Re: [PATCH v3 2/2] ASoC: mchp-spdiftx: add driver for S/PDIF TX Controller

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On 03.08.2020 19:11, Codrin Ciubotariu - M19940 wrote:
> On 03.08.2020 16:06, Claudiu Beznea - M18063 wrote:
>>
>>
>> On 03.08.2020 11:18, Codrin Ciubotariu wrote:
>>> The new SPDIF TX controller is a serial port compliant with the IEC-
>>> 60958 standard. It also supports programmable User Data and Channel
>>> Status fields.
>>>
>>> This IP is embedded in Microchip's sama7g5 SoC.
>>>
>>> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
>>> ---
>>>
>>> Changes in v2, v3:
>>>   - none;
>>>
>>>   sound/soc/atmel/Kconfig        |  12 +
>>>   sound/soc/atmel/Makefile       |   2 +
>>>   sound/soc/atmel/mchp-spdiftx.c | 864 +++++++++++++++++++++++++++++++++
>>>   3 files changed, 878 insertions(+)
>>>   create mode 100644 sound/soc/atmel/mchp-spdiftx.c
>>>
>>> diff --git a/sound/soc/atmel/Kconfig b/sound/soc/atmel/Kconfig
>>> index 71f2d42188c4..93beb7d670a3 100644
>>> --- a/sound/soc/atmel/Kconfig
>>> +++ b/sound/soc/atmel/Kconfig
>>> @@ -132,4 +132,16 @@ config SND_MCHP_SOC_I2S_MCC
>>>   	  and supports a Time Division Multiplexed (TDM) interface with
>>>   	  external multi-channel audio codecs.
>>>   
>>> +config SND_MCHP_SOC_SPDIFTX
>>> +	tristate "Microchip ASoC driver for boards using S/PDIF TX"
>>> +	depends on OF && (ARCH_AT91 || COMPILE_TEST)
>>> +	select SND_SOC_GENERIC_DMAENGINE_PCM
>>> +	select REGMAP_MMIO
>>> +	help
>>> +	  Say Y or M if you want to add support for Microchip S/PDIF TX ASoc
>>> +	  driver on the following Microchip platforms:
>>> +	  - sama7g5
>>> +
>>> +	  This S/PDIF TX driver is compliant with IEC-60958 standard and
>>> +	  includes programable User Data and Channel Status fields.
>>>   endif
>>> diff --git a/sound/soc/atmel/Makefile b/sound/soc/atmel/Makefile
>>> index c7d2989791be..3fd89a0063df 100644
>>> --- a/sound/soc/atmel/Makefile
>>> +++ b/sound/soc/atmel/Makefile
>>> @@ -5,6 +5,7 @@ snd-soc-atmel-pcm-dma-objs := atmel-pcm-dma.o
>>>   snd-soc-atmel_ssc_dai-objs := atmel_ssc_dai.o
>>>   snd-soc-atmel-i2s-objs := atmel-i2s.o
>>>   snd-soc-mchp-i2s-mcc-objs := mchp-i2s-mcc.o
>>> +snd-soc-mchp-spdiftx-objs := mchp-spdiftx.o
>>>   
>>>   # pdc and dma need to both be built-in if any user of
>>>   # ssc is built-in.
>>> @@ -17,6 +18,7 @@ endif
>>>   obj-$(CONFIG_SND_ATMEL_SOC_SSC) += snd-soc-atmel_ssc_dai.o
>>>   obj-$(CONFIG_SND_ATMEL_SOC_I2S) += snd-soc-atmel-i2s.o
>>>   obj-$(CONFIG_SND_MCHP_SOC_I2S_MCC) += snd-soc-mchp-i2s-mcc.o
>>> +obj-$(CONFIG_SND_MCHP_SOC_SPDIFTX) += snd-soc-mchp-spdiftx.o
>>>   
>>>   # AT91 Machine Support
>>>   snd-soc-sam9g20-wm8731-objs := sam9g20_wm8731.o
>>> diff --git a/sound/soc/atmel/mchp-spdiftx.c b/sound/soc/atmel/mchp-spdiftx.c
>>> new file mode 100644
>>> index 000000000000..738f6788212e
>>> --- /dev/null
>>> +++ b/sound/soc/atmel/mchp-spdiftx.c
>>> @@ -0,0 +1,864 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +//
>>> +// Driver for Microchip S/PDIF TX Controller
>>> +//
>>> +// Copyright (C) 2020 Microchip Technology Inc. and its subsidiaries
>>> +//
>>> +// Author: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
>>> +
>>> +#include <linux/clk.h>
>>> +#include <linux/io.h>
>>> +#include <linux/module.h>
>>> +#include <linux/spinlock.h>
>>> +
>>> +#include <sound/asoundef.h>
>>> +#include <sound/dmaengine_pcm.h>
>>> +#include <sound/pcm_params.h>
>>> +#include <sound/soc.h>
>>> +
>>> +/*
>>> + * ---- S/PDIF Transmitter Controller Register map ----
>>> + */
>>> +#define SPDIFTX_CR			0x00	/* Control Register */
>>> +#define SPDIFTX_MR			0x04	/* Mode Register */
>>
>> This register is read/write either in atomic and non-atomic contextes but
>> not protected everywhere the same way.
> 
> I only need the TXEN bit from this register in an atomic context, this 
> is why there are also non-atomic contexts.
