950-0078-Support-for-Blokas-Labs-pisound-board.patch

From 85ef9efcc598bff1d783620e23c09aed873e7aee Mon Sep 17 00:00:00 2001
From: gtrainavicius <gtrainavicius@users.noreply.github.com>
Date: Sun, 23 Oct 2016 12:06:53 +0300
Subject: [PATCH] Support for Blokas Labs pisound board

Pisound dynamic overlay (#1760)

Restructuring pisound-overlay.dts, so it can be loaded and unloaded dynamically using dtoverlay.

Print a logline when the kernel module is removed.

pisound improvements:

* Added a writable sysfs object to enable scripts / user space software
to blink MIDI activity LEDs for variable duration.
* Improved hw_param constraints setting.
* Added compatibility with S16_LE sample format.
* Exposed some simple placeholder volume controls, so the card appears
in volumealsa widget.

Add missing SND_PISOUND selects dependency to SND_RAWMIDI

Without it the Pisound module fails to compile.
See https://github.com/raspberrypi/linux/issues/2366

Updates for Pisound module code:

	* Merged 'Fix a warning in DEBUG builds' (1c8b82b).
	* Updating some strings and copyright information.
	* Fix for handling high load of MIDI input and output.
	* Use dual rate oversampling ratio for 96kHz instead of single
	  rate one.

Signed-off-by: Giedrius Trainavicius <giedrius@blokas.io>

Fixing memset call in pisound.c

Signed-off-by: Giedrius Trainavicius <giedrius@blokas.io>

Fix for Pisound's MIDI Input getting blocked for a while in rare cases.

There was a possible race condition which could lead to Input's FIFO queue
to be underflown, causing high amount of processing in the worker thread for
some period of time.

Signed-off-by: Giedrius Trainavicius <giedrius@blokas.io>
---
 .../devicetree/bindings/vendor-prefixes.txt   |    1 +
 sound/soc/bcm/pisound.c                       | 1204 +++++++++++++++++
 2 files changed, 1205 insertions(+)
 create mode 100644 sound/soc/bcm/pisound.c

