openwrt/target/linux/bcm27xx/patches-6.6/950-1404-Adding-Pimidi-kernel-module.patch

From 8a6f640708627ac8ebf79f88793038933f169198 Mon Sep 17 00:00:00 2001
From: Giedrius <giedrius@blokas.io>
Date: Thu, 21 Nov 2024 08:04:02 +0000
Subject: [PATCH] Adding Pimidi kernel module.
MIME-Version: 1.0
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Signed-off-by: Giedrius Trainavičius <giedrius@blokas.io>
---
 sound/drivers/Kconfig  |   10 +
 sound/drivers/Makefile |    2 +
 sound/drivers/pimidi.c | 1113 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1125 insertions(+)
 create mode 100644 sound/drivers/pimidi.c

--- a/sound/drivers/Kconfig
+++ b/sound/drivers/Kconfig
@@ -263,4 +263,14 @@ config SND_AC97_POWER_SAVE_DEFAULT
 
 	  See SND_AC97_POWER_SAVE for more details.
 
+config SND_PIMIDI
+	tristate "Pimidi driver"
+	depends on SND_SEQUENCER && CRC8
+	select SND_RAWMIDI
+	help
+	  Say Y here to include support for Blokas Pimidi.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called snd-pimidi.
+
 endif	# SND_DRIVERS
--- a/sound/drivers/Makefile
+++ b/sound/drivers/Makefile
@@ -9,6 +9,7 @@ snd-aloop-objs := aloop.o
 snd-mtpav-objs := mtpav.o
 snd-mts64-objs := mts64.o
 snd-pcmtest-objs := pcmtest.o
+snd-pimidi-objs := pimidi.o
 snd-portman2x4-objs := portman2x4.o
 snd-serial-u16550-objs := serial-u16550.o
 snd-serial-generic-objs := serial-generic.o
@@ -23,6 +24,7 @@ obj-$(CONFIG_SND_SERIAL_U16550) += snd-s
 obj-$(CONFIG_SND_SERIAL_GENERIC) += snd-serial-generic.o
 obj-$(CONFIG_SND_MTPAV) += snd-mtpav.o
 obj-$(CONFIG_SND_MTS64) += snd-mts64.o
+obj-$(CONFIG_SND_PIMIDI) += snd-pimidi.o
 obj-$(CONFIG_SND_PORTMAN2X4) += snd-portman2x4.o
 
 obj-$(CONFIG_SND) += opl3/ opl4/ mpu401/ vx/ pcsp/
--- /dev/null
+++ b/sound/drivers/pimidi.c
@@ -0,0 +1,1113 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Pimidi Linux kernel module.
+ * Copyright (C) 2017-2024  Vilniaus Blokas UAB, https://blokas.io/
+ *
+ * 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.
+ */
+
+#include <linux/completion.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/irq.h>
+#include <linux/irqdesc.h>
+#include <linux/bitops.h>
+#include <linux/of_irq.h>
+#include <linux/kfifo.h>
+#include <linux/list.h>
+#include <linux/workqueue.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/mutex.h>
+#include <linux/refcount.h>
+#include <linux/crc8.h>
+#include <linux/delay.h>
+
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/rawmidi.h>
+#include <sound/asequencer.h>
+#include <sound/info.h>
+
+#define PIMIDI_LOG_IMPL(instance, log_func, msg, ...) log_func("pimidi(%s)[%c]: " msg "\n", \
+	__func__, (instance) ? (instance)->d + '0' : 'G', ## __VA_ARGS__)
+
+#ifdef PIMIDI_DEBUG
+#	define printd(instance, ...) PIMIDI_LOG_IMPL(instance, pr_alert, __VA_ARGS__)
+#	define printd_rl(instance, ...) PIMIDI_LOG_IMPL(instance, pr_alert_ratelimited, __VA_ARGS__)
+#	define printd_g(...) printd((struct pimidi_instance *)NULL, __VA_ARGS__)
+#else
+#	define printd(instance, ...) do {} while (0)
+#	define printd_rl(instance, ...) do {} while (0)
+#	define printd_g(...) do {} while (0)
+#endif
+
+#define printe(instance, ...) PIMIDI_LOG_IMPL(instance, pr_err, __VA_ARGS__)
+#define printe_rl(instance, ...) PIMIDI_LOG_IMPL(instance, pr_err_ratelimited, __VA_ARGS__)
+#define printi(instance, ...) PIMIDI_LOG_IMPL(instance, pr_info, __VA_ARGS__)
+#define printw(instance, ...) PIMIDI_LOG_IMPL(instance, pr_warn, __VA_ARGS__)
+#define printw_rl(instance, ...) PIMIDI_LOG_IMPL(instance, pr_warn_ratelimited, __VA_ARGS__)
+
+#define printe_g(...) printe((struct pimidi_instance *)NULL, __VA_ARGS__)
+#define printi_g(...) printi((struct pimidi_instance *)NULL, __VA_ARGS__)
+
+DECLARE_CRC8_TABLE(pimidi_crc8_table);
+enum { PIMIDI_CRC8_POLYNOMIAL = 0x83 };
+enum { PIMIDI_MAX_DEVICES = 4 };
+enum { PIMIDI_MAX_PACKET_SIZE = 17 };
+enum { PIMIDI_PORTS = 2 };
+
+struct pimidi_shared {
+	// lock protects the shared reset_gpio and devices list.
