min_periods >= rec->min_multiple) {
+#ifdef SND_PCM_INDIRECT2_STAT
+		if ((rec->min_periods / rec->min_multiple) > 7)
+			snd_printk(KERN_DEBUG
+				   "STAT: more than 7 (%d) mul_adds - too big "
+				   "to save!\n",
+				   (rec->min_periods / rec->min_multiple));
+		else
+			rec->mul_adds[(rec->min_periods /
+				       rec->min_multiple)]++;
+		rec->mul_elapsed_real += (rec->min_periods /
+					  rec->min_multiple);
+		rec->mul_elapsed++;
+#endif
+		rec->min_periods = 0;
+		snd_pcm_period_elapsed(substream);
+	}
+}
+
+/*
+ * _internal_ helper function for capture interrupt callback
+ */
+static void
+snd_pcm_indirect2_capture_transfer(struct snd_pcm_substream *substream,
+				   struct snd_pcm_indirect2 *rec,
+				   snd_pcm_indirect2_copy_t copy,
+				   snd_pcm_indirect2_zero_t null)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	snd_pcm_uframes_t appl_ptr = runtime->control->appl_ptr;
+	snd_pcm_sframes_t diff = appl_ptr - rec->appl_ptr;
+
+	if (diff) {
+#ifdef SND_PCM_INDIRECT2_STAT
+		rec->lastdifftime = jiffies;
+#endif
+		if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
+			diff += runtime->boundary;
+		rec->sw_ready -= frames_to_bytes(runtime, diff);
+		rec->appl_ptr = appl_ptr;
+	}
+	/* if hardware has something, but the intermediate buffer is full
+	 * => skip contents of buffer
+	 */
+	if (rec->hw_ready && (rec->sw_ready >= (int)rec->sw_buffer_size)) {
+		unsigned int bytes;
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		if (rec->firstzerotime == 0) {
+			rec->firstzerotime = jiffies;
+			snd_printk(KERN_DEBUG "STAT: (capture) "
+				   "@firstzerotime: mul_elapsed: %d, "
+				   "min_period_count: %d\n",
+				   rec->mul_elapsed, rec->min_period_count);
+			snd_printk(KERN_DEBUG "STAT: (capture) "
+				   "@firstzerotime: sw_io: %d, sw_data: %d, "
+				   "appl_ptr: %u\n",
+				   rec->sw_io, rec->sw_data,
+				   (unsigned int)appl_ptr);
+		}
+		if ((jiffies - rec->firstzerotime) < 3750) {
+			rec->zero_times[(jiffies - rec->firstzerotime)]++;
+			rec->zero_times_saved++;
+		} else
+			rec->zero_times_notsaved++;
+#endif
+		bytes = null(substream, rec);
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		rec->zeros2hw += bytes;
+		if (bytes < 64)
+			rec->zero_sizes[bytes]++;
+		else
+			snd_printk(KERN_DEBUG
+				   "STAT: (capture) %d zero Bytes copied to "
+				   "hardware at once - too big to save!\n",
+				   bytes);
+#endif
+		snd_pcm_indirect2_increase_min_periods(substream, rec, 0, 0,
+						       bytes);
+		/* report an overrun */
+		rec->sw_io = SNDRV_PCM_POS_XRUN;
+		return;
+	}
+	while (rec->hw_ready && (rec->sw_ready < (int)rec->sw_buffer_size)) {
+		/* sw_to_end: max. number of bytes that we can write to the
+		 *  intermediate buffer (until it's end)
+		 */
+		size_t sw_to_end = rec->sw_buffer_size - rec->sw_data;
+
+		/* bytes: max. number of bytes, which may be copied to the
+		 *  intermediate buffer without overflow (in _one_ step)
+		 */
+		size_t bytes = rec->sw_buffer_size - rec->sw_ready;
+
+		/* limit number of bytes (for transfer) by available room in
+		 * the intermediate buffer
+		 */
+		if (sw_to_end < bytes)
+			bytes = sw_to_end;
+		if (!bytes)
+			break;
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		if (rec->firstbytetime == 0)
+			rec->firstbytetime = jiffies;
+		rec->lastbytetime = jiffies;
+#endif
+		/* copy bytes from the intermediate buffer (position sw_data)
+		 * to the HW at most and return number of bytes actually copied
+		 * from HW
+		 * Furthermore, set hw_ready to 0, if the fifo is empty now.
