ALSA: Add ALSA driver for Atmel Audio Bitstream DAC

This patch adds ALSA support for the Audio Bistream DAC found on Atmel
AVR32 devices. The ABDAC is an Atmel IP which might show up on AT91
devices in the future, hence making a generic driver which can be
utilized by AT91 arch if needed.

Datasheet describing the ABDAC peripheral is available in the AT32AP7000
datasheet, http://www.atmel.com/dyn/products/datasheets.asp?family_id=682

Tested on ATSTK1006 + ATSTK1000 with a class D amplifier stage.

Signed-off-by: Hans-Christian Egtvedt <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

include/sound/atmel-abdac.h

···
+/*
+ * Driver for the Atmel Audio Bitstream DAC (ABDAC)
+ *
+ * Copyright (C) 2009 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ */
+#ifndef __INCLUDE_SOUND_ATMEL_ABDAC_H
+#define __INCLUDE_SOUND_ATMEL_ABDAC_H
+
+#include <linux/dw_dmac.h>
+
+/**
+ * struct atmel_abdac_pdata - board specific ABDAC configuration
+ * @dws: DMA slave interface to use for sound playback.
+ */
+struct atmel_abdac_pdata {
+	struct dw_dma_slave	dws;
+};
+
+#endif /* __INCLUDE_SOUND_ATMEL_ABDAC_H */

sound/atmel/Kconfig

···
+menu "Atmel devices (AVR32 and AT91)"
+	depends on AVR32 || ARCH_AT91
+
+config SND_ATMEL_ABDAC
+	tristate "Atmel Audio Bitstream DAC (ABDAC) driver"
+	select SND_PCM
+	depends on DW_DMAC && AVR32
+	help
+	  ALSA sound driver for the Atmel Audio Bitstream DAC (ABDAC).
+
+endmenu

sound/atmel/Makefile

···
+snd-atmel-abdac-objs		:= abdac.o
+
+obj-$(CONFIG_SND_ATMEL_ABDAC)	+= snd-atmel-abdac.o