--- a/Documentation/devicetree/bindings/vendor-prefixes.txt
+++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
@@ -56,6 +56,7 @@ axis	Axis Communications AB
 bananapi BIPAI KEJI LIMITED
 bhf	Beckhoff Automation GmbH & Co. KG
 bitmain	Bitmain Technologies
+blokaslabs	Vilniaus Blokas UAB
 boe	BOE Technology Group Co., Ltd.
 bosch	Bosch Sensortec GmbH
 boundary	Boundary Devices Inc.
--- /dev/null
+++ b/sound/soc/bcm/pisound.c
@@ -0,0 +1,1204 @@
+/*
+ * Pisound Linux kernel module.
+ * Copyright (C) 2016-2017  Vilniaus Blokas UAB, https://blokas.io/pisound
+ *
+ * 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; version 2 of the
+ * License.
+ *
+ * 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., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301, USA.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/gpio.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+#include <linux/delay.h>
+#include <linux/spi/spi.h>
+#include <linux/interrupt.h>
+#include <linux/kfifo.h>
+#include <linux/jiffies.h>
+
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+#include <sound/soc.h>
+#include <sound/jack.h>
+#include <sound/rawmidi.h>
+#include <sound/asequencer.h>
+#include <sound/control.h>
+
+static int pisnd_spi_init(struct device *dev);
+static void pisnd_spi_uninit(void);
+
+static void pisnd_spi_flush(void);
+static void pisnd_spi_start(void);
+static uint8_t pisnd_spi_recv(uint8_t *buffer, uint8_t length);
+
+typedef void (*pisnd_spi_recv_cb)(void *data);
+static void pisnd_spi_set_callback(pisnd_spi_recv_cb cb, void *data);
+
+static const char *pisnd_spi_get_serial(void);
+static const char *pisnd_spi_get_id(void);
+static const char *pisnd_spi_get_version(void);
+
+static int pisnd_midi_init(struct snd_card *card);
+static void pisnd_midi_uninit(void);
+
+enum task_e {
+	TASK_PROCESS = 0,
+};
+
+static void pisnd_schedule_process(enum task_e task);
+
+#define PISOUND_LOG_PREFIX "pisound: "
+
+#ifdef PISOUND_DEBUG
+#	define printd(...) pr_alert(PISOUND_LOG_PREFIX __VA_ARGS__)
+#else
+#	define printd(...) do {} while (0)
+#endif
+
+#define printe(...) pr_err(PISOUND_LOG_PREFIX __VA_ARGS__)
+#define printi(...) pr_info(PISOUND_LOG_PREFIX __VA_ARGS__)
+
+static struct snd_rawmidi *g_rmidi;
+static struct snd_rawmidi_substream *g_midi_output_substream;
+
+static int pisnd_output_open(struct snd_rawmidi_substream *substream)
+{
+	g_midi_output_substream = substream;
+	return 0;
+}
+
+static int pisnd_output_close(struct snd_rawmidi_substream *substream)
+{
+	g_midi_output_substream = NULL;
+	return 0;
+}
+
+static void pisnd_output_trigger(
+	struct snd_rawmidi_substream *substream,
+	int up
+	)
+{
+	if (substream != g_midi_output_substream) {
+		printe("MIDI output trigger called for an unexpected stream!");
+		return;
+	}
+
+	if (!up)
+		return;
+
+	pisnd_spi_start();
+}
+
+static void pisnd_output_drain(struct snd_rawmidi_substream *substream)
+{
+	pisnd_spi_flush();
+}
+
+static int pisnd_input_open(struct snd_rawmidi_substream *substream)
+{
+	return 0;
+}
+
+static int pisnd_input_close(struct snd_rawmidi_substream *substream)
+{
+	return 0;
+}
+
+static void pisnd_midi_recv_callback(void *substream)
+{
+	uint8_t data[128];
+	uint8_t n = 0;
+
+	while ((n = pisnd_spi_recv(data, sizeof(data)))) {
+		int res = snd_rawmidi_receive(substream, data, n);
+		(void)res;
+		printd("midi recv %u bytes, res = %d\n", n, res);
+	}
+}
+
+static void pisnd_input_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+	if (up) {
+		pisnd_spi_set_callback(pisnd_midi_recv_callback, substream);
+		pisnd_schedule_process(TASK_PROCESS);
+	} else {
+		pisnd_spi_set_callback(NULL, NULL);
+	}
+}
+
+static struct snd_rawmidi_ops pisnd_output_ops = {
+	.open = pisnd_output_open,
+	.close = pisnd_output_close,
+	.trigger = pisnd_output_trigger,
