Re: [PATCH 2/4] drivers: iio: ti_am335x_adc: add dma support

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On Wednesday 21 September 2016 09:41 PM, Mugunthan V N wrote:
> This patch adds the required pieces to ti_am335x_adc driver for
> DMA support
> 
> Signed-off-by: Mugunthan V N <mugunthanvnm@xxxxxx>
> ---
>  drivers/iio/adc/ti_am335x_adc.c      | 160 ++++++++++++++++++++++++++++++++++-
>  include/linux/mfd/ti_am335x_tscadc.h |   7 ++
>  2 files changed, 164 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> index c3cfacca..89d0b07 100644
> --- a/drivers/iio/adc/ti_am335x_adc.c
> +++ b/drivers/iio/adc/ti_am335x_adc.c
> @@ -30,10 +30,32 @@
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/kfifo_buf.h>
>  
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> +
> +#define DMA_BUFFER_SIZE		SZ_2K
> +
> +struct tiadc_dma {
> +	/* Filter function */
> +	dma_filter_fn		fn;
> +	/* Parameter to the filter function */
> +	void			*param;

These will not be needed with newer APIs (see below)

> +	struct dma_slave_config	conf;
> +	struct dma_chan		*chan;
> +	dma_addr_t		addr;
> +	dma_cookie_t		cookie;
> +	u8			*buf;
> +	bool			valid_buf_seg;
> +	int			buf_offset;
> +	u8			fifo_thresh;
> +};
> +
>  struct tiadc_device {
>  	struct ti_tscadc_dev *mfd_tscadc;
> +	struct tiadc_dma dma;
>  	struct mutex fifo1_lock; /* to protect fifo access */
>  	int channels;
> +	int total_ch_enabled;
>  	u8 channel_line[8];
>  	u8 channel_step[8];
>  	int buffer_en_ch_steps;
> @@ -184,6 +206,7 @@ static irqreturn_t tiadc_worker_h(int irq, void *private)
>  	u16 *data = adc_dev->data;
>  
>  	fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
> +
>  	for (k = 0; k < fifo1count; k = k + i) {
>  		for (i = 0; i < (indio_dev->scan_bytes)/2; i++) {
>  			read = tiadc_readl(adc_dev, REG_FIFO1);
> @@ -198,6 +221,68 @@ static irqreturn_t tiadc_worker_h(int irq, void *private)
>  	return IRQ_HANDLED;
>  }
>  
> +static void tiadc_dma_rx_complete(void *param)
> +{
> +	struct iio_dev *indio_dev = param;
> +	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> +	struct tiadc_dma *dma = &adc_dev->dma;
> +	u8 *data;
> +	int i;
> +
> +	data = dma->valid_buf_seg ? dma->buf + dma->buf_offset : dma->buf;
> +	dma->valid_buf_seg = !dma->valid_buf_seg;
> +
> +	for (i = 0; i < dma->buf_offset; i += indio_dev->scan_bytes) {
> +		iio_push_to_buffers(indio_dev, data);
> +		data += indio_dev->scan_bytes;
> +	}
> +}
> +
> +static int tiadc_start_dma(struct iio_dev *indio_dev)
> +{
> +	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> +	struct tiadc_dma *dma = &adc_dev->dma;
> +	struct dma_async_tx_descriptor *desc;
> +
> +	dma->valid_buf_seg = false;
> +	dma->fifo_thresh = FIFO1_THRESHOLD;
> +	/*
> +	 * Make the fifo thresh as the multiple of total number of
> +	 * channels enabled, so make sure that that cyclic DMA period
> +	 * length is also a multiple of total number of channels
> +	 * enabled. This ensures that no invalid data is reported
> +	 * to the stack via iio_push_to_buffers().
> +	 */
> +	dma->fifo_thresh -= (dma->fifo_thresh + 1) % adc_dev->total_ch_enabled;

Can we use rounddown(FIFO1_THRESHOLD + 1, adc_dev->total_ch_enabled)?

> +	dma->buf_offset = DMA_BUFFER_SIZE / 2;
> +	/* Make sure that period length is multiple of fifo thresh level */
> +	dma->buf_offset -= dma->buf_offset % ((dma->fifo_thresh + 1) *
> +					      sizeof(u16));
> +

Can we use rounddown()?