sound/atmel/abdac.c

···
+/*
+ * Driver for the Atmel on-chip Audio Bitstream DAC (ABDAC)
+ *
+ * Copyright (C) 2006-2009 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+#include <linux/clk.h>
+#include <linux/bitmap.h>
+#include <linux/dw_dmac.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+#include <sound/atmel-abdac.h>
+
+/* DAC register offsets */
+#define DAC_DATA                                0x0000
+#define DAC_CTRL                                0x0008
+#define DAC_INT_MASK                            0x000c
+#define DAC_INT_EN                              0x0010
+#define DAC_INT_DIS                             0x0014
+#define DAC_INT_CLR                             0x0018
+#define DAC_INT_STATUS                          0x001c
+
+/* Bitfields in CTRL */
+#define DAC_SWAP_OFFSET                         30
+#define DAC_SWAP_SIZE                           1
+#define DAC_EN_OFFSET                           31
+#define DAC_EN_SIZE                             1
+
+/* Bitfields in INT_MASK/INT_EN/INT_DIS/INT_STATUS/INT_CLR */
+#define DAC_UNDERRUN_OFFSET                     28
+#define DAC_UNDERRUN_SIZE                       1
+#define DAC_TX_READY_OFFSET                     29
+#define DAC_TX_READY_SIZE                       1
+
+/* Bit manipulation macros */
+#define DAC_BIT(name)					\
+	(1 << DAC_##name##_OFFSET)
+#define DAC_BF(name, value)				\
+	(((value) & ((1 << DAC_##name##_SIZE) - 1))	\
+	 << DAC_##name##_OFFSET)
+#define DAC_BFEXT(name, value)				\
+	(((value) >> DAC_##name##_OFFSET)		\
+	 & ((1 << DAC_##name##_SIZE) - 1))
+#define DAC_BFINS(name, value, old)			\
+	(((old) & ~(((1 << DAC_##name##_SIZE) - 1)	\
+		    << DAC_##name##_OFFSET))		\
+	 | DAC_BF(name, value))
+
+/* Register access macros */
+#define dac_readl(port, reg)				\
+	__raw_readl((port)->regs + DAC_##reg)
+#define dac_writel(port, reg, value)			\
+	__raw_writel((value), (port)->regs + DAC_##reg)
+
+/*
+ * ABDAC supports a maximum of 6 different rates from a generic clock. The
+ * generic clock has a power of two divider, which gives 6 steps from 192 kHz
+ * to 5112 Hz.
+ */
+#define MAX_NUM_RATES	6
+/* ALSA seems to use rates between 192000 Hz and 5112 Hz. */
+#define RATE_MAX	192000
+#define RATE_MIN	5112
+
+enum {
+	DMA_READY = 0,
+};
+
+struct atmel_abdac_dma {
+	struct dma_chan		*chan;
+	struct dw_cyclic_desc	*cdesc;
+};
+
+struct atmel_abdac {
+	struct clk				*pclk;
+	struct clk				*sample_clk;
+	struct platform_device			*pdev;
+	struct atmel_abdac_dma			dma;
+
+	struct snd_pcm_hw_constraint_list	constraints_rates;
+	struct snd_pcm_substream		*substream;
+	struct snd_card				*card;
+	struct snd_pcm				*pcm;
+
+	void __iomem				*regs;
+	unsigned long				flags;
+	unsigned int				rates[MAX_NUM_RATES];
+	unsigned int				rates_num;
+	int					irq;
+};
+
+#define get_dac(card) ((struct atmel_abdac *)(card)->private_data)
+
+/* This function is called by the DMA driver. */
+static void atmel_abdac_dma_period_done(void *arg)
+{
+	struct atmel_abdac *dac = arg;
+	snd_pcm_period_elapsed(dac->substream);
+}
+
+static int atmel_abdac_prepare_dma(struct atmel_abdac *dac,
