[PATCH 2/4] drivers: iio: ti_am335x_adc: add dma support
Mugunthan V N
mugunthanvnm at ti.com
Thu Sep 22 03:56:15 PDT 2016
On Thursday 22 September 2016 12:50 PM, Peter Ujfalusi wrote:
> On 09/21/16 19:11, 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 at ti.com>
>> ---
>> 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;
>> + 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;
>
> bool valid_buf_seg ? The buffer segment is valid or not valid? Which buffer
> segment is valid when valid_buf_seg is true?
>
> I know what this is doing, but it is logically not correct.
>
> Instead you could have:
>
> int current_period; /* The period the DMA is working on */
>
> When you start the DMA:
> dma->current_period = 0; /* We start to fill period 0 */
>
> In here:
>
> u8 *data = dma->buf + (dma->current_period * dma_period_size);
>
>> + dma->valid_buf_seg = !dma->valid_buf_seg;
>
> /* Currently we have only two periods, so we can just */
> dma->current_period = !dma->current_period;
> /* or */
> dma->current_period = 1 - dma->current_period; /* swap the buffer ID */
>
> I think this would make it better to follow and if later you figure that you
> want three or more periods instead of the two, it is going to be easier to add
> that.
Okay, will change this in next version patch.
>
>> +
>> + 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;
>
> FIFO1_THRESHOLD is defined as 19 in the global header file, so
> if you have 2 channels enabled the trigger comes when the FIFO have 10
> samples/ch, in case of all 8 channels enabled you will round it down the
> trigger comes when you have 2 samples/ch.
>
> Would not be better to try to use high threshold for the FIFO to reduce the
> number of DMA requests needed runtime?
>
> It is OK as it is at the moment, but I think it would make sense to try to
> maximize the FIFO usage.
I had already tried with higher values, It works fine. Just don't want
to change the non-DMA implementation as I am not aware of any
limitations why at the first place they have used fifo threshold as 19.
>
>> + /*
>> + * 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;
>> + 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));
>> +
>> + 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,
>
> I find the buf_offset name and it's use really confusing. It should be called
> period_size, really.
Yes, will fix this.
>
>> + 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");
>
> dma_request_chan()
Will fix this.
>
>> + 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");
>> +
>> + 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);
>> 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
Mugunthan V N
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