> +	dma->conf.src_maxburst = dma->fifo_thresh + 1;
> +	dmaengine_slave_config(dma->chan, &dma->conf);
> +
> +	desc = dmaengine_prep_dma_cyclic(dma->chan, dma->addr,
> +					 dma->buf_offset * 2,
> +					 dma->buf_offset, DMA_DEV_TO_MEM,
> +					 DMA_PREP_INTERRUPT);
> +	if (!desc)
> +		return -EBUSY;
> +
> +	desc->callback = tiadc_dma_rx_complete;
> +	desc->callback_param = indio_dev;
> +
> +	dma->cookie = dmaengine_submit(desc);
> +
> +	dma_async_issue_pending(dma->chan);
> +
> +	tiadc_writel(adc_dev, REG_FIFO1THR, dma->fifo_thresh);
> +	tiadc_writel(adc_dev, REG_DMA1REQ, dma->fifo_thresh);
> +	tiadc_writel(adc_dev, REG_DMAENABLE_SET, DMA_FIFO1);
> +
> +	return 0;
> +}
> +
>  static int tiadc_buffer_preenable(struct iio_dev *indio_dev)
>  {
>  	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> @@ -218,20 +303,30 @@ static int tiadc_buffer_preenable(struct iio_dev *indio_dev)
>  static int tiadc_buffer_postenable(struct iio_dev *indio_dev)
>  {
>  	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> +	struct tiadc_dma *dma = &adc_dev->dma;
>  	unsigned int enb = 0;
>  	u8 bit;
> +	u32 irq_enable;
>  
>  	tiadc_step_config(indio_dev);
> -	for_each_set_bit(bit, indio_dev->active_scan_mask, adc_dev->channels)
> +	for_each_set_bit(bit, indio_dev->active_scan_mask, adc_dev->channels) {
>  		enb |= (get_adc_step_bit(adc_dev, bit) << 1);
> +		adc_dev->total_ch_enabled++;
> +	}
>  	adc_dev->buffer_en_ch_steps = enb;
>  
> +	if (dma->chan)
> +		tiadc_start_dma(indio_dev);
> +
>  	am335x_tsc_se_set_cache(adc_dev->mfd_tscadc, enb);
>  
>  	tiadc_writel(adc_dev,  REG_IRQSTATUS, IRQENB_FIFO1THRES
>  				| IRQENB_FIFO1OVRRUN | IRQENB_FIFO1UNDRFLW);
> -	tiadc_writel(adc_dev,  REG_IRQENABLE, IRQENB_FIFO1THRES
> -				| IRQENB_FIFO1OVRRUN);
> +
> +	irq_enable = IRQENB_FIFO1OVRRUN;
> +	if (!dma->chan)
> +		irq_enable |= IRQENB_FIFO1THRES;
> +	tiadc_writel(adc_dev,  REG_IRQENABLE, irq_enable);
>  
>  	return 0;
>  }
> @@ -239,12 +334,18 @@ static int tiadc_buffer_postenable(struct iio_dev *indio_dev)
>  static int tiadc_buffer_predisable(struct iio_dev *indio_dev)
>  {
>  	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> +	struct tiadc_dma *dma = &adc_dev->dma;
>  	int fifo1count, i, read;
>  
>  	tiadc_writel(adc_dev, REG_IRQCLR, (IRQENB_FIFO1THRES |
>  				IRQENB_FIFO1OVRRUN | IRQENB_FIFO1UNDRFLW));
>  	am335x_tsc_se_clr(adc_dev->mfd_tscadc, adc_dev->buffer_en_ch_steps);
>  	adc_dev->buffer_en_ch_steps = 0;
> +	adc_dev->total_ch_enabled = 0;
> +	if (dma->chan) {
> +		tiadc_writel(adc_dev, REG_DMAENABLE_CLEAR, 0x2);
> +		dmaengine_terminate_async(dma->chan);
> +	}
>  
>  	/* Flush FIFO of leftover data in the time it takes to disable adc */
>  	fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
> @@ -430,6 +531,50 @@ static const struct iio_info tiadc_info = {
>  	.driver_module = THIS_MODULE,
>  };
>  
> +static bool the_no_dma_filter_fn(struct dma_chan *chan, void *param)
> +{
> +	return false;
> +}
> +
> +static int tiadc_request_dma(struct platform_device *pdev,
> +			     struct tiadc_device *adc_dev)
> +{
> +	struct tiadc_dma	*dma = &adc_dev->dma;
> +	dma_cap_mask_t		mask;
> +
> +	dma->fn = the_no_dma_filter_fn;
> +
> +	/* Default slave configuration parameters */
> +	dma->conf.direction = DMA_DEV_TO_MEM;
> +	dma->conf.src_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTES;
> +	dma->conf.src_addr = adc_dev->mfd_tscadc->tscadc_phys_base + REG_FIFO1;
> +
> +	dma_cap_zero(mask);
> +	dma_cap_set(DMA_CYCLIC, mask);
> +
> +	/* Get a channel for RX */
> +	dma->chan = dma_request_slave_channel_compat(mask,
> +						     dma->fn, dma->param,
> +						     adc_dev->mfd_tscadc->dev,
> +						     "fifo1");