+		struct snd_pcm_substream *substream,
+		enum dma_data_direction direction)
+{
+	struct dma_chan			*chan = dac->dma.chan;
+	struct dw_cyclic_desc		*cdesc;
+	struct snd_pcm_runtime		*runtime = substream->runtime;
+	unsigned long			buffer_len, period_len;
+
+	/*
+	 * We don't do DMA on "complex" transfers, i.e. with
+	 * non-halfword-aligned buffers or lengths.
+	 */
+	if (runtime->dma_addr & 1 || runtime->buffer_size & 1) {
+		dev_dbg(&dac->pdev->dev, "too complex transfer\n");
+		return -EINVAL;
+	}
+
+	buffer_len = frames_to_bytes(runtime, runtime->buffer_size);
+	period_len = frames_to_bytes(runtime, runtime->period_size);
+
+	cdesc = dw_dma_cyclic_prep(chan, runtime->dma_addr, buffer_len,
+			period_len, DMA_TO_DEVICE);
+	if (IS_ERR(cdesc)) {
+		dev_dbg(&dac->pdev->dev, "could not prepare cyclic DMA\n");
+		return PTR_ERR(cdesc);
+	}
+
+	cdesc->period_callback = atmel_abdac_dma_period_done;
+	cdesc->period_callback_param = dac;
+
+	dac->dma.cdesc = cdesc;
+
+	set_bit(DMA_READY, &dac->flags);
+
+	return 0;
+}
+
+static struct snd_pcm_hardware atmel_abdac_hw = {
+	.info			= (SNDRV_PCM_INFO_MMAP
+				  | SNDRV_PCM_INFO_MMAP_VALID
+				  | SNDRV_PCM_INFO_INTERLEAVED
+				  | SNDRV_PCM_INFO_BLOCK_TRANSFER
+				  | SNDRV_PCM_INFO_RESUME
+				  | SNDRV_PCM_INFO_PAUSE),
+	.formats		= (SNDRV_PCM_FMTBIT_S16_BE),
+	.rates			= (SNDRV_PCM_RATE_KNOT),
+	.rate_min		= RATE_MIN,
+	.rate_max		= RATE_MAX,
+	.channels_min		= 2,
+	.channels_max		= 2,
+	.buffer_bytes_max	= 64 * 4096,
+	.period_bytes_min	= 4096,
+	.period_bytes_max	= 4096,
+	.periods_min		= 4,
+	.periods_max		= 64,
+};
+
+static int atmel_abdac_open(struct snd_pcm_substream *substream)
+{
+	struct atmel_abdac *dac = snd_pcm_substream_chip(substream);
+
+	dac->substream = substream;
+	atmel_abdac_hw.rate_max = dac->rates[dac->rates_num - 1];
+	atmel_abdac_hw.rate_min = dac->rates[0];
+	substream->runtime->hw = atmel_abdac_hw;
+
+	return snd_pcm_hw_constraint_list(substream->runtime, 0,
+			SNDRV_PCM_HW_PARAM_RATE, &dac->constraints_rates);
+}
+
+static int atmel_abdac_close(struct snd_pcm_substream *substream)
+{
+	struct atmel_abdac *dac = snd_pcm_substream_chip(substream);
+	dac->substream = NULL;
+	return 0;
+}
+
+static int atmel_abdac_hw_params(struct snd_pcm_substream *substream,
+		struct snd_pcm_hw_params *hw_params)
+{
+	struct atmel_abdac *dac = snd_pcm_substream_chip(substream);
+	int retval;
+
+	retval = snd_pcm_lib_malloc_pages(substream,
+			params_buffer_bytes(hw_params));
+	if (retval < 0)
+		return retval;
+	/* snd_pcm_lib_malloc_pages returns 1 if buffer is changed. */
+	if (retval == 1)
+		if (test_and_clear_bit(DMA_READY, &dac->flags))
+			dw_dma_cyclic_free(dac->dma.chan);
+
+	return retval;
+}
+
+static int atmel_abdac_hw_free(struct snd_pcm_substream *substream)
+{
+	struct atmel_abdac *dac = snd_pcm_substream_chip(substream);
+	if (test_and_clear_bit(DMA_READY, &dac->flags))
+		dw_dma_cyclic_free(dac->dma.chan);
+	return snd_pcm_lib_free_pages(substream);
+}
+
+static int atmel_abdac_prepare(struct snd_pcm_substream *substream)
+{
+	struct atmel_abdac *dac = snd_pcm_substream_chip(substream);
+	int retval;
+