> 
>>
>>> +#define SPDIFTX_CDR			0x0C	/* Common Data Register */
>>> +
>>> +#define SPDIFTX_IER			0x14	/* Interrupt Enable Register */
>>> +#define SPDIFTX_IDR			0x18	/* Interrupt Disable Register */
>>> +#define SPDIFTX_IMR			0x1C	/* Interrupt Mask Register */
>>> +#define SPDIFTX_ISR			0x20	/* Interrupt Status Register */
>>> +
>>> +#define SPDIFTX_CH1UD(reg)	(0x50 + (reg) * 4)	/* User Data 1 Register x */
>>> +#define SPDIFTX_CH1S(reg)	(0x80 + (reg) * 4)	/* Channel Status 1 Register x */
>>> +
>>> +#define SPDIFTX_VERSION			0xF0
>>> +
>>> +/*
>>> + * ---- Control Register (Write-only) ----
>>> + */
>>> +#define SPDIFTX_CR_SWRST		BIT(0)	/* Software Reset */
>>> +#define SPDIFTX_CR_FCLR			BIT(1)	/* FIFO clear */
>>> +
>>> +/*
>>> + * ---- Mode Register (Read/Write) ----
>>> + */
>>> +/* Transmit Enable */
>>> +#define SPDIFTX_MR_TXEN_MASK		GENMASK(0, 0)
>>> +#define SPDIFTX_MR_TXEN_DISABLE		(0 << 0)
>>> +#define SPDIFTX_MR_TXEN_ENABLE		(1 << 0)
>>> +
>>> +/* Multichannel Transfer */
>>> +#define SPDIFTX_MR_MULTICH_MASK		GENAMSK(1, 1)
>>> +#define SPDIFTX_MR_MULTICH_MONO		(0 << 1)
>>> +#define SPDIFTX_MR_MULTICH_DUAL		(1 << 1)
>>> +
>>> +/* Data Word Endian Mode */
>>> +#define SPDIFTX_MR_ENDIAN_MASK		GENMASK(2, 2)
>>> +#define SPDIFTX_MR_ENDIAN_LITTLE	(0 << 2)
>>> +#define SPDIFTX_MR_ENDIAN_BIG		(1 << 2)
>>> +
>>> +/* Data Justification */
>>> +#define SPDIFTX_MR_JUSTIFY_MASK		GENMASK(3, 3)
>>> +#define SPDIFTX_MR_JUSTIFY_LSB		(0 << 3)
>>> +#define SPDIFTX_MR_JUSTIFY_MSB		(1 << 3)
>>> +
>>> +/* Common Audio Register Transfer Mode */
>>> +#define SPDIFTX_MR_CMODE_MASK			GENMASK(5, 4)
>>> +#define SPDIFTX_MR_CMODE_INDEX_ACCESS		(0 << 4)
>>> +#define SPDIFTX_MR_CMODE_TOGGLE_ACCESS		(1 << 4)
>>> +#define SPDIFTX_MR_CMODE_INTERLVD_ACCESS	(2 << 4)
>>> +
>>> +/* Valid Bits per Sample */
>>> +#define SPDIFTX_MR_VBPS_MASK		GENMASK(13, 8)
>>> +#define SPDIFTX_MR_VBPS(bps)		(((bps) << 8) & SPDIFTX_MR_VBPS_MASK)
>>> +
>>> +/* Chunk Size */
>>> +#define SPDIFTX_MR_CHUNK_MASK		GENMASK(19, 16)
>>> +#define SPDIFTX_MR_CHUNK(size)		(((size) << 16) & SPDIFTX_MR_CHUNK_MASK)
>>> +
>>> +/* Validity Bits for Channels 1 and 2 */
>>> +#define SPDIFTX_MR_VALID1			BIT(24)
>>> +#define SPDIFTX_MR_VALID2			BIT(25)
>>> +
>>> +/* Disable Null Frame on underrrun */
>>> +#define SPDIFTX_MR_DNFR_MASK		GENMASK(27, 27)
>>> +#define SPDIFTX_MR_DNFR_INVALID		(0 << 27)
>>> +#define SPDIFTX_MR_DNFR_VALID		(1 << 27)
>>> +
>>> +/* Bytes per Sample */
>>> +#define SPDIFTX_MR_BPS_MASK		GENMASK(29, 28)
>>> +#define SPDIFTX_MR_BPS(bytes) \
>>> +	((((bytes) - 1) << 28) & SPDIFTX_MR_BPS_MASK)
>>> +
>>> +/*
>>> + * ---- Interrupt Enable/Disable/Mask/Status Register (Write/Read-only) ----
>>> + */
>>> +#define SPDIFTX_IR_TXRDY		BIT(0)
>>> +#define SPDIFTX_IR_TXEMPTY		BIT(1)
>>> +#define SPDIFTX_IR_TXFULL		BIT(2)
>>> +#define SPDIFTX_IR_TXCHUNK		BIT(3)
>>> +#define SPDIFTX_IR_TXUDR		BIT(4)
>>> +#define SPDIFTX_IR_TXOVR		BIT(5)
>>> +#define SPDIFTX_IR_CSRDY		BIT(6)
>>> +#define SPDIFTX_IR_UDRDY		BIT(7)
>>> +#define SPDIFTX_IR_TXRDYCH(ch)		BIT((ch) + 8)
>>> +#define SPDIFTX_IR_SECE			BIT(10)
>>> +#define SPDIFTX_IR_TXUDRCH(ch)		BIT((ch) + 11)
>>> +#define SPDIFTX_IR_BEND			BIT(13)
>>> +
>>> +static bool mchp_spdiftx_readable_reg(struct device *dev, unsigned int reg)
>>> +{
>>> +	switch (reg) {
>>> +	case SPDIFTX_MR:
>>> +	case SPDIFTX_IMR:
>>> +	case SPDIFTX_ISR:
>>> +	case SPDIFTX_CH1UD(0):
>>> +	case SPDIFTX_CH1UD(1):
>>> +	case SPDIFTX_CH1UD(2):
>>> +	case SPDIFTX_CH1UD(3):
>>> +	case SPDIFTX_CH1UD(4):
>>> +	case SPDIFTX_CH1UD(5):
>>> +	case SPDIFTX_CH1S(0):
>>> +	case SPDIFTX_CH1S(1):
>>> +	case SPDIFTX_CH1S(2):
>>> +	case SPDIFTX_CH1S(3):
>>> +	case SPDIFTX_CH1S(4):
>>> +	case SPDIFTX_CH1S(5):
>>> +		return true;
>>> +	default:
>>> +		return false;