+	.drain = pisnd_output_drain,
+};
+
+static struct snd_rawmidi_ops pisnd_input_ops = {
+	.open = pisnd_input_open,
+	.close = pisnd_input_close,
+	.trigger = pisnd_input_trigger,
+};
+
+static void pisnd_get_port_info(
+	struct snd_rawmidi *rmidi,
+	int number,
+	struct snd_seq_port_info *seq_port_info
+	)
+{
+	seq_port_info->type =
+		SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC |
+		SNDRV_SEQ_PORT_TYPE_HARDWARE |
+		SNDRV_SEQ_PORT_TYPE_PORT;
+	seq_port_info->midi_voices = 0;
+}
+
+static struct snd_rawmidi_global_ops pisnd_global_ops = {
+	.get_port_info = pisnd_get_port_info,
+};
+
+static int pisnd_midi_init(struct snd_card *card)
+{
+	int err;
+
+	g_midi_output_substream = NULL;
+
+	err = snd_rawmidi_new(card, "pisound MIDI", 0, 1, 1, &g_rmidi);
+
+	if (err < 0) {
+		printe("snd_rawmidi_new failed: %d\n", err);
+		return err;
+	}
+
+	strcpy(g_rmidi->name, "pisound MIDI ");
+	strcat(g_rmidi->name, pisnd_spi_get_serial());
+
+	g_rmidi->info_flags =
+		SNDRV_RAWMIDI_INFO_OUTPUT |
+		SNDRV_RAWMIDI_INFO_INPUT |
+		SNDRV_RAWMIDI_INFO_DUPLEX;
+
+	g_rmidi->ops = &pisnd_global_ops;
+
+	g_rmidi->private_data = (void *)0;
+
+	snd_rawmidi_set_ops(
+		g_rmidi,
+		SNDRV_RAWMIDI_STREAM_OUTPUT,
+		&pisnd_output_ops
+		);
+
+	snd_rawmidi_set_ops(
+		g_rmidi,
+		SNDRV_RAWMIDI_STREAM_INPUT,
+		&pisnd_input_ops
+		);
+
+	return 0;
+}
+
+static void pisnd_midi_uninit(void)
+{
+}
+
+static void *g_recvData;
+static pisnd_spi_recv_cb g_recvCallback;
+
+#define FIFO_SIZE 4096
+
+static char g_serial_num[11];
+static char g_id[25];
+static char g_version[5];
+
+static uint8_t g_ledFlashDuration;
+static bool    g_ledFlashDurationChanged;
+
+DEFINE_KFIFO(spi_fifo_in,  uint8_t, FIFO_SIZE);
+DEFINE_KFIFO(spi_fifo_out, uint8_t, FIFO_SIZE);
+
+static struct gpio_desc *data_available;
+static struct gpio_desc *spi_reset;
+
+static struct spi_device *pisnd_spi_device;
+
+static struct workqueue_struct *pisnd_workqueue;
+static struct work_struct pisnd_work_process;
+
+static void pisnd_work_handler(struct work_struct *work);
+
+static void spi_transfer(const uint8_t *txbuf, uint8_t *rxbuf, int len);
+static uint16_t spi_transfer16(uint16_t val);
+
+static int pisnd_init_workqueues(void)
+{
+	pisnd_workqueue = create_singlethread_workqueue("pisnd_workqueue");
+	INIT_WORK(&pisnd_work_process, pisnd_work_handler);
+
+	return 0;
+}
+
+static void pisnd_uninit_workqueues(void)
+{
+	flush_workqueue(pisnd_workqueue);
+	destroy_workqueue(pisnd_workqueue);
+
+	pisnd_workqueue = NULL;
+}
+
+static bool pisnd_spi_has_more(void)
+{
+	return gpiod_get_value(data_available);
+}
+
+static void pisnd_schedule_process(enum task_e task)
+{
+	if (pisnd_spi_device != NULL &&
+		pisnd_workqueue != NULL &&
+		!work_pending(&pisnd_work_process)
+		) {
+		printd("schedule: has more = %d\n", pisnd_spi_has_more());
+		if (task == TASK_PROCESS)
+			queue_work(pisnd_workqueue, &pisnd_work_process);
+	}
+}
+
+static irqreturn_t data_available_interrupt_handler(int irq, void *dev_id)
+{
+	if (irq == gpiod_to_irq(data_available) && pisnd_spi_has_more()) {
+		printd("schedule from irq\n");
+		pisnd_schedule_process(TASK_PROCESS);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static DEFINE_SPINLOCK(spilock);
+static unsigned long spilockflags;
+
+static uint16_t spi_transfer16(uint16_t val)
+{
+	uint8_t txbuf[2];
+	uint8_t rxbuf[2];
+
+	if (!pisnd_spi_device) {
+		printe("pisnd_spi_device null, returning\n");
+		return 0;
+	}
+
+	txbuf[0] = val >> 8;
+	txbuf[1] = val & 0xff;
+
+	spi_transfer(txbuf, rxbuf, sizeof(txbuf));
+
+	printd("received: %02x%02x\n", rxbuf[0], rxbuf[1]);
+
+	return (rxbuf[0] << 8) | rxbuf[1];
+}
+
+static void spi_transfer(const uint8_t *txbuf, uint8_t *rxbuf, int len)
+{
+	int err;
+	struct spi_transfer transfer;
+	struct spi_message msg;
+