+	retval = clk_set_rate(dac->sample_clk, 256 * substream->runtime->rate);
+	if (retval)
+		return retval;
+
+	if (!test_bit(DMA_READY, &dac->flags))
+		retval = atmel_abdac_prepare_dma(dac, substream, DMA_TO_DEVICE);
+
+	return retval;
+}
+
+static int atmel_abdac_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	struct atmel_abdac *dac = snd_pcm_substream_chip(substream);
+	int retval = 0;
+
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: /* fall through */
+	case SNDRV_PCM_TRIGGER_RESUME: /* fall through */
+	case SNDRV_PCM_TRIGGER_START:
+		clk_enable(dac->sample_clk);
+		retval = dw_dma_cyclic_start(dac->dma.chan);
+		if (retval)
+			goto out;
+		dac_writel(dac, CTRL, DAC_BIT(EN));
+		break;
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH: /* fall through */
+	case SNDRV_PCM_TRIGGER_SUSPEND: /* fall through */
+	case SNDRV_PCM_TRIGGER_STOP:
+		dw_dma_cyclic_stop(dac->dma.chan);
+		dac_writel(dac, DATA, 0);
+		dac_writel(dac, CTRL, 0);
+		clk_disable(dac->sample_clk);
+		break;
+	default:
+		retval = -EINVAL;
+		break;
+	}
+out:
+	return retval;
+}
+
+static snd_pcm_uframes_t
+atmel_abdac_pointer(struct snd_pcm_substream *substream)
+{
+	struct atmel_abdac	*dac = snd_pcm_substream_chip(substream);
+	struct snd_pcm_runtime	*runtime = substream->runtime;
+	snd_pcm_uframes_t	frames;
+	unsigned long		bytes;
+
+	bytes = dw_dma_get_src_addr(dac->dma.chan);
+	bytes -= runtime->dma_addr;
+
+	frames = bytes_to_frames(runtime, bytes);
+	if (frames >= runtime->buffer_size)
+		frames -= runtime->buffer_size;
+
+	return frames;
+}
+
+static irqreturn_t abdac_interrupt(int irq, void *dev_id)
+{
+	struct atmel_abdac *dac = dev_id;
+	u32 status;
+
+	status = dac_readl(dac, INT_STATUS);
+	if (status & DAC_BIT(UNDERRUN)) {
+		dev_err(&dac->pdev->dev, "underrun detected\n");
+		dac_writel(dac, INT_CLR, DAC_BIT(UNDERRUN));
+	} else {
+		dev_err(&dac->pdev->dev, "spurious interrupt (status=0x%x)\n",
+			status);
+		dac_writel(dac, INT_CLR, status);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static struct snd_pcm_ops atmel_abdac_ops = {
+	.open		= atmel_abdac_open,
+	.close		= atmel_abdac_close,
+	.ioctl		= snd_pcm_lib_ioctl,
+	.hw_params	= atmel_abdac_hw_params,
+	.hw_free	= atmel_abdac_hw_free,
+	.prepare	= atmel_abdac_prepare,
+	.trigger	= atmel_abdac_trigger,
+	.pointer	= atmel_abdac_pointer,
+};
+
+static int __devinit atmel_abdac_pcm_new(struct atmel_abdac *dac)
+{
+	struct snd_pcm_hardware hw = atmel_abdac_hw;
+	struct snd_pcm *pcm;
+	int retval;
+
+	retval = snd_pcm_new(dac->card, dac->card->shortname,
+			dac->pdev->id, 1, 0, &pcm);
+	if (retval)
+		return retval;
+
+	strcpy(pcm->name, dac->card->shortname);
+	pcm->private_data = dac;
+	pcm->info_flags = 0;
+	dac->pcm = pcm;
+
+	snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &atmel_abdac_ops);
+
+	retval = snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,
+			&dac->pdev->dev, hw.periods_min * hw.period_bytes_min,
+			hw.buffer_bytes_max);
+
+	return retval;
+}
+
+static bool filter(struct dma_chan *chan, void *slave)
+{
+	struct dw_dma_slave *dws = slave;
+
+	if (dws->dma_dev == chan->device->dev) {