+		 */
+		bytes = copy(substream, rec, bytes);
+		rec->bytes2hw += bytes;
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		if (bytes < 64)
+			rec->byte_sizes[bytes]++;
+		else
+			snd_printk(KERN_DEBUG
+				   "STAT: (capture) %d Bytes copied to "
+				   "hardware at once - too big to save!\n",
+				   bytes);
+#endif
+		/* increase sw_data by the number of actually copied bytes from
+		 * HW
+		 */
+		rec->sw_data += bytes;
+		if (rec->sw_data == rec->sw_buffer_size)
+			rec->sw_data = 0;
+
+		snd_pcm_indirect2_increase_min_periods(substream, rec, 0, 1,
+						       bytes);
+
+		/* number of bytes in the intermediate buffer, which haven't
+		 * been fetched by ALSA yet.
+		 */
+		rec->sw_ready += bytes;
+	}
+	return;
+}
+
+/*
+ * helper function for capture interrupt routine
+ */
+void
+snd_pcm_indirect2_capture_interrupt(struct snd_pcm_substream *substream,
+				    struct snd_pcm_indirect2 *rec,
+				    snd_pcm_indirect2_copy_t copy,
+				    snd_pcm_indirect2_zero_t null)
+{
+#ifdef SND_PCM_INDIRECT2_STAT
+	rec->irq_occured++;
+#endif
+	/* hardware recorded some bytes, so there is something to read from the
+	 * record fifo:
+	 */
+	rec->hw_ready = 1;
+
+	/* don't call ack() now, instead call transfer() function directly
+	 * (normally called by ack() )
+	 */
+	snd_pcm_indirect2_capture_transfer(substream, rec, copy, null);
+
+	if (rec->min_periods >= rec->min_multiple) {
+
+#ifdef SND_PCM_INDIRECT2_STAT
+		if ((rec->min_periods / rec->min_multiple) > 7)
+			snd_printk(KERN_DEBUG
+				   "STAT: more than 7 (%d) mul_adds - "
+				   "too big to save!\n",
+				   (rec->min_periods / rec->min_multiple));
+		else
+			rec->mul_adds[(rec->min_periods /
+				       rec->min_multiple)]++;
+		rec->mul_elapsed_real += (rec->min_periods /
+					  rec->min_multiple);
+		rec->mul_elapsed++;
+
+		if (!(rec->mul_elapsed % 4)) {
+			struct snd_pcm_runtime *runtime = substream->runtime;
+			unsigned int appl_ptr =
+			    frames_to_bytes(runtime,
+					    (unsigned int)runtime->control->
+					    appl_ptr) % rec->sw_buffer_size;
+			int diff = rec->sw_data - appl_ptr;
+			if (diff < 0)
+				diff += rec->sw_buffer_size;
+			snd_printk(KERN_DEBUG
+				   "STAT: mul_elapsed: %d, sw_data: %u, "
+				   "appl_ptr (bytes): %u, diff: %d\n",
+				   rec->mul_elapsed, rec->sw_data, appl_ptr,
+				   diff);
+		}
+#endif
+		rec->min_periods = 0;
+		snd_pcm_period_elapsed(substream);
+	}
+}

sound/drivers/pcm-indirect2.h

+/*
+ * Helper functions for indirect PCM data transfer to a simple FIFO in
+ * hardware (small, no possibility to read "hardware io position",
+ * updating position done by interrupt, ...)