+	memset(rxbuf, 0, len);
+
+	if (!pisnd_spi_device) {
+		printe("pisnd_spi_device null, returning\n");
+		return;
+	}
+
+	spi_message_init(&msg);
+
+	memset(&transfer, 0, sizeof(transfer));
+
+	transfer.tx_buf = txbuf;
+	transfer.rx_buf = rxbuf;
+	transfer.len = len;
+	transfer.speed_hz = 100000;
+	transfer.delay_usecs = 10;
+	spi_message_add_tail(&transfer, &msg);
+
+	spin_lock_irqsave(&spilock, spilockflags);
+	err = spi_sync(pisnd_spi_device, &msg);
+	spin_unlock_irqrestore(&spilock, spilockflags);
+
+	if (err < 0) {
+		printe("spi_sync error %d\n", err);
+		return;
+	}
+
+	printd("hasMore %d\n", pisnd_spi_has_more());
+}
+
+static int spi_read_bytes(char *dst, size_t length, uint8_t *bytesRead)
+{
+	uint16_t rx;
+	uint8_t size;
+	uint8_t i;
+
+	memset(dst, 0, length);
+	*bytesRead = 0;
+
+	rx = spi_transfer16(0);
+	if (!(rx >> 8))
+		return -EINVAL;
+
+	size = rx & 0xff;
+
+	if (size > length)
+		return -EINVAL;
+
+	for (i = 0; i < size; ++i) {
+		rx = spi_transfer16(0);
+		if (!(rx >> 8))
+			return -EINVAL;
+
+		dst[i] = rx & 0xff;
+	}
+
+	*bytesRead = i;
+
+	return 0;
+}
+
+static int spi_device_match(struct device *dev, void *data)
+{
+	struct spi_device *spi = container_of(dev, struct spi_device, dev);
+
+	printd("      %s %s %dkHz %d bits mode=0x%02X\n",
+		spi->modalias, dev_name(dev), spi->max_speed_hz/1000,
+		spi->bits_per_word, spi->mode);
+
+	if (strcmp("pisound-spi", spi->modalias) == 0) {
+		printi("\tFound!\n");
+		return 1;
+	}
+
+	printe("\tNot found!\n");
+	return 0;
+}
+
+static struct spi_device *pisnd_spi_find_device(void)
+{
+	struct device *dev;
+
+	printi("Searching for spi device...\n");
+	dev = bus_find_device(&spi_bus_type, NULL, NULL, spi_device_match);
+	if (dev != NULL)
+		return container_of(dev, struct spi_device, dev);
+	else
+		return NULL;
+}
+
+static void pisnd_work_handler(struct work_struct *work)
+{
+	enum { TRANSFER_SIZE = 4 };
+	enum { PISOUND_OUTPUT_BUFFER_SIZE = 128 };
+	enum { MIDI_BYTES_PER_SECOND = 3125 };
+	int out_buffer_used = 0;
+	unsigned long now;
+	uint8_t val;
+	uint8_t txbuf[TRANSFER_SIZE];
+	uint8_t rxbuf[TRANSFER_SIZE];
+	uint8_t midibuf[TRANSFER_SIZE];
+	int i, n;
+	bool had_data;
+
+	unsigned long last_transfer_at = jiffies;
+
+	if (work == &pisnd_work_process) {
+		if (pisnd_spi_device == NULL)
+			return;
+
+		do {
+			if (g_midi_output_substream &&
+				kfifo_avail(&spi_fifo_out) >= sizeof(midibuf)) {
+
+				n = snd_rawmidi_transmit_peek(
+					g_midi_output_substream,
+					midibuf, sizeof(midibuf)
+				);
+
+				if (n > 0) {
+					for (i = 0; i < n; ++i)
+						kfifo_put(
+							&spi_fifo_out,
+							midibuf[i]
+							);
+					snd_rawmidi_transmit_ack(
+						g_midi_output_substream,
+						i
+						);
+				}
+			}
+
+			had_data = false;
+			memset(txbuf, 0, sizeof(txbuf));
+			for (i = 0; i < sizeof(txbuf) &&
+				out_buffer_used < PISOUND_OUTPUT_BUFFER_SIZE;
+				i += 2) {
+
+				val = 0;
+
+				if (g_ledFlashDurationChanged) {
+					txbuf[i+0] = 0xf0;
+					txbuf[i+1] = g_ledFlashDuration;
+					g_ledFlashDuration = 0;
+					g_ledFlashDurationChanged = false;
+				} else if (kfifo_get(&spi_fifo_out, &val)) {
+					txbuf[i+0] = 0x0f;
+					txbuf[i+1] = val;
+					++out_buffer_used;
+				}
+			}
+
+			spi_transfer(txbuf, rxbuf, sizeof(txbuf));
+			/* Estimate the Pisound's MIDI output buffer usage, so
+			 * that we don't overflow it. Space in the buffer should
+			 * be becoming available at the UART MIDI byte transfer
+			 * rate.
+			 */
+			now = jiffies;
+			out_buffer_used -=
+				(MIDI_BYTES_PER_SECOND / HZ) /
+				(now - last_transfer_at);
+			if (out_buffer_used < 0)
+				out_buffer_used = 0;
+			last_transfer_at = now;
+
+			for (i = 0; i < sizeof(rxbuf); i += 2) {
+				if (rxbuf[i]) {
+					kfifo_put(&spi_fifo_in, rxbuf[i+1]);
+					if (kfifo_len(&spi_fifo_in) > 16 &&