>>> +	}
>>> +}
>>> +
>>> +static bool mchp_spdiftx_writeable_reg(struct device *dev, unsigned int reg)
>>> +{
>>> +	switch (reg) {
>>> +	case SPDIFTX_CR:
>>> +	case SPDIFTX_MR:
>>> +	case SPDIFTX_CDR:
>>> +	case SPDIFTX_IER:
>>> +	case SPDIFTX_IDR:
>>> +	case SPDIFTX_CH1UD(0):
>>> +	case SPDIFTX_CH1UD(1):
>>> +	case SPDIFTX_CH1UD(2):
>>> +	case SPDIFTX_CH1UD(3):
>>> +	case SPDIFTX_CH1UD(4):
>>> +	case SPDIFTX_CH1UD(5):
>>> +	case SPDIFTX_CH1S(0):
>>> +	case SPDIFTX_CH1S(1):
>>> +	case SPDIFTX_CH1S(2):
>>> +	case SPDIFTX_CH1S(3):
>>> +	case SPDIFTX_CH1S(4):
>>> +	case SPDIFTX_CH1S(5):
>>> +		return true;
>>> +	default:
>>> +		return false;
>>> +	}
>>> +}
>>> +
>>> +static bool mchp_spdiftx_precious_reg(struct device *dev, unsigned int reg)
>>> +{
>>> +	switch (reg) {
>>> +	case SPDIFTX_CDR:
>>> +	case SPDIFTX_ISR:
>>> +		return true;
>>> +	default:
>>> +		return false;
>>> +	}
>>> +}
>>> +
>>> +static const struct regmap_config mchp_spdiftx_regmap_config = {
>>> +	.reg_bits = 32,
>>> +	.reg_stride = 4,
>>> +	.val_bits = 32,
>>> +	.max_register = SPDIFTX_VERSION,
>>> +	.readable_reg = mchp_spdiftx_readable_reg,
>>> +	.writeable_reg = mchp_spdiftx_writeable_reg,
>>> +	.precious_reg = mchp_spdiftx_precious_reg,
>>> +};
>>> +
>>> +#define SPDIFTX_GCLK_RATIO	128
>>> +
>>> +#define SPDIFTX_CS_BITS		192
>>> +#define SPDIFTX_UD_BITS		192
>>> +
>>> +struct mchp_spdiftx_mixer_control {
>>> +	unsigned char				ch_stat[SPDIFTX_CS_BITS / 8];
>>> +	unsigned char				user_data[SPDIFTX_UD_BITS / 8];
>>> +	spinlock_t				lock;
>>> +};
>>> +
>>> +struct mchp_spdiftx_dev {
>>> +	struct mchp_spdiftx_mixer_control	control;
>>> +	struct snd_dmaengine_dai_dma_data	playback;
>>> +	struct device				*dev;
>>> +	struct regmap				*regmap;
>>> +	struct clk				*pclk;
>>> +	struct clk				*gclk;
>>> +	unsigned int				fmt;
>>> +	const struct mchp_i2s_caps		*caps;
>>> +	int					gclk_enabled:1;
>>> +};
>>> +
>>> +static inline int mchp_spdiftx_is_running(struct mchp_spdiftx_dev *dev)
>>> +{
>>> +	u32 mr;
>>> +
>>> +	regmap_read(dev->regmap, SPDIFTX_MR, &mr);
>>> +	return !!(mr & SPDIFTX_MR_TXEN_ENABLE);
>>> +}
>>> +
>>> +static void mchp_spdiftx_channel_status_write(struct mchp_spdiftx_dev *dev)
>>> +{
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	u32 val;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < ARRAY_SIZE(ctrl->ch_stat) / 4; i++) {
>>> +		val = (ctrl->ch_stat[(i * 4) + 0] << 0) |
>>> +		      (ctrl->ch_stat[(i * 4) + 1] << 8) |
>>> +		      (ctrl->ch_stat[(i * 4) + 2] << 16) |
>>> +		      (ctrl->ch_stat[(i * 4) + 3] << 24);
>>> +
>>> +		regmap_write(dev->regmap, SPDIFTX_CH1S(i), val);
>>> +	}
>>> +}
>>> +
>>> +static void mchp_spdiftx_user_data_write(struct mchp_spdiftx_dev *dev)
>>> +{
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	u32 val;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < ARRAY_SIZE(ctrl->user_data) / 4; i++) {
>>> +		val = (ctrl->user_data[(i * 4) + 0] << 0) |
>>> +		      (ctrl->user_data[(i * 4) + 1] << 8) |
>>> +		      (ctrl->user_data[(i * 4) + 2] << 16) |
>>> +		      (ctrl->user_data[(i * 4) + 3] << 24);
>>> +
>>> +		regmap_write(dev->regmap, SPDIFTX_CH1UD(i), val);
>>> +	}
>>> +}
>>> +
>>> +static irqreturn_t mchp_spdiftx_interrupt(int irq, void *dev_id)
>>> +{
>>> +	struct mchp_spdiftx_dev *dev = dev_id;
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	u32 sr, imr, pending, idr = 0;
>>> +
>>> +	regmap_read(dev->regmap, SPDIFTX_ISR, &sr);
>>> +	regmap_read(dev->regmap, SPDIFTX_IMR, &imr);
>>> +	pending = sr & imr;
>>> +
>>> +	if (!pending)
>>> +		return IRQ_NONE;
>>> +
>>> +	if (pending & SPDIFTX_IR_TXUDR) {
>>> +		dev_warn(dev->dev, "underflow detected\n");
>>> +		idr |= SPDIFTX_IR_TXUDR;
>>> +	}
>>> +
>>> +	if (pending & SPDIFTX_IR_TXOVR) {