+	struct mutex            lock;
+	struct gpio_desc        *reset_gpio;
+	struct workqueue_struct *work_queue;
+	struct list_head        devices;
+};
+
+static struct pimidi_shared pimidi_global = {
+	.devices = LIST_HEAD_INIT(pimidi_global.devices),
+};
+
+struct pimidi_version_t {
+	u8 hwrev;
+	u8 major;
+	u8 minor;
+	u8 build;
+};
+
+enum { PIMIDI_IN_FIFO_SIZE = 4096 };
+
+struct pimidi_midi_port {
+	// in_lock protects the input substream.
+	struct mutex                      in_lock;
+	// out_lock protects the output substream.
+	struct mutex                      out_lock;
+	DECLARE_KFIFO(in_fifo, uint8_t, PIMIDI_IN_FIFO_SIZE);
+	unsigned int                      last_output_at;
+	unsigned int                      output_buffer_used_in_millibytes;
+	struct work_struct                in_handler;
+	struct delayed_work               out_handler;
+	unsigned long                     enabled_streams;
+	unsigned int                      tx_cnt;
+	unsigned int                      rx_cnt;
+};
+
+struct pimidi_instance {
+	struct list_head                  list;
+	struct i2c_client                 *i2c_client;
+	struct pimidi_version_t           version;
+	char                              serial[11];
+	char                              d;
+	struct gpio_desc                  *data_ready_gpio;
+
+	struct work_struct                drdy_handler;
+
+	// comm_lock serializes I2C communication.
+	struct mutex                      comm_lock;
+	char                              *rx_buf;
+	size_t                            rx_len;
+	int                               rx_status;
+	struct completion                 *rx_completion;
+
+	struct snd_rawmidi                *rawmidi;
+	struct pimidi_midi_port           midi_port[PIMIDI_PORTS];
+	bool                              stopping;
+};
+
+static struct snd_rawmidi_substream *pimidi_find_substream(struct snd_rawmidi *rawmidi,
+							   int stream,
+							   int number
+	)
+{
+	struct snd_rawmidi_substream *substream;
+
+	list_for_each_entry(substream, &rawmidi->streams[stream].substreams, list) {
+		if (substream->number == number)
+			return substream;
+	}
+	return NULL;
+}
+
+static void pimidi_midi_in_handler(struct pimidi_instance *instance, int port)
+{
+	int i, n, err;
+
+	printd(instance, "(%d)", port);
+
+	struct pimidi_midi_port *midi_port = &instance->midi_port[port];
+
+	if (!test_bit(SNDRV_RAWMIDI_STREAM_INPUT, &midi_port->enabled_streams)) {
+		printd(instance, "Input not enabled for %d", port);
+		return;
+	}
+
+	u8 data[512];
+
+	n = kfifo_out_peek(&midi_port->in_fifo, data, sizeof(data));
+	printd(instance, "Peeked %d MIDI bytes", n);
+
+	mutex_lock(&midi_port->in_lock);
+	struct snd_rawmidi_substream *substream =
+		pimidi_find_substream(instance->rawmidi,
+				      SNDRV_RAWMIDI_STREAM_INPUT,
+				      port);
+
+	err = snd_rawmidi_receive(substream, data, n);
+	if (err > 0)
+		midi_port->rx_cnt += err;
+	mutex_unlock(&midi_port->in_lock);
+
+	for (i = 0; i < err; ++i)
+		kfifo_skip(&midi_port->in_fifo);
+
+	if (n != err)
+		printw_rl(instance,
+			  "Not all MIDI data consumed for port %d: %d / %d", port, err, n);
+
+	if (!kfifo_is_empty(&midi_port->in_fifo) && !instance->stopping)
+		queue_work(pimidi_global.work_queue, &midi_port->in_handler);
+
+	printd(instance, "Done");
+}
+
+static void pimidi_midi_in_handler_0(struct work_struct *work)
+{
+	pimidi_midi_in_handler(container_of(work, struct pimidi_instance, midi_port[0].in_handler),
+			       0);
+}
+
+static void pimidi_midi_in_handler_1(struct work_struct *work)
+{
+	pimidi_midi_in_handler(container_of(work, struct pimidi_instance, midi_port[1].in_handler),
+			       1);
+}
+
+static void pimidi_midi_out_handler(struct pimidi_instance *instance, int port)
+{
+	printd(instance, "(%d)", port);
+	if (!test_bit(SNDRV_RAWMIDI_STREAM_OUTPUT, &instance->midi_port[port].enabled_streams)) {
+		printd(instance, "Output not enabled for %d", port);
+		return;
+	}
+
+	struct pimidi_midi_port *midi_port = &instance->midi_port[port];
+
+	struct snd_rawmidi_substream *substream =
+		pimidi_find_substream(instance->rawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, port);
+
+	mutex_lock(&midi_port->out_lock);
+
+	enum { MIDI_MILLI_BYTES_PER_JIFFY = 3125000 / HZ };
+	enum { MIDI_MAX_OUTPUT_BUFFER_SIZE_IN_MILLIBYTES =
+		(512 - PIMIDI_MAX_PACKET_SIZE - 1) * 1000 };
+
+	unsigned int now = jiffies;
+	unsigned int millibytes_became_available =