+						g_recvCallback)
+						g_recvCallback(g_recvData);
+					had_data = true;
+				}
+			}
+		} while (had_data
+			|| !kfifo_is_empty(&spi_fifo_out)
+			|| pisnd_spi_has_more()
+			|| g_ledFlashDurationChanged
+			);
+
+		if (!kfifo_is_empty(&spi_fifo_in) && g_recvCallback)
+			g_recvCallback(g_recvData);
+	}
+}
+
+static int pisnd_spi_gpio_init(struct device *dev)
+{
+	spi_reset = gpiod_get_index(dev, "reset", 1, GPIOD_ASIS);
+	data_available = gpiod_get_index(dev, "data_available", 0, GPIOD_ASIS);
+
+	gpiod_direction_output(spi_reset, 1);
+	gpiod_direction_input(data_available);
+
+	/* Reset the slave. */
+	gpiod_set_value(spi_reset, false);
+	mdelay(1);
+	gpiod_set_value(spi_reset, true);
+
+	/* Give time for spi slave to start. */
+	mdelay(64);
+
+	return 0;
+}
+
+static void pisnd_spi_gpio_uninit(void)
+{
+	gpiod_set_value(spi_reset, false);
+	gpiod_put(spi_reset);
+	spi_reset = NULL;
+
+	gpiod_put(data_available);
+	data_available = NULL;
+}
+
+static int pisnd_spi_gpio_irq_init(struct device *dev)
+{
+	return request_irq(
+		gpiod_to_irq(data_available),
+		data_available_interrupt_handler,
+		IRQF_TIMER | IRQF_TRIGGER_RISING,
+		"data_available_int",
+		NULL
+		);
+}
+
+static void pisnd_spi_gpio_irq_uninit(void)
+{
+	free_irq(gpiod_to_irq(data_available), NULL);
+}
+
+static int spi_read_info(void)
+{
+	uint16_t tmp;
+	uint8_t count;
+	uint8_t n;
+	uint8_t i;
+	uint8_t j;
+	char buffer[257];
+	int ret;
+	char *p;
+
+	memset(g_serial_num, 0, sizeof(g_serial_num));
+	memset(g_version, 0, sizeof(g_version));
+	memset(g_id, 0, sizeof(g_id));
+
+	tmp = spi_transfer16(0);
+
+	if (!(tmp >> 8))
+		return -EINVAL;
+
+	count = tmp & 0xff;
+
+	for (i = 0; i < count; ++i) {
+		memset(buffer, 0, sizeof(buffer));
+		ret = spi_read_bytes(buffer, sizeof(buffer)-1, &n);
+
+		if (ret < 0)
+			return ret;
+
+		switch (i) {
+		case 0:
+			if (n != 2)
+				return -EINVAL;
+
+			snprintf(
+				g_version,
+				sizeof(g_version),
+				"%x.%02x",
+				buffer[0],
+				buffer[1]
+				);
+			break;
+		case 1:
+			if (n >= sizeof(g_serial_num))
+				return -EINVAL;
+
+			memcpy(g_serial_num, buffer, sizeof(g_serial_num));
+			break;
+		case 2:
+			{
+				if (n >= sizeof(g_id))
+					return -EINVAL;
+
+				p = g_id;
+				for (j = 0; j < n; ++j)
+					p += sprintf(p, "%02x", buffer[j]);
+			}
+			break;
+		default:
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static int pisnd_spi_init(struct device *dev)
+{
+	int ret;
+	struct spi_device *spi;
+
+	memset(g_serial_num, 0, sizeof(g_serial_num));
+	memset(g_id, 0, sizeof(g_id));
+	memset(g_version, 0, sizeof(g_version));
+
+	spi = pisnd_spi_find_device();
+
+	if (spi != NULL) {
+		printd("initializing spi!\n");
+		pisnd_spi_device = spi;
+		ret = spi_setup(pisnd_spi_device);
+	} else {
+		printe("SPI device not found, deferring!\n");
+		return -EPROBE_DEFER;
+	}
+
+	ret = pisnd_spi_gpio_init(dev);
+
+	if (ret < 0) {
+		printe("SPI GPIO init failed: %d\n", ret);
+		spi_dev_put(pisnd_spi_device);
+		pisnd_spi_device = NULL;
+		pisnd_spi_gpio_uninit();
+		return ret;
+	}
+
+	ret = spi_read_info();
+
+	if (ret < 0) {
+		printe("Reading card info failed: %d\n", ret);
+		spi_dev_put(pisnd_spi_device);
+		pisnd_spi_device = NULL;
+		pisnd_spi_gpio_uninit();
+		return ret;
+	}
+
+	/* Flash the LEDs. */
+	spi_transfer16(0xf008);
+
+	ret = pisnd_spi_gpio_irq_init(dev);
+	if (ret < 0) {
+		printe("SPI irq request failed: %d\n", ret);
+		spi_dev_put(pisnd_spi_device);
+		pisnd_spi_device = NULL;
+		pisnd_spi_gpio_irq_uninit();
+		pisnd_spi_gpio_uninit();
+	}
+
+	ret = pisnd_init_workqueues();
+	if (ret != 0) {
+		printe("Workqueue initialization failed: %d\n", ret);
+		spi_dev_put(pisnd_spi_device);
+		pisnd_spi_device = NULL;
+		pisnd_spi_gpio_irq_uninit();
+		pisnd_spi_gpio_uninit();