>>> +		dev_warn(dev->dev, "overflow detected\n");
>>> +		idr |= SPDIFTX_IR_TXOVR;
>>> +	}
>>> +
>>> +	if (pending & SPDIFTX_IR_UDRDY) {
>>> +		spin_lock(&ctrl->lock);
>>> +		mchp_spdiftx_user_data_write(dev);
>>> +		spin_unlock(&ctrl->lock);
>>> +		idr |= SPDIFTX_IR_UDRDY;
>>> +	}
>>> +
>>> +	if (pending & SPDIFTX_IR_CSRDY) {
>>> +		spin_lock(&ctrl->lock);
>>> +		mchp_spdiftx_channel_status_write(dev);
>>> +		spin_unlock(&ctrl->lock);
>>> +		idr |= SPDIFTX_IR_CSRDY;
>>> +	}
>>> +
>>> +	regmap_write(dev->regmap, SPDIFTX_IDR, idr);
>>> +
>>> +	return IRQ_HANDLED;
>>> +}
>>> +
>>> +static int mchp_spdiftx_dai_startup(struct snd_pcm_substream *substream,
>>> +				    struct snd_soc_dai *dai)
>>> +{
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +	int err;
>>> +
>>> +	err = clk_prepare_enable(dev->pclk);
>>> +	if (err) {
>>> +		dev_err(dev->dev,
>>> +			"failed to enable the peripheral clock: %d\n", err);
>>> +		return err;
>>> +	}
>>> +
>>> +	/* Software reset the IP */
>>> +	regmap_write(dev->regmap, SPDIFTX_CR,
>>> +		     SPDIFTX_CR_SWRST | SPDIFTX_CR_FCLR);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static void mchp_spdiftx_dai_shutdown(struct snd_pcm_substream *substream,
>>> +				      struct snd_soc_dai *dai)
>>> +{
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +
>>> +	/* Disable interrupts */
>>> +	regmap_write(dev->regmap, SPDIFTX_IDR, 0xffffffff);
>>> +
>>> +	clk_disable_unprepare(dev->pclk);
>>> +}
>>> +
>>> +static int mchp_spdiftx_trigger(struct snd_pcm_substream *substream, int cmd,
>>> +				struct snd_soc_dai *dai)
>>> +{
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	u32 mr;
>>> +	int running;
>>> +	int ret;
>>> +
>>> +	/* do not start/stop while channel status or user data is updated */
>>> +	spin_lock(&ctrl->lock);
>>> +	regmap_read(dev->regmap, SPDIFTX_MR, &mr);
>>
>> Here, atomic, for instance.
> 
> This is where I check and change for TXEN. The IP must not be started 
> while the userspace updates the SPDIFTX_CH1UDx or SPDIFTX_CH1Sx registers.
> 
>>
>>> +	running = !!(mr & SPDIFTX_MR_TXEN_ENABLE);
>>> +
>>> +	switch (cmd) {
>>> +	case SNDRV_PCM_TRIGGER_START:
>>> +	case SNDRV_PCM_TRIGGER_RESUME:
>>> +	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
>>> +		if (!running) {
>>> +			mr &= ~SPDIFTX_MR_TXEN_MASK;
>>> +			mr |= SPDIFTX_MR_TXEN_ENABLE;
>>> +		}
>>> +		break;
>>> +	case SNDRV_PCM_TRIGGER_STOP:
>>> +	case SNDRV_PCM_TRIGGER_SUSPEND:
>>> +	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
>>> +		if (running) {
>>> +			mr &= ~SPDIFTX_MR_TXEN_MASK;
>>> +			mr |= SPDIFTX_MR_TXEN_DISABLE;
>>> +		}
>>> +		break;
>>> +	default:
>>> +		spin_unlock(&ctrl->lock);
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	ret = regmap_write(dev->regmap, SPDIFTX_MR, mr);
>>> +	spin_unlock(&ctrl->lock);
>>> +	if (ret) {
>>> +		dev_err(dev->dev, "unable to disable TX: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int mchp_spdiftx_hw_params(struct snd_pcm_substream *substream,
>>> +				  struct snd_pcm_hw_params *params,
>>> +				  struct snd_soc_dai *dai)
>>> +{
>>> +	unsigned long flags;
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	u32 mr;
>>> +	unsigned int bps = params_physical_width(params) / 8;
>>> +	int ret;
>>> +
>>> +	dev_dbg(dev->dev, "%s() rate=%u format=%#x width=%u channels=%u\n",
>>> +		__func__, params_rate(params), params_format(params),
>>> +		params_width(params), params_channels(params));
>>> +
>>> +	if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
>>> +		dev_err(dev->dev, "Capture is not supported\n");
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	regmap_read(dev->regmap, SPDIFTX_MR, &mr);
>>
>> Here non-atomic.
> 
> TXEN is not toutched here and hw_params() and trigger() callbacks can't 
> be called at the same time. 