+ *
+ *  Copyright (c) by 2007  Joachim Foerster <JOFT@gmx.de>
+ *
+ *  Based on "pcm-indirect.h" (alsa-driver-1.0.13) by
+ *
+ *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
+ *                   Jaroslav Kysela <perex@suse.cz>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef __SOUND_PCM_INDIRECT2_H
+#define __SOUND_PCM_INDIRECT2_H
+
+/* struct snd_pcm_substream, struct snd_pcm_runtime, snd_pcm_uframes_t */
+#include <sound/pcm.h>
+
+/* Debug options for code which may be removed completely in a final version */
+#ifdef CONFIG_SND_DEBUG
+#define SND_PCM_INDIRECT2_STAT    /* turn on some "statistics" about the
+				   * process of copying bytes from the
+				   * intermediate buffer to the hardware
+				   * fifo and the other way round
+				   */
+#endif
+
+struct snd_pcm_indirect2 {
+	unsigned int hw_buffer_size;  /* Byte size of hardware buffer */
+	int hw_ready;		      /* playback: 1 = hw fifo has room left,
+				       * 0 = hw fifo is full
+				       */
+	unsigned int min_multiple;
+	int min_periods;	      /* counts number of min. periods until
+				       * min_multiple is reached
+				       */
+	int min_period_count;	      /* counts bytes to count number of
+				       * min. periods
+				       */
+
+	unsigned int sw_buffer_size;  /* Byte size of software buffer */
+
+	/* sw_data: position in intermediate buffer, where we will read (or
+	 *          write) from/to next time (to transfer data to/from HW)
+	 */
+	unsigned int sw_data;         /* Offset to next dst (or src) in sw
+				       * ring buffer
+				       */
+	/* easiest case (playback):
+	 * sw_data is nearly the same as ~ runtime->control->appl_ptr, with the
+	 * exception that sw_data is "behind" by the number if bytes ALSA wrote
+	 * to the intermediate buffer last time.
+	 * A call to ack() callback synchronizes both indirectly.
+	 */
+
+	/* We have no real sw_io pointer here. Usually sw_io is pointing to the
+	 * current playback/capture position _inside_ the hardware. Devices
+	 * with plain FIFOs often have no possibility to publish this position.
+	 * So we say: if sw_data is updated, that means bytes were copied to
+	 * the hardware, we increase sw_io by that amount, because there have
+	 * to be as much bytes which were played. So sw_io will stay behind
+	 * sw_data all the time and has to converge to sw_data at the end of
+	 * playback.
+	 */
+	unsigned int sw_io;           /* Current software pointer in bytes */
+
+	/* sw_ready: number of bytes ALSA copied to the intermediate buffer, so
+	 * it represents the number of bytes which wait for transfer to the HW
+	 */
+	int sw_ready;		  /* Bytes ready to be transferred to/from hw */
+
+	/* appl_ptr: last known position of ALSA (where ALSA is going to write
+	 * next time into the intermediate buffer
+	 */
+	snd_pcm_uframes_t appl_ptr;   /* Last seen appl_ptr */
+
+	unsigned int bytes2hw;
+	int check_alignment;
+
+#ifdef SND_PCM_INDIRECT2_STAT
+	unsigned int zeros2hw;
+	unsigned int mul_elapsed;
+	unsigned int mul_elapsed_real;
+	unsigned long firstbytetime;
+	unsigned long lastbytetime;
+	unsigned long firstzerotime;
+	unsigned int byte_sizes[64];
+	unsigned int zero_sizes[64];
+	unsigned int min_adds[8];
+	unsigned int mul_adds[8];
+	unsigned int zero_times[3750];	/* = 15s */
+	unsigned int zero_times_saved;
+	unsigned int zero_times_notsaved;
+	unsigned int irq_occured;
+	unsigned int pointer_calls;
+	unsigned int lastdifftime;
+#endif
+};
+
+typedef size_t (*snd_pcm_indirect2_copy_t) (struct snd_pcm_substream *substream,
+					   struct snd_pcm_indirect2 *rec,
+					   size_t bytes);
+typedef size_t (*snd_pcm_indirect2_zero_t) (struct snd_pcm_substream *substream,
+					   struct snd_pcm_indirect2 *rec);
+
+#ifdef SND_PCM_INDIRECT2_STAT
+void snd_pcm_indirect2_stat(struct snd_pcm_substream *substream,
+				   struct snd_pcm_indirect2 *rec);
+#endif
+
+snd_pcm_uframes_t
+snd_pcm_indirect2_pointer(struct snd_pcm_substream *substream,
+			  struct snd_pcm_indirect2 *rec);
+void
+snd_pcm_indirect2_playback_interrupt(struct snd_pcm_substream *substream,
+				     struct snd_pcm_indirect2 *rec,
+				     snd_pcm_indirect2_copy_t copy,
+				     snd_pcm_indirect2_zero_t zero);
+void
+snd_pcm_indirect2_capture_interrupt(struct snd_pcm_substream *substream,
+				    struct snd_pcm_indirect2 *rec,
+				    snd_pcm_indirect2_copy_t copy,
+				    snd_pcm_indirect2_zero_t null);
+
+#endif /* __SOUND_PCM_INDIRECT2_H */