+		chan->private = dws;
+		return true;
+	} else
+		return false;
+}
+
+static int set_sample_rates(struct atmel_abdac *dac)
+{
+	long new_rate = RATE_MAX;
+	int retval = -EINVAL;
+	int index = 0;
+
+	/* we start at 192 kHz and work our way down to 5112 Hz */
+	while (new_rate >= RATE_MIN && index < (MAX_NUM_RATES + 1)) {
+		new_rate = clk_round_rate(dac->sample_clk, 256 * new_rate);
+		if (new_rate < 0)
+			break;
+		/* make sure we are below the ABDAC clock */
+		if (new_rate <= clk_get_rate(dac->pclk)) {
+			dac->rates[index] = new_rate / 256;
+			index++;
+		}
+		/* divide by 256 and then by two to get next rate */
+		new_rate /= 256 * 2;
+	}
+
+	if (index) {
+		int i;
+
+		/* reverse array, smallest go first */
+		for (i = 0; i < (index / 2); i++) {
+			unsigned int tmp = dac->rates[index - 1 - i];
+			dac->rates[index - 1 - i] = dac->rates[i];
+			dac->rates[i] = tmp;
+		}
+
+		dac->constraints_rates.count = index;
+		dac->constraints_rates.list = dac->rates;
+		dac->constraints_rates.mask = 0;
+		dac->rates_num = index;
+
+		retval = 0;
+	}
+
+	return retval;
+}
+
+static int __devinit atmel_abdac_probe(struct platform_device *pdev)
+{
+	struct snd_card		*card;
+	struct atmel_abdac	*dac;
+	struct resource		*regs;
+	struct atmel_abdac_pdata	*pdata;
+	struct clk		*pclk;
+	struct clk		*sample_clk;
+	int			retval;
+	int			irq;
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!regs) {
+		dev_dbg(&pdev->dev, "no memory resource\n");
+		return -ENXIO;
+	}
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_dbg(&pdev->dev, "could not get IRQ number\n");
+		return irq;
+	}
+
+	pdata = pdev->dev.platform_data;
+	if (!pdata) {
+		dev_dbg(&pdev->dev, "no platform data\n");
+		return -ENXIO;
+	}
+
+	pclk = clk_get(&pdev->dev, "pclk");
+	if (IS_ERR(pclk)) {
+		dev_dbg(&pdev->dev, "no peripheral clock\n");
+		return PTR_ERR(pclk);
+	}
+	sample_clk = clk_get(&pdev->dev, "sample_clk");
+	if (IS_ERR(pclk)) {
+		dev_dbg(&pdev->dev, "no sample clock\n");
+		retval = PTR_ERR(pclk);
+		goto out_put_pclk;
+	}
+	clk_enable(pclk);
+
+	retval = snd_card_create(SNDRV_DEFAULT_IDX1, SNDRV_DEFAULT_STR1,
+			THIS_MODULE, sizeof(struct atmel_abdac), &card);
+	if (retval) {
+		dev_dbg(&pdev->dev, "could not create sound card device\n");
+		goto out_put_sample_clk;
+	}
+
+	dac = get_dac(card);
+
+	dac->irq = irq;
+	dac->card = card;
+	dac->pclk = pclk;
+	dac->sample_clk = sample_clk;
+	dac->pdev = pdev;
+
+	retval = set_sample_rates(dac);
+	if (retval < 0) {
+		dev_dbg(&pdev->dev, "could not set supported rates\n");
+		goto out_free_card;
+	}
+
+	dac->regs = ioremap(regs->start, regs->end - regs->start + 1);
+	if (!dac->regs) {
+		dev_dbg(&pdev->dev, "could not remap register memory\n");
+		goto out_free_card;
+	}
+
+	/* make sure the DAC is silent and disabled */
+	dac_writel(dac, DATA, 0);
+	dac_writel(dac, CTRL, 0);
+
+	retval = request_irq(irq, abdac_interrupt, 0, "abdac", dac);
+	if (retval) {
+		dev_dbg(&pdev->dev, "could not request irq\n");
+		goto out_unmap_regs;
+	}
+
+	snd_card_set_dev(card, &pdev->dev);
+
+	if (pdata->dws.dma_dev) {
+		struct dw_dma_slave *dws = &pdata->dws;