Can mchp_spdiftx_hw_params() be suspended right after this regmap_read()
then mchp_spdiftx_trigger() to be scheduled, to set the enable bit, then
mchp_spdiftx_hw_params() to be rescheduled and after this the enable bit to
be actually set in the registers but mchp_spdiftx_hw_params() to work with
the old value? Would it be an issue if this could happen?

> The concurency can be only with the controls 
> functions, who don't touch the SPDIFTX_MR register at all.
> 
>>
>>> +
>>> +	if (mr & SPDIFTX_MR_TXEN_ENABLE) {
>>> +		dev_err(dev->dev, "PCM already running\n");
>>> +		return -EBUSY;
>>> +	}
>>> +
>>> +	/* Defaults: Toggle mode, justify to LSB, chunksize 1 */
>>> +	mr = SPDIFTX_MR_CMODE_TOGGLE_ACCESS | SPDIFTX_MR_JUSTIFY_LSB;
>>> +	dev->playback.maxburst = 1;
>>> +	switch (params_channels(params)) {
>>> +	case 1:
>>> +		mr |= SPDIFTX_MR_MULTICH_MONO;
>>> +		break;
>>> +	case 2:
>>> +		mr |= SPDIFTX_MR_MULTICH_DUAL;
>>> +		if (bps > 2)
>>> +			dev->playback.maxburst = 2;
>>> +		break;
>>> +	default:
>>> +		dev_err(dev->dev, "unsupported number of channels: %d\n",
>>> +			params_channels(params));
>>> +		return -EINVAL;
>>> +	}
>>> +	mr |= SPDIFTX_MR_CHUNK(dev->playback.maxburst);
>>> +
>>> +	switch (params_format(params)) {
>>> +	case SNDRV_PCM_FORMAT_S8:
>>> +		mr |= SPDIFTX_MR_VBPS(8);
>>> +		break;
>>> +	case SNDRV_PCM_FORMAT_S16_BE:
>>> +		mr |= SPDIFTX_MR_ENDIAN_BIG;
>>> +		fallthrough;
>>> +	case SNDRV_PCM_FORMAT_S16_LE:
>>> +		mr |= SPDIFTX_MR_VBPS(16);
>>> +		break;
>>> +	case SNDRV_PCM_FORMAT_S18_3BE:
>>> +		mr |= SPDIFTX_MR_ENDIAN_BIG;
>>> +		fallthrough;
>>> +	case SNDRV_PCM_FORMAT_S18_3LE:
>>> +		mr |= SPDIFTX_MR_VBPS(18);
>>> +		break;
>>> +	case SNDRV_PCM_FORMAT_S20_3BE:
>>> +		mr |= SPDIFTX_MR_ENDIAN_BIG;
>>> +		fallthrough;
>>> +	case SNDRV_PCM_FORMAT_S20_3LE:
>>> +		mr |= SPDIFTX_MR_VBPS(20);
>>> +		break;
>>> +	case SNDRV_PCM_FORMAT_S24_3BE:
>>> +		mr |= SPDIFTX_MR_ENDIAN_BIG;
>>> +		fallthrough;
>>> +	case SNDRV_PCM_FORMAT_S24_3LE:
>>> +		mr |= SPDIFTX_MR_VBPS(24);
>>> +		break;
>>> +	case SNDRV_PCM_FORMAT_S24_BE:
>>> +		mr |= SPDIFTX_MR_ENDIAN_BIG;
>>> +		fallthrough;
>>> +	case SNDRV_PCM_FORMAT_S24_LE:
>>> +		mr |= SPDIFTX_MR_VBPS(24);
>>> +		break;
>>> +	case SNDRV_PCM_FORMAT_S32_BE:
>>> +		mr |= SPDIFTX_MR_ENDIAN_BIG;
>>> +		fallthrough;
>>> +	case SNDRV_PCM_FORMAT_S32_LE:
>>> +		mr |= SPDIFTX_MR_VBPS(32);
>>> +		break;
>>> +	default:
>>> +		dev_err(dev->dev, "unsupported PCM format: %d\n",
>>> +			params_format(params));
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	mr |= SPDIFTX_MR_BPS(bps);
>>> +
>>> +	spin_lock_irqsave(&ctrl->lock, flags);
>>> +	ctrl->ch_stat[3] &= ~IEC958_AES3_CON_FS;
>>> +	switch (params_rate(params)) {
>>> +	case 22050:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_22050;
>>> +		break;
>>> +	case 24000:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_24000;
>>> +		break;
>>> +	case 32000:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_32000;
>>> +		break;
>>> +	case 44100:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_44100;
>>> +		break;
>>> +	case 48000:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_48000;
>>> +		break;
>>> +	case 88200:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_88200;
>>> +		break;
>>> +	case 96000:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_96000;
>>> +		break;
>>> +	case 176400:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_176400;
>>> +		break;
>>> +	case 192000:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_192000;
>>> +		break;
>>> +	case 8000:
>>> +	case 11025:
>>> +	case 16000:
>>> +	case 64000:
>>> +		ctrl->ch_stat[3] |= IEC958_AES3_CON_FS_NOTID;
>>> +		break;
>>> +	default:
>>> +		dev_err(dev->dev, "unsupported sample frequency: %u\n",
>>> +			params_rate(params));
>>> +		spin_unlock_irqrestore(&ctrl->lock, flags);
>>> +		return -EINVAL;
>>> +	}
>>> +	mchp_spdiftx_channel_status_write(dev);
>>> +	spin_unlock_irqrestore(&ctrl->lock, flags);
>>> +	mr |= SPDIFTX_MR_VALID1 | SPDIFTX_MR_VALID2;
>>> +
>>> +	if (dev->gclk_enabled) {
>>> +		clk_disable_unprepare(dev->gclk);
>>> +		dev->gclk_enabled = 0;
>>> +	}
>>> +	ret = clk_set_rate(dev->gclk, params_rate(params) *
>>> +				      SPDIFTX_GCLK_RATIO);
>>> +	if (ret) {
>>> +		dev_err(dev->dev,
>>> +			"unable to change gclk rate to: rate %u * ratio %u\n",
>>> +			params_rate(params), SPDIFTX_GCLK_RATIO);
>>> +		return ret;
>>> +	}
>>> +	ret = clk_prepare_enable(dev->gclk);
>>> +	if (ret) {
>>> +		dev_err(dev->dev, "unable to enable gclk: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +	dev->gclk_enabled = 1;
>>> +	dev_dbg(dev->dev, "%s(): GCLK set to %d\n", __func__,
>>> +		params_rate(params) * SPDIFTX_GCLK_RATIO);
>>> +
>>> +	/* Enable interrupts */
>>> +	regmap_write(dev->regmap, SPDIFTX_IER,
>>> +		     SPDIFTX_IR_TXUDR | SPDIFTX_IR_TXOVR);
>>> +
>>> +	regmap_write(dev->regmap, SPDIFTX_MR, mr);
>>
>> Same here.
