drivers: iio: ti_am335x_adc: add dma support

This patch adds the required pieces to ti_am335x_adc driver for
DMA support

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
index c3cfacc..ad9dec3 100644 (file)
--- 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;
+       }
+}
+
+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;
+       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 (file)
--- 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