+		(MIDI_MILLI_BYTES_PER_JIFFY) * (now - midi_port->last_output_at);
+
+	midi_port->output_buffer_used_in_millibytes =
+		midi_port->output_buffer_used_in_millibytes <=
+		millibytes_became_available ? 0 : midi_port->output_buffer_used_in_millibytes -
+		millibytes_became_available;
+
+	unsigned int output_buffer_available =
+		(MIDI_MAX_OUTPUT_BUFFER_SIZE_IN_MILLIBYTES
+		- midi_port->output_buffer_used_in_millibytes)
+		/ 1000;
+
+	u8 buffer[PIMIDI_MAX_PACKET_SIZE];
+	int n, batch, err;
+
+	for (batch = 0; batch < 3; ++batch) {
+		if (output_buffer_available == 0)
+			printd(instance, "Buffer full");
+
+		printd(instance, "Buffer available: %u (%u +%u, %u -> %u, dt %u) (%u) @ %u",
+		       output_buffer_available, midi_port->output_buffer_used_in_millibytes,
+		       millibytes_became_available, midi_port->last_output_at, now,
+		       now - midi_port->last_output_at, midi_port->tx_cnt, HZ);
+		midi_port->last_output_at = now;
+
+		n = output_buffer_available
+			? snd_rawmidi_transmit_peek(substream, buffer + 1,
+						    min(output_buffer_available,
+							sizeof(buffer) - 2))
+			: 0;
+		if (n > 0) {
+			printd(instance, "Peeked: %d", n);
+			snd_rawmidi_transmit_ack(substream, n);
+
+			buffer[0] = (port << 4) | n;
+			buffer[n + 1] = ~crc8(pimidi_crc8_table, buffer, n + 1, CRC8_INIT_VALUE);
+
+#ifdef PIMIDI_DEBUG
+			pr_debug("%s[%d]: Sending %d bytes:", __func__, instance->d, n + 2);
+			int i;
+
+			for (i = 0; i < n + 2; ++i)
+				pr_cont(" %02x", buffer[i]);
+
+			pr_cont("\n");
+#endif
+			mutex_lock(&instance->comm_lock);
+			err = i2c_master_send(instance->i2c_client, buffer, n + 2);
+			mutex_unlock(&instance->comm_lock);
+
+			if (err < 0) {
+				printe(instance,
+				       "Error occurred when sending MIDI data over I2C! (%d)",
+				       err);
+				goto cleanup;
+			}
+
+			midi_port->tx_cnt += n;
+			midi_port->output_buffer_used_in_millibytes += n * 1000;
+			output_buffer_available -= n;
+		} else if (n < 0) {
+			err = n;
+			printe(instance, "snd_rawmidi_transmit_peek returned error %d!", err);
+			goto cleanup;
+		} else {
+			break;
+		}
+	}
+
+	printd(instance, "Checking if empty %p", substream);
+	if (!snd_rawmidi_transmit_empty(substream) && !instance->stopping) {
+		unsigned int delay = 1;
+
+		if (output_buffer_available == 0)
+			delay = 125000 / MIDI_MILLI_BYTES_PER_JIFFY;
+		printd(instance, "Queue more work after %u jiffies", delay);
+		mod_delayed_work(pimidi_global.work_queue, &midi_port->out_handler, delay);
+	}
+
+cleanup:
+	mutex_unlock(&midi_port->out_lock);
+	printd(instance, "Done");
+}
+
+static void pimidi_midi_out_handler_0(struct work_struct *work)
+{
+	pimidi_midi_out_handler(container_of(work, struct pimidi_instance,
+					     midi_port[0].out_handler.work), 0);
+}
+
+static void pimidi_midi_out_handler_1(struct work_struct *work)
+{
+	pimidi_midi_out_handler(container_of(work, struct pimidi_instance,
+					     midi_port[1].out_handler.work), 1);
+}
+
+static void pimidi_midi_output_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+	struct pimidi_instance *instance = substream->rmidi->private_data;
+
+	printd(instance, "(%d, %d, %d)", substream->stream, substream->number, up);
+
+	if (up == 0) {
+		clear_bit(substream->stream,
+			  &instance->midi_port[substream->number].enabled_streams);
+	} else {
+		set_bit(substream->stream,
+			&instance->midi_port[substream->number].enabled_streams);
+		if (!delayed_work_pending(&instance->midi_port[substream->number].out_handler)) {
+			printd(instance, "Queueing work");
+			queue_delayed_work(pimidi_global.work_queue,
+					   &instance->midi_port[substream->number].out_handler, 0);
+		}
+	}
+}
+
+static void pimidi_midi_output_drain(struct snd_rawmidi_substream *substream)
+{
+	struct pimidi_instance *instance = substream->rmidi->private_data;
+
+	printd(instance, "(%d, %d)", substream->stream, substream->number);
+
+	printd(instance, "Begin draining!");
+
+	queue_delayed_work(pimidi_global.work_queue,
+			   &instance->midi_port[substream->number].out_handler, 0);
+
+	unsigned long deadline = jiffies + 5 * HZ;
+
+	do {
+		printd(instance, "Before flush");
+		while (delayed_work_pending(&instance->midi_port[substream->number].out_handler))
+			flush_delayed_work(&instance->midi_port[substream->number].out_handler);
+		printd(instance, "Flushed");
+	} while (!snd_rawmidi_transmit_empty(substream) && time_before(jiffies, deadline));
+
+	printd(instance, "Done!");