> 
> I explained above. Even if MR register is changed here, the TXEN bit is 
> not changed and the previous value is kept.
> 
> The purpose of this lock is to assure that the IP won't change its state 
> (TXEN changed) while SPDIFTX_CH1UDx or SPDIFTX_CH1Sx registers are 
> updated. The lock is not to protect all the values from the MR register. 
> If you found a case in which this is not achieved, please let me know.
> 
> Thank you for your review!
> 
> Best regards,
> Codrin
> 
>>
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int mchp_spdiftx_hw_free(struct snd_pcm_substream *substream,
>>> +				struct snd_soc_dai *dai)
>>> +{
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +
>>> +	regmap_write(dev->regmap, SPDIFTX_IDR,
>>> +		     SPDIFTX_IR_TXUDR | SPDIFTX_IR_TXOVR);
>>> +	if (dev->gclk_enabled) {
>>> +		clk_disable_unprepare(dev->gclk);
>>> +		dev->gclk_enabled = 0;
>>> +	}
>>> +
>>> +	return regmap_write(dev->regmap, SPDIFTX_CR,
>>> +			    SPDIFTX_CR_SWRST | SPDIFTX_CR_FCLR);
>>> +}
>>> +
>>> +
>>> +static const struct snd_soc_dai_ops mchp_spdiftx_dai_ops = {
>>> +	.startup	= mchp_spdiftx_dai_startup,
>>> +	.shutdown	= mchp_spdiftx_dai_shutdown,
>>> +	.trigger	= mchp_spdiftx_trigger,
>>> +	.hw_params	= mchp_spdiftx_hw_params,
>>> +	.hw_free	= mchp_spdiftx_hw_free,
>>> +};
>>> +
>>> +#define MCHP_SPDIFTX_RATES	SNDRV_PCM_RATE_8000_192000
>>> +
>>> +#define MCHP_SPDIFTX_FORMATS	(SNDRV_PCM_FMTBIT_S8 |		\
>>> +				 SNDRV_PCM_FMTBIT_S16_LE |	\
>>> +				 SNDRV_PCM_FMTBIT_U16_BE |	\
>>> +				 SNDRV_PCM_FMTBIT_S18_3LE |	\
>>> +				 SNDRV_PCM_FMTBIT_S18_3BE |	\
>>> +				 SNDRV_PCM_FMTBIT_S20_3LE |	\
>>> +				 SNDRV_PCM_FMTBIT_S20_3BE |	\
>>> +				 SNDRV_PCM_FMTBIT_S24_3LE |	\
>>> +				 SNDRV_PCM_FMTBIT_S24_3BE |	\
>>> +				 SNDRV_PCM_FMTBIT_S24_LE |	\
>>> +				 SNDRV_PCM_FMTBIT_S24_BE |	\
>>> +				 SNDRV_PCM_FMTBIT_S32_LE |	\
>>> +				 SNDRV_PCM_FMTBIT_S32_BE	\
>>> +				 )
>>> +
>>> +static int mchp_spdiftx_info(struct snd_kcontrol *kcontrol,
>>> +			     struct snd_ctl_elem_info *uinfo)
>>> +{
>>> +	uinfo->type = SNDRV_CTL_ELEM_TYPE_IEC958;
>>> +	uinfo->count = 1;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int mchp_spdiftx_cs_get(struct snd_kcontrol *kcontrol,
>>> +			       struct snd_ctl_elem_value *uvalue)
>>> +{
>>> +	unsigned long flags;
>>> +	struct snd_soc_dai *dai = snd_kcontrol_chip(kcontrol);
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +
>>> +	spin_lock_irqsave(&ctrl->lock, flags);
>>> +	memcpy(uvalue->value.iec958.status, ctrl->ch_stat,
>>> +	       sizeof(ctrl->ch_stat));
>>> +	spin_unlock_irqrestore(&ctrl->lock, flags);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int mchp_spdiftx_cs_put(struct snd_kcontrol *kcontrol,
>>> +			       struct snd_ctl_elem_value *uvalue)
>>> +{
>>> +	unsigned long flags;
>>> +	struct snd_soc_dai *dai = snd_kcontrol_chip(kcontrol);
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	int changed = 0;
>>> +	int i;
>>> +
>>> +	spin_lock_irqsave(&ctrl->lock, flags);
>>> +	for (i = 0; i < ARRAY_SIZE(ctrl->ch_stat); i++) {
>>> +		if (ctrl->ch_stat[i] != uvalue->value.iec958.status[i])
>>> +			changed = 1;
>>> +		ctrl->ch_stat[i] = uvalue->value.iec958.status[i];
>>> +	}
>>> +
>>> +	if (changed) {
>>> +		/* don't enable IP while we copy the channel status */
>>> +		if (mchp_spdiftx_is_running(dev)) {
>>> +			/*
>>> +			 * if SPDIF is running, wait for interrupt to write
>>> +			 * channel status
>>> +			 */
>>> +			regmap_write(dev->regmap, SPDIFTX_IER,
>>> +				     SPDIFTX_IR_CSRDY);
>>> +		} else {
>>> +			mchp_spdiftx_channel_status_write(dev);
>>> +		}
>>> +	}
