iio: ti_am335x_adc: Add continuous sampling support

Previously the driver had only one-shot reading functionality.
This patch adds continuous sampling support to the driver.

Continuous sampling starts when buffer is enabled.
HW IRQ wakes worker thread that pushes samples to userspace.
Sampling stops when buffer is disabled by userspace.

Patil Rachna (TI) laid the ground work for ADC HW register access.
Russ Dill (TI) fixed bugs in the driver relevant to FIFOs and IRQs.

I fixed channel scanning so multiple ADC channels can be read
simultaneously and pushed to userspace.
Restructured the driver to fit IIO ABI.
And added INDIO_BUFFER_HARDWARE mode.

Signed-off-by: Zubair Lutfullah <zubair.lutfullah@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Russ Dill <Russ.Dill@ti.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

2 files changed, 209 insertions, 5 deletions

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 0cf5c611b4c6..8b885188b839 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -177,6 +177,7 @@ config TI_ADC081C
 config TI_AM335X_ADC
         tristate "TI's AM335X ADC driver"
         depends on MFD_TI_AM335X_TSCADC
+        select IIO_KFIFO_BUF
         help
           Say yes here to build support for Texas Instruments ADC
           driver which is also a MFD client.
diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
index ebe93eba3ec8..5287bffd8a75 100644
--- a/drivers/iio/adc/ti_am335x_adc.c
+++ b/drivers/iio/adc/ti_am335x_adc.c
@@ -28,12 +28,20 @@
 #include <linux/iio/driver.h>
 
 #include <linux/mfd/ti_am335x_tscadc.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/kfifo_buf.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
 
 struct tiadc_device {
         struct ti_tscadc_dev *mfd_tscadc;
         int channels;
         u8 channel_line[8];
         u8 channel_step[8];
+        int buffer_en_ch_steps;
+        struct iio_trigger *trig;
+        u16 data[8];
 };
 
 static unsigned int tiadc_readl(struct tiadc_device *adc, unsigned int reg)
@@ -56,8 +64,14 @@ static u32 get_adc_step_mask(struct tiadc_device *adc_dev)
         return step_en;
 }
 
-static void tiadc_step_config(struct tiadc_device *adc_dev)
+static u32 get_adc_step_bit(struct tiadc_device *adc_dev, int chan)
 {
+        return 1 << adc_dev->channel_step[chan];
+}
+
+static void tiadc_step_config(struct iio_dev *indio_dev)
+{
+        struct tiadc_device *adc_dev = iio_priv(indio_dev);
         unsigned int stepconfig;
         int i, steps;
 
@@ -72,7 +86,11 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
          */
 
         steps = TOTAL_STEPS - adc_dev->channels;
-        stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1;
+        if (iio_buffer_enabled(indio_dev))
+                stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1
+                                        | STEPCONFIG_MODE_SWCNT;
+        else
+                stepconfig = STEPCONFIG_AVG_16 | STEPCONFIG_FIFO1;
 
         for (i = 0; i < adc_dev->channels; i++) {
                 int chan;
@@ -85,9 +103,175 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
                 adc_dev->channel_step[i] = steps;
                 steps++;
         }
+}
+
+static irqreturn_t tiadc_irq_h(int irq, void *private)
+{
+        struct iio_dev *indio_dev = private;
+        struct tiadc_device *adc_dev = iio_priv(indio_dev);
+        unsigned int status, config;
+        status = tiadc_readl(adc_dev, REG_IRQSTATUS);
+
+        /*
+         * ADC and touchscreen share the IRQ line.
+         * FIFO0 interrupts are used by TSC. Handle FIFO1 IRQs here only
+         */
+        if (status & IRQENB_FIFO1OVRRUN) {
+                /* FIFO Overrun. Clear flag. Disable/Enable ADC to recover */
+                config = tiadc_readl(adc_dev, REG_CTRL);
+                config &= ~(CNTRLREG_TSCSSENB);
+                tiadc_writel(adc_dev, REG_CTRL, config);
+                tiadc_writel(adc_dev, REG_IRQSTATUS, IRQENB_FIFO1OVRRUN
+                                | IRQENB_FIFO1UNDRFLW | IRQENB_FIFO1THRES);
+                tiadc_writel(adc_dev, REG_CTRL, (config | CNTRLREG_TSCSSENB));
+                return IRQ_HANDLED;
+        } else if (status & IRQENB_FIFO1THRES) {
+                /* Disable irq and wake worker thread */
+                tiadc_writel(adc_dev, REG_IRQCLR, IRQENB_FIFO1THRES);
+                return IRQ_WAKE_THREAD;
+        }
+
+        return IRQ_NONE;
+}
+
+static irqreturn_t tiadc_worker_h(int irq, void *private)
+{
+        struct iio_dev *indio_dev = private;
+        struct tiadc_device *adc_dev = iio_priv(indio_dev);
+        int i, k, fifo1count, read;
+        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);
+                        data[i] = read & FIFOREAD_DATA_MASK;
+                }
+                iio_push_to_buffers(indio_dev, (u8 *) data);
+        }
+
+        tiadc_writel(adc_dev, REG_IRQSTATUS, IRQENB_FIFO1THRES);
+        tiadc_writel(adc_dev, REG_IRQENABLE, IRQENB_FIFO1THRES);
+
+        return IRQ_HANDLED;
+}
+
+static int tiadc_buffer_preenable(struct iio_dev *indio_dev)
+{
+        struct tiadc_device *adc_dev = iio_priv(indio_dev);
+        int i, fifo1count, read;
+
+        tiadc_writel(adc_dev, REG_IRQCLR, (IRQENB_FIFO1THRES |
+                                IRQENB_FIFO1OVRRUN |
+                                IRQENB_FIFO1UNDRFLW));
+
+        /* Flush FIFO. Needed in corner cases in simultaneous tsc/adc use */
+        fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
+        for (i = 0; i < fifo1count; i++)
+                read = tiadc_readl(adc_dev, REG_FIFO1);
+
+        return iio_sw_buffer_preenable(indio_dev);
+}
+
+static int tiadc_buffer_postenable(struct iio_dev *indio_dev)
+{
+        struct tiadc_device *adc_dev = iio_priv(indio_dev);
+        struct iio_buffer *buffer = indio_dev->buffer;
+        unsigned int enb = 0;
+        u8 bit;
+
+        tiadc_step_config(indio_dev);
+        for_each_set_bit(bit, buffer->scan_mask, adc_dev->channels)
+                enb |= (get_adc_step_bit(adc_dev, bit) << 1);
+        adc_dev->buffer_en_ch_steps = enb;
+
+        am335x_tsc_se_set(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);
+
+        return 0;
+}
+
+static int tiadc_buffer_predisable(struct iio_dev *indio_dev)
+{
+        struct tiadc_device *adc_dev = iio_priv(indio_dev);
+        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);
 