+}
+
+static int pimidi_midi_output_close(struct snd_rawmidi_substream *substream)
+{
+	struct pimidi_instance *instance = substream->rmidi->private_data;
+	struct pimidi_midi_port *midi_port = &instance->midi_port[substream->number];
+
+	mutex_lock(&midi_port->out_lock);
+	clear_bit(substream->stream, &midi_port->enabled_streams);
+	mutex_unlock(&midi_port->out_lock);
+	return 0;
+}
+
+static int pimidi_midi_input_close(struct snd_rawmidi_substream *substream)
+{
+	struct pimidi_instance *instance = substream->rmidi->private_data;
+	struct pimidi_midi_port *midi_port = &instance->midi_port[substream->number];
+
+	mutex_lock(&midi_port->in_lock);
+	clear_bit(substream->stream, &midi_port->enabled_streams);
+	mutex_unlock(&midi_port->in_lock);
+	return 0;
+}
+
+static void pimidi_midi_input_trigger(struct snd_rawmidi_substream *substream, int up)
+{
+	struct pimidi_instance *instance = substream->rmidi->private_data;
+
+	printd(instance, "(%d, %d, %d)", substream->stream, substream->number, up);
+
+	if (up == 0) {
+		clear_bit(substream->stream,
+			  &instance->midi_port[substream->number].enabled_streams);
+		cancel_work_sync(&instance->midi_port[substream->number].in_handler);
+	} else {
+		set_bit(substream->stream,
+			&instance->midi_port[substream->number].enabled_streams);
+		if (!instance->stopping)
+			queue_work(pimidi_global.work_queue,
+				   &instance->midi_port[substream->number].in_handler);
+	}
+}
+
+static void pimidi_get_port_info(struct snd_rawmidi *rmidi, int number,
+				 struct snd_seq_port_info *seq_port_info)
+{
+	printd_g("%p, %d, %p", rmidi, number, seq_port_info);
+	seq_port_info->type =
+		SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC |
+		SNDRV_SEQ_PORT_TYPE_HARDWARE |
+		SNDRV_SEQ_PORT_TYPE_PORT;
+	strscpy(seq_port_info->name, number == 0 ? "a" : "b",
+		sizeof(seq_port_info->name));
+	seq_port_info->midi_voices = 0;
+}
+
+static const struct snd_rawmidi_global_ops pimidi_midi_ops = {
+	.get_port_info = pimidi_get_port_info,
+};
+
+static int pimidi_midi_open(struct snd_rawmidi_substream *substream)
+{
+	printd_g("(%p) stream=%d number=%d", substream, substream->stream, substream->number);
+	return 0;
+}
+
+static const struct snd_rawmidi_ops pimidi_midi_output_ops = {
+	.open = pimidi_midi_open,
+	.close = pimidi_midi_output_close,
+	.trigger = pimidi_midi_output_trigger,
+	.drain = pimidi_midi_output_drain,
+};
+
+static const struct snd_rawmidi_ops pimidi_midi_input_ops = {
+	.open = pimidi_midi_open,
+	.close = pimidi_midi_input_close,
+	.trigger = pimidi_midi_input_trigger,
+};
+
+static int pimidi_register(struct pimidi_instance *instance)
+{
+	int err = 0;
+
+	mutex_lock(&pimidi_global.lock);
+	printd(instance, "Registering...");
+	if (!pimidi_global.reset_gpio) {
+		printd_g("Getting reset pin.");
+		pimidi_global.reset_gpio = gpiod_get(&instance->i2c_client->dev, "reset",
+						     GPIOD_OUT_LOW);
+		if (IS_ERR(pimidi_global.reset_gpio)) {
+			err = PTR_ERR(pimidi_global.reset_gpio);
+			printe_g("gpiod_get failed: %d", err);
+			pimidi_global.reset_gpio = NULL;
+			mutex_unlock(&pimidi_global.lock);
+			return err;
+		}
+	}
+	list_add_tail(&instance->list, &pimidi_global.devices);
+	mutex_unlock(&pimidi_global.lock);
+	return err;
+}
+
+static void pimidi_unregister(struct pimidi_instance *instance)
+{
+	mutex_lock(&pimidi_global.lock);
+	printd(instance, "Unregistering...");
+	list_del(&instance->list);
+	if (list_empty(&pimidi_global.devices)) {
+		printd_g("Releasing reset pin");
+		gpiod_put(pimidi_global.reset_gpio);
+		pimidi_global.reset_gpio = NULL;
+	}
+	mutex_unlock(&pimidi_global.lock);
+}
+
+static void pimidi_perform_reset(void)
+{
+	mutex_lock(&pimidi_global.lock);
+
+	printd_g("Performing reset.");
+
+	struct list_head *p;
+
+	list_for_each(p, &pimidi_global.devices) {
+		struct pimidi_instance *instance = list_entry(p, struct pimidi_instance, list);
+
+		printd(instance, "Pausing...");
+		instance->stopping = true;
+		disable_irq(instance->i2c_client->irq);
+		cancel_work(&instance->drdy_handler);
+
+		int i;
+
+		for (i = 0; i < PIMIDI_PORTS; ++i) {
+			cancel_work(&instance->midi_port[i].in_handler);
+			cancel_delayed_work(&instance->midi_port[i].out_handler);
+		}
+
+		drain_workqueue(pimidi_global.work_queue);
+	}
+
+	printd_g("Reset = low");
+	gpiod_set_value(pimidi_global.reset_gpio, 1);
+
+	list_for_each(p, &pimidi_global.devices) {