>>> +	spin_unlock_irqrestore(&ctrl->lock, flags);
>>> +
>>> +	return changed;
>>> +}
>>> +
>>> +static int mchp_spdiftx_cs_mask(struct snd_kcontrol *kcontrol,
>>> +				struct snd_ctl_elem_value *uvalue)
>>> +{
>>> +	memset(uvalue->value.iec958.status, 0xff,
>>> +	       sizeof(uvalue->value.iec958.status));
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int mchp_spdiftx_subcode_get(struct snd_kcontrol *kcontrol,
>>> +				    struct snd_ctl_elem_value *uvalue)
>>> +{
>>> +	struct snd_soc_dai *dai = snd_kcontrol_chip(kcontrol);
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	unsigned long flags;
>>> +
>>> +	spin_lock_irqsave(&ctrl->lock, flags);
>>> +	memcpy(uvalue->value.iec958.subcode, ctrl->user_data,
>>> +	       sizeof(ctrl->user_data));
>>> +	spin_unlock_irqrestore(&ctrl->lock, flags);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int mchp_spdiftx_subcode_put(struct snd_kcontrol *kcontrol,
>>> +				    struct snd_ctl_elem_value *uvalue)
>>> +{
>>> +	unsigned long flags;
>>> +	struct snd_soc_dai *dai = snd_kcontrol_chip(kcontrol);
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +	struct mchp_spdiftx_mixer_control *ctrl = &dev->control;
>>> +	int changed = 0;
>>> +	int i;
>>> +
>>> +	spin_lock_irqsave(&ctrl->lock, flags);
>>> +	for (i = 0; i < ARRAY_SIZE(ctrl->user_data); i++) {
>>> +		if (ctrl->user_data[i] != uvalue->value.iec958.subcode[i])
>>> +			changed = 1;
>>> +
>>> +		ctrl->user_data[i] = uvalue->value.iec958.subcode[i];
>>> +	}
>>> +	if (changed) {
>>> +		if (mchp_spdiftx_is_running(dev)) {
>>> +			/*
>>> +			 * if SPDIF is running, wait for interrupt to write
>>> +			 * user data
>>> +			 */
>>> +			regmap_write(dev->regmap, SPDIFTX_IER,
>>> +				     SPDIFTX_IR_UDRDY);
>>> +		} else {
>>> +			mchp_spdiftx_user_data_write(dev);
>>> +		}
>>> +	}
>>> +	spin_unlock_irqrestore(&ctrl->lock, flags);
>>> +
>>> +	return changed;
>>> +}
>>> +
>>> +static struct snd_kcontrol_new mchp_spdiftx_ctrls[] = {
>>> +	/* Channel status controller */
>>> +	{
>>> +		.iface = SNDRV_CTL_ELEM_IFACE_PCM,
>>> +		.name = SNDRV_CTL_NAME_IEC958("", PLAYBACK, DEFAULT),
>>> +		.access = SNDRV_CTL_ELEM_ACCESS_READWRITE |
>>> +			SNDRV_CTL_ELEM_ACCESS_VOLATILE,
>>> +		.info = mchp_spdiftx_info,
>>> +		.get = mchp_spdiftx_cs_get,
>>> +		.put = mchp_spdiftx_cs_put,
>>> +	},
>>> +	{
>>> +		.iface = SNDRV_CTL_ELEM_IFACE_PCM,
>>> +		.name = SNDRV_CTL_NAME_IEC958("", PLAYBACK, MASK),
>>> +		.access = SNDRV_CTL_ELEM_ACCESS_READ,
>>> +			SNDRV_CTL_ELEM_ACCESS_VOLATILE,
>>> +		.info = mchp_spdiftx_info,
>>> +		.get = mchp_spdiftx_cs_mask,
>>> +	},
>>> +	/* User bits controller */
>>> +	{
>>> +		.iface = SNDRV_CTL_ELEM_IFACE_PCM,
>>> +		.name = "IEC958 Subcode Playback Default",
>>> +		.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
>>> +		.info = mchp_spdiftx_info,
>>> +		.get = mchp_spdiftx_subcode_get,
>>> +		.put = mchp_spdiftx_subcode_put,
>>> +	},
>>> +};
>>> +
>>> +static int mchp_spdiftx_dai_probe(struct snd_soc_dai *dai)
>>> +{
>>> +	struct mchp_spdiftx_dev *dev = snd_soc_dai_get_drvdata(dai);
>>> +
>>> +	snd_soc_dai_init_dma_data(dai, &dev->playback, NULL);
>>> +
>>> +	/* Add controls */
>>> +	snd_soc_add_dai_controls(dai, mchp_spdiftx_ctrls,
>>> +				 ARRAY_SIZE(mchp_spdiftx_ctrls));
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static struct snd_soc_dai_driver mchp_spdiftx_dai = {
>>> +	.name = "mchp-spdiftx",
>>> +	.probe	= mchp_spdiftx_dai_probe,
>>> +	.playback = {
>>> +		.stream_name = "S/PDIF TX Playback",
>>> +		.channels_min = 1,
>>> +		.channels_max = 2,
>>> +		.rates = MCHP_SPDIFTX_RATES,
>>> +		.formats = MCHP_SPDIFTX_FORMATS,
>>> +	},
