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Date:   Sun, 9 Oct 2016 09:30:39 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Mugunthan V N <mugunthanvnm@...com>, linux-iio@...r.kernel.org
Cc:     Tony Lindgren <tony@...mide.com>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Lee Jones <lee.jones@...aro.org>, Vignesh R <vigneshr@...com>,
        "Andrew F . Davis" <afd@...com>, linux-omap@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Sekhar Nori <nsekhar@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        John Syne <john3909@...il.com>
Subject: Re: [PATCH v3 2/4] drivers: iio: ti_am335x_adc: add dma support

On 05/10/16 10:04, 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@...com>
Hi,

Just the one question inline.  I'll also need an Ack from Lee as
this touches code in mfd (as does the previous patch).
We have obviously missed this merge window, so no particular rush.

Otherwise, looking very nice indeed.  Got to get my BBB out and play
with this now ;)

Jonathan
> ---
>  drivers/iio/adc/ti_am335x_adc.c      | 148 ++++++++++++++++++++++++++++++++++-
>  include/linux/mfd/ti_am335x_tscadc.h |   7 ++
>  2 files changed, 152 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> index c3cfacca..ad9dec3 100644
> --- a/drivers/iio/adc/ti_am335x_adc.c
> +++ b/drivers/iio/adc/ti_am335x_adc.c
> @@ -30,10 +30,28 @@
>  #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 {
> +	struct dma_slave_config	conf;
> +	struct dma_chan		*chan;
> +	dma_addr_t		addr;
> +	dma_cookie_t		cookie;
> +	u8			*buf;
> +	int			current_period;
> +	int			period_size;
> +	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;
> @@ -198,6 +216,67 @@ 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->buf + dma->current_period * dma->period_size;
> +	dma->current_period = 1 - dma->current_period; /* swap the buffer ID */
> +
> +	for (i = 0; i < dma->period_size; i += indio_dev->scan_bytes) {
> +		iio_push_to_buffers(indio_dev, data);
> +		data += indio_dev->scan_bytes;
> +	}
Hmm. Another case for the mooted iio_push_to_buffers_multi. Guess
we should move on with that one ;)
> +}
> +
> +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->current_period = 0; /* We start to fill period 0 */
> +	/*
> +	 * Make the fifo thresh as the multiple of total number of
> +	 * channels enabled, so make sure 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 = rounddown(FIFO1_THRESHOLD + 1,
> +				     adc_dev->total_ch_enabled) - 1;
> +	/* Make sure that period length is multiple of fifo thresh level */
> +	dma->period_size = rounddown(DMA_BUFFER_SIZE / 2,
> +				    (dma->fifo_thresh + 1) * sizeof(u16));
> +
> +	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->period_size * 2,
> +					 dma->period_size, 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 +297,30 @@ 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 irq_enable;
>  	unsigned int enb = 0;
>  	u8 bit;
>  
>  	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;
This changes the non dma behaviour as we no longer set IRQENB_FIFO1THRES.
Why?  Was it wrong before?
> +	tiadc_writel(adc_dev,  REG_IRQENABLE, irq_enable);
>  
>  	return 0;
>  }
> @@ -239,12 +328,18 @@ 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 +525,41 @@ static const struct iio_info tiadc_info = {
>  	.driver_module = THIS_MODULE,
>  };
>  
> +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;
> +
> +	/* 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_chan(adc_dev->mfd_tscadc->dev, "fifo1");
> +	if (IS_ERR(dma->chan)) {
> +		int ret = PTR_ERR(dma->chan);
> +
> +		dma->chan = NULL;
> +		return ret;
> +	}
> +
> +	/* RX buffer */
> +	dma->buf = dma_alloc_coherent(dma->chan->device->dev, DMA_BUFFER_SIZE,
> +				      &dma->addr, GFP_KERNEL);
> +	if (!dma->buf)
> +		goto err;
> +
> +	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 +642,14 @@ static int tiadc_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, indio_dev);
>  
> +	err = tiadc_request_dma(pdev, adc_dev);
> +	if (err && err == -EPROBE_DEFER)
> +		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 +661,14 @@ 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_free_coherent(dma->chan->device->dev, DMA_BUFFER_SIZE,
> +				  dma->buf, dma->addr);
> +		dma_release_channel(dma->chan);
> +	}
>  	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..b9a53e0 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	0x03c
>  #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
> 

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