+		struct pimidi_instance *instance = list_entry(p, struct pimidi_instance, list);
+
+		if (gpiod_is_active_low(instance->data_ready_gpio))
+			gpiod_toggle_active_low(instance->data_ready_gpio);
+		gpiod_direction_output(instance->data_ready_gpio, 1);
+		printd(instance, "DRDY high");
+	}
+
+	usleep_range(1000, 5000);
+	printd_g("Reset = high");
+	gpiod_set_value(pimidi_global.reset_gpio, 0);
+	msleep(30);
+
+	int i;
+
+	for (i = 0; i < PIMIDI_MAX_DEVICES; ++i) {
+		usleep_range(1000, 3000);
+		list_for_each(p, &pimidi_global.devices) {
+			struct pimidi_instance *instance = list_entry(p, struct pimidi_instance,
+								      list);
+
+			if (instance->d < i)
+				continue;
+			printd(instance, "DRDY -> %d", !gpiod_get_value(instance->data_ready_gpio));
+			gpiod_set_value(instance->data_ready_gpio,
+					!gpiod_get_value(instance->data_ready_gpio));
+		}
+	}
+	usleep_range(16000, 20000);
+
+	list_for_each(p, &pimidi_global.devices) {
+		struct pimidi_instance *instance = list_entry(p, struct pimidi_instance, list);
+
+		if (!gpiod_is_active_low(instance->data_ready_gpio))
+			gpiod_toggle_active_low(instance->data_ready_gpio);
+
+		printd(instance, "DRDY input");
+		gpiod_direction_input(instance->data_ready_gpio);
+
+		printd(instance, "Resume...");
+		instance->stopping = false;
+		enable_irq(instance->i2c_client->irq);
+	}
+
+	printd_g("Reset done.");
+	usleep_range(16000, 20000);
+
+	mutex_unlock(&pimidi_global.lock);
+}
+
+static int pimidi_read_version(struct pimidi_version_t *version, struct pimidi_instance *instance)
+{
+	memset(version, 0, sizeof(*version));
+
+	const char cmd[4] = { 0xb2, 0x01, 0x01, 0x95 };
+
+	char result[9];
+
+	memset(result, 0, sizeof(result));
+
+	DECLARE_COMPLETION_ONSTACK(done);
+
+	mutex_lock(&instance->comm_lock);
+	int err = i2c_master_send(instance->i2c_client, cmd, sizeof(cmd));
+
+	if (err < 0) {
+		mutex_unlock(&instance->comm_lock);
+		return err;
+	}
+	instance->rx_buf = result;
+	instance->rx_len = sizeof(result);
+	instance->rx_completion = &done;
+	mutex_unlock(&instance->comm_lock);
+
+	printd(instance, "Waiting for drdy");
+	wait_for_completion_io_timeout(&done, msecs_to_jiffies(1000u));
+	printd(instance, "Done waiting");
+
+	if (!completion_done(&done)) {
+		mutex_lock(&instance->comm_lock);
+		instance->rx_buf = NULL;
+		instance->rx_len = 0;
+		instance->rx_status = -ETIMEDOUT;
+		instance->rx_completion = NULL;
+		mutex_unlock(&instance->comm_lock);
+		return -ETIMEDOUT;
+	}
+
+	if (CRC8_GOOD_VALUE(pimidi_crc8_table) != crc8(pimidi_crc8_table, result, sizeof(result),
+						       CRC8_INIT_VALUE))
+		return -EIO;
+
+	const char expected[4] = { 0xb7, 0x81, 0x01, 0x00 };
+
+	if (memcmp(result, expected, sizeof(expected)) != 0)
+		return -EPROTO;
+
+	u32 v = ntohl(*(uint32_t *)(result + 4));
+
+	version->hwrev = v >> 24;
+	version->major = (v & 0x00ff0000) >> 16;
+	version->minor = (v & 0x0000ff00) >> 8;
+	version->build = v & 0x000000ff;
+
+	return 0;
+}
+
+static int pimidi_read_serial(char serial[11], struct pimidi_instance *instance)
+{
+	memset(serial, 0, sizeof(char[11]));
+
+	const char cmd[4] = { 0xb2, 0x03, 0x04, 0x97 };
+
+	char result[PIMIDI_MAX_PACKET_SIZE];
+
+	memset(result, 0, sizeof(result));
+
+	DECLARE_COMPLETION_ONSTACK(done);
+
+	mutex_lock(&instance->comm_lock);
+	int err = i2c_master_send(instance->i2c_client, cmd, sizeof(cmd));
+
+	if (err < 0) {
+		mutex_unlock(&instance->comm_lock);
+		return err;
+	}
+	instance->rx_buf = result;
+	instance->rx_len = sizeof(result);
+	instance->rx_completion = &done;
+	mutex_unlock(&instance->comm_lock);
+
+	printd(instance, "Waiting for drdy");
+	wait_for_completion_io_timeout(&done, msecs_to_jiffies(1000u));
+	printd(instance, "Done waiting");
+
+	if (!completion_done(&done)) {
+		mutex_lock(&instance->comm_lock);
+		instance->rx_buf = NULL;
+		instance->rx_len = 0;
+		instance->rx_status = -ETIMEDOUT;
+		instance->rx_completion = NULL;
+		mutex_unlock(&instance->comm_lock);
+		printe(instance, "Timed out");
+		return -ETIMEDOUT;
+	}
+
+	if (CRC8_GOOD_VALUE(pimidi_crc8_table) != crc8(pimidi_crc8_table, result,
+						       (result[0] & 0x0f) + 2, CRC8_INIT_VALUE))
+		return -EIO;
+
+	const char expected[4] = { 0xbd, 0x83, 0x04, 0x0a };
+
+	if (memcmp(result, expected, sizeof(expected)) != 0) {
+		printe(instance, "Unexpected response: %02x %02x %02x %02x", result[0], result[1],
+		       result[2], result[3]);
+		return -EPROTO;
+	}
+
+	memcpy(serial, result + 4, 10);
