Re: [PATCH v3 2/4] drivers: iio: ti_am335x_adc: add dma support

From: Jonathan Cameron
Date: Sat Oct 22 2016 - 13:47:50 EST

On 19/10/16 09:52, Mugunthan V N wrote:
> On Sunday 09 October 2016 02:00 PM, Jonathan Cameron wrote:
>> 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@xxxxxx>
>> 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.
Question answered below. So just need that Ack from Lee.


>>
>> 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?
>
> In non DMA case, dms->chan will be NULL and IRQENB_FIFO1THRES interrupt
> will be enabled to pop the ADC samples.
>
oops. Thanks for pointing out how I'd misread this!
So just after the ack from Lee now.
Jonathan
> Regards
> Mugunthan V N
>
>>> + 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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