Please use dma_request_chan() API instead, this does not need
dma_filter_fn and probe defer can be handled.

> +	if (!dma->chan)
> +		return -ENODEV;
> +
> +	/* RX buffer */
> +	dma->buf = dma_alloc_coherent(dma->chan->device->dev, DMA_BUFFER_SIZE,
> +				      &dma->addr, GFP_KERNEL);
> +	if (!dma->buf)
> +		goto err;
> +
> +	dev_dbg_ratelimited(adc_dev->mfd_tscadc->dev, "got dma channel\n");

Do we need _ratelimited? AFAICS, this print is called only once.

> +
> +	return 0;
> +err:
> +	dma_release_channel(dma->chan);
> +
> +	return -ENOMEM;
> +}
> +
>  static int tiadc_parse_dt(struct platform_device *pdev,
>  			  struct tiadc_device *adc_dev)
>  {
> @@ -512,8 +657,14 @@ static int tiadc_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, indio_dev);
>  
> +	err = tiadc_request_dma(pdev, adc_dev);
> +	if (err && err != -ENODEV)
> +		goto err_dma;
> +
>  	return 0;
>  
> +err_dma:
> +	iio_device_unregister(indio_dev);
>  err_buffer_unregister:
>  	tiadc_iio_buffered_hardware_remove(indio_dev);
>  err_free_channels:
> @@ -525,8 +676,11 @@ static int tiadc_remove(struct platform_device *pdev)
>  {
>  	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>  	struct tiadc_device *adc_dev = iio_priv(indio_dev);
> +	struct tiadc_dma *dma = &adc_dev->dma;
>  	u32 step_en;
>  
> +	if (dma->chan)
> +		dma_release_channel(dma->chan);

dma_free_coherent() for dma->buf?

>  	iio_device_unregister(indio_dev);
>  	tiadc_iio_buffered_hardware_remove(indio_dev);
>  	tiadc_channels_remove(indio_dev);
> diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h
> index e45a208..fb9dc99 100644
> --- a/include/linux/mfd/ti_am335x_tscadc.h
> +++ b/include/linux/mfd/ti_am335x_tscadc.h
> @@ -23,6 +23,8 @@
>  #define REG_IRQENABLE		0x02C
>  #define REG_IRQCLR		0x030
>  #define REG_IRQWAKEUP		0x034
> +#define REG_DMAENABLE_SET	0x038
> +#define REG_DMAENABLE_CLEAR	0x038
>  #define REG_CTRL		0x040
>  #define REG_ADCFSM		0x044
>  #define REG_CLKDIV		0x04C
> @@ -36,6 +38,7 @@
>  #define REG_FIFO0THR		0xE8
>  #define REG_FIFO1CNT		0xF0
>  #define REG_FIFO1THR		0xF4
> +#define REG_DMA1REQ		0xF8
>  #define REG_FIFO0		0x100
>  #define REG_FIFO1		0x200
>  
> @@ -126,6 +129,10 @@
>  #define FIFOREAD_DATA_MASK (0xfff << 0)
>  #define FIFOREAD_CHNLID_MASK (0xf << 16)
>  
> +/* DMA ENABLE/CLEAR Register */
> +#define DMA_FIFO0		BIT(0)
> +#define DMA_FIFO1		BIT(1)
> +
>  /* Sequencer Status */
>  #define SEQ_STATUS BIT(5)
>  #define CHARGE_STEP		0x11
> 

-- 
Regards
Vignesh
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