+
+	if (strspn(serial, "\xff") == 10)
+		strscpy(serial, "(unset)", 8);
+
+	return 0;
+}
+
+static void pimidi_handle_midi_data(struct pimidi_instance *instance, int port, const uint8_t *data,
+				    unsigned int n)
+{
+	printd(instance, "Handling MIDI data for port %d (%u bytes)", port, n);
+	if (n == 0)
+		return;
+
+	struct pimidi_midi_port *midi_port = &instance->midi_port[port];
+
+	kfifo_in(&midi_port->in_fifo, data, n);
+
+	if (!instance->stopping)
+		queue_work(pimidi_global.work_queue, &midi_port->in_handler);
+
+	printd(instance, "Done");
+}
+
+static void pimidi_drdy_continue(struct pimidi_instance *instance)
+{
+	if (instance->stopping) {
+		printd(instance, "Refusing to queue work / enable IRQ due to stopping.");
+		return;
+	}
+
+	if (gpiod_get_value(instance->data_ready_gpio)) {
+		printd_rl(instance, "Queue work due to DRDY line still low");
+		queue_work(pimidi_global.work_queue, &instance->drdy_handler);
+	} else {
+		printd_rl(instance, "Enabling irq for more data");
+		enable_irq(gpiod_to_irq(instance->data_ready_gpio));
+	}
+}
+
+static void pimidi_drdy_handler(struct work_struct *work)
+{
+	struct pimidi_instance *instance = container_of(work, struct pimidi_instance, drdy_handler);
+
+	printd(instance, "(%p)", work);
+
+	mutex_lock(&instance->comm_lock);
+	if (!instance->rx_completion) {
+		u8 data[PIMIDI_MAX_PACKET_SIZE];
+		int n = i2c_master_recv(instance->i2c_client, data, 3);
+
+		if (n < 0) {
+			printe(instance, "Error reading from device: %d", n);
+			mutex_unlock(&instance->comm_lock);
+			pimidi_drdy_continue(instance);
+			return;
+		}
+
+		if (data[0] == 0xfe) {
+			printe_rl(instance, "Invalid packet 0x%02x 0x%02x 0x%02x", data[0], data[1],
+				  data[2]);
+			mutex_unlock(&instance->comm_lock);
+			pimidi_drdy_continue(instance);
+			return;
+		}
+
+		int len = (data[0] & 0x0f) + 2;
+
+		if (len > n) {
+			printd(instance, "Need %d more bytes", len - n);
+			int err = i2c_master_recv(instance->i2c_client, data + n, len - n);
+
+			if (err < 0) {
+				printe(instance, "Error reading remainder from device: %d", err);
+				mutex_unlock(&instance->comm_lock);
+				pimidi_drdy_continue(instance);
+				return;
+#ifdef PIMIDI_DEBUG
+			} else {
+				pr_debug("Recv_2:");
+				int i;
+
+				for (i = n; i < len; ++i)
+					pr_cont(" %02x", data[i]);
+				pr_cont("\n");
+#endif
+			}
+		}
+
+		if (CRC8_GOOD_VALUE(pimidi_crc8_table) == crc8(pimidi_crc8_table, data, len,
+							       CRC8_INIT_VALUE)) {
+			switch (data[0] & 0xf0) {
+			case 0x00:
+				pimidi_handle_midi_data(instance, 0, data + 1, len - 2);
+				break;
+			case 0x10:
+				pimidi_handle_midi_data(instance, 1, data + 1, len - 2);
+				break;
+			default:
+				printd(instance, "Unhandled command %02x", data[0]);
+				break;
+			}
+		} else {
+			printe(instance, "I2C rx corruption detected.");
+			pr_info("Packet [%d]:", len);
+			int i;
+
+			for (i = 0; i < len; ++i)
+				pr_cont(" %02x", data[i]);
+			pr_cont("\n");
+		}
+
+		mutex_unlock(&instance->comm_lock);
+	} else {
+		printd(instance, "Completing drdy");
+		instance->rx_status = i2c_master_recv(instance->i2c_client, instance->rx_buf, 3);
+		printd(instance, "Recv_1 %02x %02x %02x", instance->rx_buf[0], instance->rx_buf[1],
+		       instance->rx_buf[2]);
+		if (instance->rx_len > 3 && instance->rx_status == 3) {
+			instance->rx_status = i2c_master_recv(instance->i2c_client,
+							      instance->rx_buf + 3,
+							      instance->rx_len - 3);
+			if (instance->rx_status >= 0)
+				instance->rx_status += 3;
+#ifdef PIMIDI_DEBUG
+			pr_debug("Recv_2:");
+			int i;
+
+			for (i = 3; i < instance->rx_len; ++i)
+				pr_cont(" %02x", instance->rx_buf[i]);
+			pr_cont("\n");
+#endif
+		}
+		struct completion *done = instance->rx_completion;
+
+		instance->rx_buf = NULL;
+		instance->rx_len = 0;
+		instance->rx_completion = NULL;
+		complete_all(done);
+		mutex_unlock(&instance->comm_lock);
+	}
+
+	pimidi_drdy_continue(instance);
+}
+
+static irqreturn_t pimidi_drdy_interrupt_handler(int irq, void *dev_id)
+{
+	struct pimidi_instance *instance = (struct pimidi_instance *)dev_id;
+
+	if (instance->stopping) {
+		printd(instance, "DRDY interrupt, but stopping, ignoring...");
+		return IRQ_HANDLED;
+	}
+
+	printd(instance, "DRDY interrupt, masking");
+	disable_irq_nosync(irq);
+
+	printd(instance, "Queue work due to DRDY interrupt");
+	queue_work(pimidi_global.work_queue, &instance->drdy_handler);