+		dma_cap_mask_t mask;
+
+		dws->tx_reg = regs->start + DAC_DATA;
+
+		dma_cap_zero(mask);
+		dma_cap_set(DMA_SLAVE, mask);
+
+		dac->dma.chan = dma_request_channel(mask, filter, dws);
+	}
+	if (!pdata->dws.dma_dev || !dac->dma.chan) {
+		dev_dbg(&pdev->dev, "DMA not available\n");
+		retval = -ENODEV;
+		goto out_unset_card_dev;
+	}
+
+	strcpy(card->driver, "Atmel ABDAC");
+	strcpy(card->shortname, "Atmel ABDAC");
+	sprintf(card->longname, "Atmel Audio Bitstream DAC");
+
+	retval = atmel_abdac_pcm_new(dac);
+	if (retval) {
+		dev_dbg(&pdev->dev, "could not register ABDAC pcm device\n");
+		goto out_release_dma;
+	}
+
+	retval = snd_card_register(card);
+	if (retval) {
+		dev_dbg(&pdev->dev, "could not register sound card\n");
+		goto out_release_dma;
+	}
+
+	platform_set_drvdata(pdev, card);
+
+	dev_info(&pdev->dev, "Atmel ABDAC at 0x%p using %s\n",
+			dac->regs, dac->dma.chan->dev->device.bus_id);
+
+	return retval;
+
+out_release_dma:
+	dma_release_channel(dac->dma.chan);
+	dac->dma.chan = NULL;
+out_unset_card_dev:
+	snd_card_set_dev(card, NULL);
+	free_irq(irq, dac);
+out_unmap_regs:
+	iounmap(dac->regs);
+out_free_card:
+	snd_card_free(card);
+out_put_sample_clk:
+	clk_put(sample_clk);
+	clk_disable(pclk);
+out_put_pclk:
+	clk_put(pclk);
+	return retval;
+}
+
+#ifdef CONFIG_PM
+static int atmel_abdac_suspend(struct platform_device *pdev, pm_message_t msg)
+{
+	struct snd_card *card = platform_get_drvdata(pdev);
+	struct atmel_abdac *dac = card->private_data;
+
+	dw_dma_cyclic_stop(dac->dma.chan);
+	clk_disable(dac->sample_clk);
+	clk_disable(dac->pclk);
+
+	return 0;
+}
+
+static int atmel_abdac_resume(struct platform_device *pdev)
+{
+	struct snd_card *card = platform_get_drvdata(pdev);
+	struct atmel_abdac *dac = card->private_data;
+
+	clk_enable(dac->pclk);
+	clk_enable(dac->sample_clk);
+	if (test_bit(DMA_READY, &dac->flags))
+		dw_dma_cyclic_start(dac->dma.chan);
+
+	return 0;
+}
+#else
+#define atmel_abdac_suspend NULL
+#define atmel_abdac_resume NULL
+#endif
+
+static int __devexit atmel_abdac_remove(struct platform_device *pdev)
+{
+	struct snd_card *card = platform_get_drvdata(pdev);
+	struct atmel_abdac *dac = get_dac(card);
+
+	clk_put(dac->sample_clk);
+	clk_disable(dac->pclk);
+	clk_put(dac->pclk);
+
+	dma_release_channel(dac->dma.chan);
+	dac->dma.chan = NULL;
+	snd_card_set_dev(card, NULL);
+	iounmap(dac->regs);
+	free_irq(dac->irq, dac);
+	snd_card_free(card);
+
+	platform_set_drvdata(pdev, NULL);
+
+	return 0;
+}
+
+static struct platform_driver atmel_abdac_driver = {
+	.remove		= __devexit_p(atmel_abdac_remove),
+	.driver		= {
+		.name	= "atmel_abdac",
+	},
+	.suspend	= atmel_abdac_suspend,
+	.resume		= atmel_abdac_resume,
+};
+
+static int __init atmel_abdac_init(void)
+{
+	return platform_driver_probe(&atmel_abdac_driver,
+			atmel_abdac_probe);
+}
+module_init(atmel_abdac_init);
+
+static void __exit atmel_abdac_exit(void)
+{
+	platform_driver_unregister(&atmel_abdac_driver);
+}
+module_exit(atmel_abdac_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Driver for Atmel Audio Bitstream DAC (ABDAC)");
+MODULE_AUTHOR("Hans-Christian Egtvedt <[e-mail]>");