+		pisnd_uninit_workqueues();
+		return ret;
+	}
+
+	if (pisnd_spi_has_more()) {
+		printd("data is available, scheduling from init\n");
+		pisnd_schedule_process(TASK_PROCESS);
+	}
+
+	return 0;
+}
+
+static void pisnd_spi_uninit(void)
+{
+	pisnd_uninit_workqueues();
+
+	spi_dev_put(pisnd_spi_device);
+	pisnd_spi_device = NULL;
+
+	pisnd_spi_gpio_irq_uninit();
+	pisnd_spi_gpio_uninit();
+}
+
+static void pisnd_spi_flash_leds(uint8_t duration)
+{
+	g_ledFlashDuration = duration;
+	g_ledFlashDurationChanged = true;
+	printd("schedule from spi_flash_leds\n");
+	pisnd_schedule_process(TASK_PROCESS);
+}
+
+static void pisnd_spi_flush(void)
+{
+	while (!kfifo_is_empty(&spi_fifo_out)) {
+		pisnd_spi_start();
+		flush_workqueue(pisnd_workqueue);
+	}
+}
+
+static void pisnd_spi_start(void)
+{
+	printd("schedule from spi_start\n");
+	pisnd_schedule_process(TASK_PROCESS);
+}
+
+static uint8_t pisnd_spi_recv(uint8_t *buffer, uint8_t length)
+{
+	return kfifo_out(&spi_fifo_in, buffer, length);
+}
+
+static void pisnd_spi_set_callback(pisnd_spi_recv_cb cb, void *data)
+{
+	g_recvData = data;
+	g_recvCallback = cb;
+}
+
+static const char *pisnd_spi_get_serial(void)
+{
+	if (strlen(g_serial_num))
+		return g_serial_num;
+
+	return "";
+}
+
+static const char *pisnd_spi_get_id(void)
+{
+	if (strlen(g_id))
+		return g_id;
+
+	return "";
+}
+
+static const char *pisnd_spi_get_version(void)
+{
+	if (strlen(g_version))
+		return g_version;
+
+	return "";
+}
+
+static const struct of_device_id pisound_of_match[] = {
+	{ .compatible = "blokaslabs,pisound", },
+	{ .compatible = "blokaslabs,pisound-spi", },
+	{},
+};
+
+enum {
+	SWITCH = 0,
+	VOLUME = 1,
+};
+
+static int pisnd_ctl_info(struct snd_kcontrol *kcontrol,
+	struct snd_ctl_elem_info *uinfo)
+{
+	if (kcontrol->private_value == SWITCH) {
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+		uinfo->count = 1;
+		uinfo->value.integer.min = 0;
+		uinfo->value.integer.max = 1;
+		return 0;
+	} else if (kcontrol->private_value == VOLUME) {
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+		uinfo->count = 1;
+		uinfo->value.integer.min = 0;
+		uinfo->value.integer.max = 100;
+		return 0;
+	}
+	return -EINVAL;
+}
+
+static int pisnd_ctl_get(struct snd_kcontrol *kcontrol,
+	struct snd_ctl_elem_value *ucontrol)
+{
+	if (kcontrol->private_value == SWITCH) {
+		ucontrol->value.integer.value[0] = 1;
+		return 0;
+	} else if (kcontrol->private_value == VOLUME) {
+		ucontrol->value.integer.value[0] = 100;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static struct snd_kcontrol_new pisnd_ctl[] = {
+	{
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "PCM Playback Switch",
+		.index = 0,
+		.private_value = SWITCH,
+		.access = SNDRV_CTL_ELEM_ACCESS_READ,
+		.info = pisnd_ctl_info,
+		.get = pisnd_ctl_get,
+	},
+	{
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.name = "PCM Playback Volume",
+		.index = 0,
+		.private_value = VOLUME,
+		.access = SNDRV_CTL_ELEM_ACCESS_READ,
+		.info = pisnd_ctl_info,
+		.get = pisnd_ctl_get,
+	},
+};
+
+static int pisnd_ctl_init(struct snd_card *card)
+{
+	int err, i;
+
+	for (i = 0; i < ARRAY_SIZE(pisnd_ctl); ++i) {
+		err = snd_ctl_add(card, snd_ctl_new1(&pisnd_ctl[i], NULL));
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+static int pisnd_ctl_uninit(void)
+{
+	return 0;
+}
+
+static struct gpio_desc *osr0, *osr1, *osr2;
+static struct gpio_desc *reset;
+static struct gpio_desc *button;
+
+static int pisnd_hw_params(
+	struct snd_pcm_substream *substream,
+	struct snd_pcm_hw_params *params
+	)
+{
+	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
+
+	/* Pisound runs on fixed 32 clock counts per channel,
+	 * as generated by the master ADC.
+	 */
+	snd_soc_dai_set_bclk_ratio(cpu_dai, 32*2);
+
+	printd("rate   = %d\n", params_rate(params));