+
+	return IRQ_HANDLED;
+}
+
+static void pimidi_proc_stat_show(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
+{
+	const unsigned int *d = entry->private_data;
+
+	snd_iprintf(buffer, "%u\n", *d);
+}
+
+static void pimidi_proc_serial_show(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
+{
+	struct pimidi_instance *instance = entry->private_data;
+
+	snd_iprintf(buffer, "%s\n", instance->serial);
+}
+
+static void pimidi_proc_version_show(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
+{
+	struct pimidi_instance *instance = entry->private_data;
+
+	snd_iprintf(buffer, "%u.%u.%u\n", instance->version.major, instance->version.minor,
+		    instance->version.build);
+}
+
+static void pimidi_proc_hwrev_show(struct snd_info_entry *entry, struct snd_info_buffer *buffer)
+{
+	struct pimidi_instance *instance = entry->private_data;
+
+	snd_iprintf(buffer, "%u\n", instance->version.hwrev);
+}
+
+static int pimidi_i2c_probe(struct i2c_client *client)
+{
+	struct snd_card *card = NULL;
+	int err, d, i;
+
+	d = client->addr - 0x20;
+
+	if (d < 0 || d >= 8) {
+		printe_g("Unexpected device address: %d", client->addr);
+		err = -EINVAL;
+		goto finalize;
+	}
+
+	err = snd_card_new(&client->dev, SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1, THIS_MODULE,
+			   sizeof(struct pimidi_instance), &card);
+
+	if (err) {
+		printe_g("snd_card_new failed: %d", err);
+		return err;
+	}
+
+	struct pimidi_instance *instance = (struct pimidi_instance *)card->private_data;
+
+	instance->i2c_client = client;
+	instance->d = d;
+
+	struct snd_rawmidi *rawmidi;
+
+	err = snd_rawmidi_new(card, card->shortname, 0, 2, 2, &rawmidi);
+	if (err < 0) {
+		printe(instance, "snd_rawmidi_new failed: %d", err);
+		goto finalize;
+	}
+
+	instance->rawmidi = rawmidi;
+	strscpy(rawmidi->name, "pimidi", sizeof(rawmidi->name));
+
+	rawmidi->info_flags =
+		SNDRV_RAWMIDI_INFO_OUTPUT | SNDRV_RAWMIDI_INFO_INPUT | SNDRV_RAWMIDI_INFO_DUPLEX;
+	rawmidi->private_data = instance;
+	rawmidi->ops = &pimidi_midi_ops;
+
+	snd_rawmidi_set_ops(rawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &pimidi_midi_output_ops);
+	snd_rawmidi_set_ops(rawmidi, SNDRV_RAWMIDI_STREAM_INPUT, &pimidi_midi_input_ops);
+
+	instance->data_ready_gpio = devm_gpiod_get(&client->dev, "data-ready", GPIOD_OUT_HIGH);
+	if (IS_ERR(instance->data_ready_gpio)) {
+		err = PTR_ERR(instance->data_ready_gpio);
+		printe(instance, "devm_gpiod_get failed: %d", err);
+		goto finalize;
+	}
+
+	err = pimidi_register(instance);
+	if (err < 0) {
+		printe(instance, "pimidi_register failed: %d", err);
+		goto finalize;
+	}
+
+	pimidi_perform_reset();
+
+	INIT_WORK(&instance->drdy_handler, pimidi_drdy_handler);
+	mutex_init(&instance->comm_lock);
+
+	err = devm_request_irq(&client->dev, client->irq, pimidi_drdy_interrupt_handler,
+			       IRQF_SHARED | IRQF_TRIGGER_LOW, "data_ready_int", instance);
+
+	if (err != 0) {
+		printe(instance, "data_available IRQ request failed! %d", err);
+		goto finalize;
+	}
+
+	err = pimidi_read_version(&instance->version, instance);
+	if (err < 0) {
+		printe(instance, "pimidi_read_version failed: %d", err);
+		goto finalize;
+	}
+
+	err = pimidi_read_serial(instance->serial, instance);
+	if (err < 0) {
+		printe(instance, "pimidi_read_serial failed: %d", err);
+		goto finalize;
+	} else if (instance->serial[0] != 'P' || instance->serial[1] != 'M' ||
+		   strlen(instance->serial) != 10) {
+		printe(instance, "Unexpected serial number: %s", instance->serial);
+		err = -EIO;
+		goto finalize;
+	}
+
+	printi(instance, "pimidi%d hw:%d version %u.%u.%u-%u, serial %s",
+	       d,
+	       card->number,
+	       instance->version.major,
+	       instance->version.minor,
+	       instance->version.build,
+	       instance->version.hwrev,
+	       instance->serial
+	       );
+
+	strscpy(card->driver, "snd-pimidi", sizeof(card->driver));
+	snprintf(card->shortname, sizeof(card->shortname), "pimidi%d", d);
+	snprintf(card->longname, sizeof(card->longname), "pimidi%d %s", d, instance->serial);
+	snprintf(card->id, sizeof(card->id), "pimidi%d", d);
+
+	snprintf(pimidi_find_substream(rawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, 0)->name,
+		 10u, "pimidi%d-a", d);
+	snprintf(pimidi_find_substream(rawmidi, SNDRV_RAWMIDI_STREAM_INPUT,  0)->name,
+		 10u, "pimidi%d-a", d);
+	snprintf(pimidi_find_substream(rawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, 1)->name,