>>> +	.ops = &mchp_spdiftx_dai_ops,
>>> +};
>>> +
>>> +static const struct snd_soc_component_driver mchp_spdiftx_component = {
>>> +	.name		= "mchp-spdiftx",
>>> +};
>>> +
>>> +static const struct of_device_id mchp_spdiftx_dt_ids[] = {
>>> +	{
>>> +		.compatible = "microchip,sama7g5-spdiftx",
>>> +	},
>>> +	{ /* sentinel */ }
>>> +};
>>> +
>>> +MODULE_DEVICE_TABLE(of, mchp_spdiftx_dt_ids);
>>> +static int mchp_spdiftx_probe(struct platform_device *pdev)
>>> +{
>>> +	struct device_node *np = pdev->dev.of_node;
>>> +	const struct of_device_id *match;
>>> +	struct mchp_spdiftx_dev *dev;
>>> +	struct resource *mem;
>>> +	struct regmap *regmap;
>>> +	void __iomem *base;
>>> +	struct mchp_spdiftx_mixer_control *ctrl;
>>> +	int irq;
>>> +	int err;
>>> +
>>> +	/* Get memory for driver data. */
>>> +	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
>>> +	if (!dev)
>>> +		return -ENOMEM;
>>> +
>>> +	/* Get hardware capabilities. */
>>> +	match = of_match_node(mchp_spdiftx_dt_ids, np);
>>> +	if (match)
>>> +		dev->caps = match->data;
>>> +
>>> +	/* Map I/O registers. */
>>> +	base = devm_platform_get_and_ioremap_resource(pdev, 0, &mem);
>>> +	if (IS_ERR(base))
>>> +		return PTR_ERR(base);
>>> +
>>> +	regmap = devm_regmap_init_mmio(&pdev->dev, base,
>>> +				       &mchp_spdiftx_regmap_config);
>>> +	if (IS_ERR(regmap))
>>> +		return PTR_ERR(regmap);
>>> +
>>> +	/* Request IRQ */
>>> +	irq = platform_get_irq(pdev, 0);
>>> +	if (irq < 0)
>>> +		return irq;
>>> +
>>> +	err = devm_request_irq(&pdev->dev, irq, mchp_spdiftx_interrupt, 0,
>>> +			       dev_name(&pdev->dev), dev);
>>> +	if (err)
>>> +		return err;
>>> +
>>> +	/* Get the peripheral clock */
>>> +	dev->pclk = devm_clk_get(&pdev->dev, "pclk");
>>> +	if (IS_ERR(dev->pclk)) {
>>> +		err = PTR_ERR(dev->pclk);
>>> +		dev_err(&pdev->dev,
>>> +			"failed to get the peripheral clock: %d\n", err);
>>> +		return err;
>>> +	}
>>> +
>>> +	/* Get the generic clock */
>>> +	dev->gclk = devm_clk_get(&pdev->dev, "gclk");
>>> +	if (IS_ERR(dev->gclk)) {
>>> +		err = PTR_ERR(dev->gclk);
>>> +		dev_err(&pdev->dev,
>>> +			"failed to get the PMC generic clock: %d\n", err);
>>> +		return err;
>>> +	}
>>> +
>>> +	ctrl = &dev->control;
>>> +	spin_lock_init(&ctrl->lock);
>>> +
>>> +	/* Init channel status */
>>> +	ctrl->ch_stat[0] = IEC958_AES0_CON_NOT_COPYRIGHT |
>>> +			   IEC958_AES0_CON_EMPHASIS_NONE;
>>> +
>>> +	dev->dev = &pdev->dev;
>>> +	dev->regmap = regmap;
>>> +	platform_set_drvdata(pdev, dev);
>>> +
>>> +	dev->playback.addr = (dma_addr_t)mem->start + SPDIFTX_CDR;
>>> +	dev->playback.addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
>>> +
>>> +	err = devm_snd_dmaengine_pcm_register(&pdev->dev, NULL, 0);
>>> +	if (err) {
>>> +		dev_err(&pdev->dev, "failed to register PMC: %d\n", err);
>>> +		return err;
>>> +	}
>>> +
>>> +	err = devm_snd_soc_register_component(&pdev->dev,
>>> +					      &mchp_spdiftx_component,
>>> +					      &mchp_spdiftx_dai, 1);
>>> +	if (err) {
>>> +		dev_err(&pdev->dev, "failed to register component: %d\n", err);
>>> +		return err;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static struct platform_driver mchp_spdiftx_driver = {
>>> +	.probe	= mchp_spdiftx_probe,
>>> +	.driver	= {
>>> +		.name	= "mchp_spdiftx",
>>> +		.of_match_table = of_match_ptr(mchp_spdiftx_dt_ids),
>>> +	},
>>> +};
>>> +
>>> +module_platform_driver(mchp_spdiftx_driver);
>>> +
>>> +MODULE_AUTHOR("Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>");
>>> +MODULE_DESCRIPTION("Microchip S/PDIF TX Controller Driver");
>>> +MODULE_LICENSE("GPL v2");
> 




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