+	printd("ch     = %d\n", params_channels(params));
+	printd("bits   = %u\n",
+		snd_pcm_format_physical_width(params_format(params)));
+	printd("format = %d\n", params_format(params));
+
+	gpiod_set_value(reset, false);
+
+	switch (params_rate(params)) {
+	case 48000:
+		gpiod_set_value(osr0, true);
+		gpiod_set_value(osr1, false);
+		gpiod_set_value(osr2, false);
+		break;
+	case 96000:
+		gpiod_set_value(osr0, true);
+		gpiod_set_value(osr1, false);
+		gpiod_set_value(osr2, true);
+		break;
+	case 192000:
+		gpiod_set_value(osr0, true);
+		gpiod_set_value(osr1, true);
+		gpiod_set_value(osr2, true);
+		break;
+	default:
+		printe("Unsupported rate %u!\n", params_rate(params));
+		return -EINVAL;
+	}
+
+	gpiod_set_value(reset, true);
+
+	return 0;
+}
+
+static unsigned int rates[3] = {
+	48000, 96000, 192000
+};
+
+static struct snd_pcm_hw_constraint_list constraints_rates = {
+	.count = ARRAY_SIZE(rates),
+	.list = rates,
+	.mask = 0,
+};
+
+static int pisnd_startup(struct snd_pcm_substream *substream)
+{
+	int err = snd_pcm_hw_constraint_list(
+		substream->runtime,
+		0,
+		SNDRV_PCM_HW_PARAM_RATE,
+		&constraints_rates
+		);
+
+	if (err < 0)
+		return err;
+
+	err = snd_pcm_hw_constraint_single(
+		substream->runtime,
+		SNDRV_PCM_HW_PARAM_CHANNELS,
+		2
+		);
+
+	if (err < 0)
+		return err;
+
+	err = snd_pcm_hw_constraint_mask64(
+		substream->runtime,
+		SNDRV_PCM_HW_PARAM_FORMAT,
+		SNDRV_PCM_FMTBIT_S16_LE |
+		SNDRV_PCM_FMTBIT_S24_LE |
+		SNDRV_PCM_FMTBIT_S32_LE
+		);
+
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static struct snd_soc_ops pisnd_ops = {
+	.startup = pisnd_startup,
+	.hw_params = pisnd_hw_params,
+};
+
+static struct snd_soc_dai_link pisnd_dai[] = {
+	{
+		.name           = "pisound",
+		.stream_name    = "pisound",
+		.cpu_dai_name   = "bcm2708-i2s.0",
+		.codec_dai_name = "snd-soc-dummy-dai",
+		.platform_name  = "bcm2708-i2s.0",
+		.codec_name     = "snd-soc-dummy",
+		.dai_fmt        =
+			SND_SOC_DAIFMT_I2S |
+			SND_SOC_DAIFMT_NB_NF |
+			SND_SOC_DAIFMT_CBM_CFM,
+		.ops            = &pisnd_ops,
+	},
+};
+
+static int pisnd_card_probe(struct snd_soc_card *card)
+{
+	int err = pisnd_midi_init(card->snd_card);
+
+	if (err < 0) {
+		printe("pisnd_midi_init failed: %d\n", err);
+		return err;
+	}
+
+	err = pisnd_ctl_init(card->snd_card);
+	if (err < 0) {
+		printe("pisnd_ctl_init failed: %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static int pisnd_card_remove(struct snd_soc_card *card)
+{
+	pisnd_ctl_uninit();
+	pisnd_midi_uninit();
+	return 0;
+}
+
+static struct snd_soc_card pisnd_card = {
+	.name         = "pisound",
+	.owner        = THIS_MODULE,
+	.dai_link     = pisnd_dai,
+	.num_links    = ARRAY_SIZE(pisnd_dai),
+	.probe        = pisnd_card_probe,
+	.remove       = pisnd_card_remove,
+};
+
+static int pisnd_init_gpio(struct device *dev)
+{
+	osr0 = gpiod_get_index(dev, "osr", 0, GPIOD_ASIS);
+	osr1 = gpiod_get_index(dev, "osr", 1, GPIOD_ASIS);
+	osr2 = gpiod_get_index(dev, "osr", 2, GPIOD_ASIS);
+
+	reset = gpiod_get_index(dev, "reset", 0, GPIOD_ASIS);
+
+	button = gpiod_get_index(dev, "button", 0, GPIOD_ASIS);
+
+	gpiod_direction_output(osr0,  1);
+	gpiod_direction_output(osr1,  1);
+	gpiod_direction_output(osr2,  1);
+	gpiod_direction_output(reset, 1);
+
+	gpiod_set_value(reset, false);
+	gpiod_set_value(osr0,   true);
+	gpiod_set_value(osr1,  false);
+	gpiod_set_value(osr2,  false);
+	gpiod_set_value(reset,  true);
+
+	gpiod_export(button, false);
+
+	return 0;
+}
+
+static int pisnd_uninit_gpio(void)
+{
+	int i;
+
+	struct gpio_desc **gpios[] = {
+		&osr0, &osr1, &osr2, &reset, &button,
+	};
+
+	gpiod_unexport(button);
+
+	for (i = 0; i < ARRAY_SIZE(gpios); ++i) {
+		if (*gpios[i] == NULL) {
+			printd("weird, GPIO[%d] is NULL already\n", i);
+			continue;
+		}
+
+		gpiod_put(*gpios[i]);