+		 10u, "pimidi%d-b", d);
+	snprintf(pimidi_find_substream(rawmidi, SNDRV_RAWMIDI_STREAM_INPUT,  1)->name,
+		 10u, "pimidi%d-b", d);
+
+	err = snd_card_ro_proc_new(card, "a-tx", &instance->midi_port[0].tx_cnt,
+				   pimidi_proc_stat_show);
+	err = snd_card_ro_proc_new(card, "a-rx", &instance->midi_port[0].rx_cnt,
+				   pimidi_proc_stat_show);
+	err = snd_card_ro_proc_new(card, "b-tx", &instance->midi_port[1].tx_cnt,
+				   pimidi_proc_stat_show);
+	err = snd_card_ro_proc_new(card, "b-rx", &instance->midi_port[1].rx_cnt,
+				   pimidi_proc_stat_show);
+	err = snd_card_ro_proc_new(card, "serial", instance, pimidi_proc_serial_show);
+	err = snd_card_ro_proc_new(card, "version", instance, pimidi_proc_version_show);
+	err = snd_card_ro_proc_new(card, "hwrev", instance, pimidi_proc_hwrev_show);
+	if (err < 0) {
+		printe(instance, "snd_card_ro_proc_new failed: %d", err);
+		goto finalize;
+	}
+
+	err = snd_card_register(card);
+	if (err < 0) {
+		printe(instance, "snd_card_register failed: %d", err);
+		goto finalize;
+	}
+
+finalize:
+	if (err) {
+		instance->stopping = true;
+		cancel_work_sync(&instance->drdy_handler);
+		mutex_destroy(&instance->comm_lock);
+		pimidi_unregister(instance);
+		snd_card_free(card);
+		return err;
+	}
+
+	for (i = 0; i < PIMIDI_PORTS; ++i) {
+		struct pimidi_midi_port *port = &instance->midi_port[i];
+
+		mutex_init(&port->in_lock);
+		mutex_init(&port->out_lock);
+		INIT_WORK(&port->in_handler,
+			  i == 0 ? pimidi_midi_in_handler_0 : pimidi_midi_in_handler_1);
+		INIT_DELAYED_WORK(&port->out_handler,
+				  i == 0 ? pimidi_midi_out_handler_0 : pimidi_midi_out_handler_1);
+		INIT_KFIFO(port->in_fifo);
+		port->last_output_at = jiffies;
+	}
+
+	i2c_set_clientdata(client, card);
+	return 0;
+}
+
+static void pimidi_i2c_remove(struct i2c_client *client)
+{
+	printd_g("(%p)", client);
+
+	int i;
+	struct snd_card *card = i2c_get_clientdata(client);
+
+	if (card) {
+		printi_g("Unloading hw:%d %s", card->number, card->longname);
+		struct pimidi_instance *instance = (struct pimidi_instance *)card->private_data;
+
+		instance->stopping = true;
+		i2c_set_clientdata(client, NULL);
+		devm_free_irq(&client->dev, client->irq, instance);
+		cancel_work_sync(&instance->drdy_handler);
+
+		for (i = 0; i < PIMIDI_PORTS; ++i) {
+			cancel_work_sync(&instance->midi_port[i].in_handler);
+			cancel_delayed_work_sync(&instance->midi_port[i].out_handler);
+			mutex_destroy(&instance->midi_port[i].out_lock);
+			mutex_destroy(&instance->midi_port[i].in_lock);
+			kfifo_free(&instance->midi_port[i].in_fifo);
+		}
+
+		mutex_destroy(&instance->comm_lock);
+		pimidi_unregister(instance);
+		snd_card_free(card);
+	}
+}
+
+static const struct i2c_device_id pimidi_i2c_ids[] = {
+	{ "pimidi", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, pimidi_i2c_ids);
+
+static const struct of_device_id pimidi_i2c_dt_ids[] = {
+	{ .compatible = "blokaslabs,pimidi", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, pimidi_i2c_dt_ids);
+
+static struct i2c_driver pimidi_i2c_driver = {
+	.driver = {
+		.name = "pimidi",
+		.owner = THIS_MODULE,
+		.of_match_table = of_match_ptr(pimidi_i2c_dt_ids),
+	},
+	.probe = pimidi_i2c_probe,
+	.remove = pimidi_i2c_remove,
+	.id_table = pimidi_i2c_ids,
+};
+
+int pimidi_module_init(void)
+{
+	int err = 0;
+
+	mutex_init(&pimidi_global.lock);
+
+	INIT_LIST_HEAD(&pimidi_global.devices);
+
+	pimidi_global.work_queue = create_singlethread_workqueue("pimidi");
+	if (!pimidi_global.work_queue) {
+		err = -ENOMEM;
+		goto cleanup;
+	}
+
+	err = i2c_add_driver(&pimidi_i2c_driver);
+	if (err < 0)
+		goto cleanup;
+
+	crc8_populate_msb(pimidi_crc8_table, PIMIDI_CRC8_POLYNOMIAL);
+
+	return 0;
+
+cleanup:
+	mutex_destroy(&pimidi_global.lock);
+	return err;
+}
+
+void pimidi_module_exit(void)
+{
+	i2c_del_driver(&pimidi_i2c_driver);
+	mutex_lock(&pimidi_global.lock);
+	if (pimidi_global.reset_gpio) {
+		gpiod_put(pimidi_global.reset_gpio);
+		pimidi_global.reset_gpio = NULL;
+	}
+	mutex_unlock(&pimidi_global.lock);
+
+	destroy_workqueue(pimidi_global.work_queue);
+	pimidi_global.work_queue = NULL;
+
+	mutex_destroy(&pimidi_global.lock);
+}
+
+module_init(pimidi_module_init);
+module_exit(pimidi_module_exit);
+
+MODULE_AUTHOR("Giedrius Trainavi\xc4\x8dius <giedrius@blokas.io>");
+MODULE_DESCRIPTION("MIDI driver for Blokas Pimidi, https://blokas.io/");
+MODULE_LICENSE("GPL");
+
+/* vim: set ts=8 sw=8 noexpandtab: */