+		*gpios[i] = NULL;
+	}
+
+	return 0;
+}
+
+static struct kobject *pisnd_kobj;
+
+static ssize_t pisnd_serial_show(
+	struct kobject *kobj,
+	struct kobj_attribute *attr,
+	char *buf
+	)
+{
+	return sprintf(buf, "%s\n", pisnd_spi_get_serial());
+}
+
+static ssize_t pisnd_id_show(
+	struct kobject *kobj,
+	struct kobj_attribute *attr,
+	char *buf
+	)
+{
+	return sprintf(buf, "%s\n", pisnd_spi_get_id());
+}
+
+static ssize_t pisnd_version_show(
+	struct kobject *kobj,
+	struct kobj_attribute *attr,
+	char *buf
+	)
+{
+	return sprintf(buf, "%s\n", pisnd_spi_get_version());
+}
+
+static ssize_t pisnd_led_store(
+	struct kobject *kobj,
+	struct kobj_attribute *attr,
+	const char *buf,
+	size_t length
+	)
+{
+	uint32_t timeout;
+	int err;
+
+	err = kstrtou32(buf, 10, &timeout);
+
+	if (err == 0 && timeout <= 255)
+		pisnd_spi_flash_leds(timeout);
+
+	return length;
+}
+
+static struct kobj_attribute pisnd_serial_attribute =
+	__ATTR(serial, 0444, pisnd_serial_show, NULL);
+static struct kobj_attribute pisnd_id_attribute =
+	__ATTR(id, 0444, pisnd_id_show, NULL);
+static struct kobj_attribute pisnd_version_attribute =
+	__ATTR(version, 0444, pisnd_version_show, NULL);
+static struct kobj_attribute pisnd_led_attribute =
+	__ATTR(led, 0644, NULL, pisnd_led_store);
+
+static struct attribute *attrs[] = {
+	&pisnd_serial_attribute.attr,
+	&pisnd_id_attribute.attr,
+	&pisnd_version_attribute.attr,
+	&pisnd_led_attribute.attr,
+	NULL
+};
+
+static struct attribute_group attr_group = { .attrs = attrs };
+
+static int pisnd_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+	int i;
+
+	ret = pisnd_spi_init(&pdev->dev);
+	if (ret < 0) {
+		printe("pisnd_spi_init failed: %d\n", ret);
+		return ret;
+	}
+
+	printi("Detected Pisound card:\n");
+	printi("\tSerial:  %s\n", pisnd_spi_get_serial());
+	printi("\tVersion: %s\n", pisnd_spi_get_version());
+	printi("\tId:      %s\n", pisnd_spi_get_id());
+
+	pisnd_kobj = kobject_create_and_add("pisound", kernel_kobj);
+	if (!pisnd_kobj) {
+		pisnd_spi_uninit();
+		return -ENOMEM;
+	}
+
+	ret = sysfs_create_group(pisnd_kobj, &attr_group);
+	if (ret < 0) {
+		pisnd_spi_uninit();
+		kobject_put(pisnd_kobj);
+		return -ENOMEM;
+	}
+
+	pisnd_init_gpio(&pdev->dev);
+	pisnd_card.dev = &pdev->dev;
+
+	if (pdev->dev.of_node) {
+		struct device_node *i2s_node;
+
+		i2s_node = of_parse_phandle(
+			pdev->dev.of_node,
+			"i2s-controller",
+			0
+			);
+
+		for (i = 0; i < pisnd_card.num_links; ++i) {
+			struct snd_soc_dai_link *dai = &pisnd_dai[i];
+
+			if (i2s_node) {
+				dai->cpu_dai_name = NULL;
+				dai->cpu_of_node = i2s_node;
+				dai->platform_name = NULL;
+				dai->platform_of_node = i2s_node;
+				dai->stream_name = pisnd_spi_get_serial();
+			}
+		}
+	}
+
+	ret = snd_soc_register_card(&pisnd_card);
+
+	if (ret < 0) {
+		if (ret != -EPROBE_DEFER)
+			printe("snd_soc_register_card() failed: %d\n", ret);
+		pisnd_uninit_gpio();
+		kobject_put(pisnd_kobj);
+		pisnd_spi_uninit();
+	}
+
+	return ret;
+}
+
+static int pisnd_remove(struct platform_device *pdev)
+{
+	printi("Unloading.\n");
+
+	if (pisnd_kobj) {
+		kobject_put(pisnd_kobj);
+		pisnd_kobj = NULL;
+	}
+
+	pisnd_spi_uninit();
+
+	/* Turn off */
+	gpiod_set_value(reset, false);
+	pisnd_uninit_gpio();
+
+	return snd_soc_unregister_card(&pisnd_card);
+}
+
+MODULE_DEVICE_TABLE(of, pisound_of_match);
+
+static struct platform_driver pisnd_driver = {
+	.driver = {
+		.name           = "snd-rpi-pisound",
+		.owner          = THIS_MODULE,
+		.of_match_table = pisound_of_match,
+	},
+	.probe              = pisnd_probe,
+	.remove             = pisnd_remove,
+};
+
+module_platform_driver(pisnd_driver);
+
+MODULE_AUTHOR("Giedrius Trainavicius <giedrius@blokas.io>");
+MODULE_DESCRIPTION("ASoC Driver for Pisound, https://blokas.io/pisound");
+MODULE_LICENSE("GPL v2");