+        /* Flush FIFO of leftover data in the time it takes to disable adc */
+        fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
+        for (i = 0; i < fifo1count; i++)
+                read = tiadc_readl(adc_dev, REG_FIFO1);
+
+        return 0;
 }
 
+static int tiadc_buffer_postdisable(struct iio_dev *indio_dev)
+{
+        tiadc_step_config(indio_dev);
+
+        return 0;
+}
+
+static const struct iio_buffer_setup_ops tiadc_buffer_setup_ops = {
+        .preenable = &tiadc_buffer_preenable,
+        .postenable = &tiadc_buffer_postenable,
+        .predisable = &tiadc_buffer_predisable,
+        .postdisable = &tiadc_buffer_postdisable,
+};
+
+int tiadc_iio_buffered_hardware_setup(struct iio_dev *indio_dev,
+        irqreturn_t (*pollfunc_bh)(int irq, void *p),
+        irqreturn_t (*pollfunc_th)(int irq, void *p),
+        int irq,
+        unsigned long flags,
+        const struct iio_buffer_setup_ops *setup_ops)
+{
+        int ret;
+
+        indio_dev->buffer = iio_kfifo_allocate(indio_dev);
+        if (!indio_dev->buffer)
+                return -ENOMEM;
+
+        ret = request_threaded_irq(irq, pollfunc_th, pollfunc_bh,
+                                flags, indio_dev->name, indio_dev);
+        if (ret)
+                goto error_kfifo_free;
+
+        indio_dev->setup_ops = setup_ops;
+        indio_dev->modes |= INDIO_BUFFER_HARDWARE;
+
+        ret = iio_buffer_register(indio_dev,
+                                  indio_dev->channels,
+                                  indio_dev->num_channels);
+        if (ret)
+                goto error_free_irq;
+
+        return 0;
+
+error_free_irq:
+        free_irq(irq, indio_dev);
+error_kfifo_free:
+        iio_kfifo_free(indio_dev->buffer);
+        return ret;
+}
+
+static void tiadc_iio_buffered_hardware_remove(struct iio_dev *indio_dev)
+{
+        struct tiadc_device *adc_dev = iio_priv(indio_dev);
+
+        free_irq(adc_dev->mfd_tscadc->irq, indio_dev);
+        iio_kfifo_free(indio_dev->buffer);
+        iio_buffer_unregister(indio_dev);
+}
+
+
 static const char * const chan_name_ain[] = {
         "AIN0",
         "AIN1",
@@ -120,6 +304,7 @@ static int tiadc_channel_init(struct iio_dev *indio_dev, int channels)
                 chan->channel = adc_dev->channel_line[i];
                 chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
                 chan->datasheet_name = chan_name_ain[chan->channel];
+                chan->scan_index = i;
                 chan->scan_type.sign = 'u';
                 chan->scan_type.realbits = 12;
                 chan->scan_type.storagebits = 16;
@@ -147,6 +332,10 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
         u32 step_en;
         unsigned long timeout = jiffies + usecs_to_jiffies
                                 (IDLE_TIMEOUT * adc_dev->channels);
+
+        if (iio_buffer_enabled(indio_dev))
+                return -EBUSY;
+
         step_en = get_adc_step_mask(adc_dev);
         am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
 
@@ -237,20 +426,33 @@ static int tiadc_probe(struct platform_device *pdev)
         indio_dev->modes = INDIO_DIRECT_MODE;
         indio_dev->info = &tiadc_info;
 
-        tiadc_step_config(adc_dev);
+        tiadc_step_config(indio_dev);
+        tiadc_writel(adc_dev, REG_FIFO1THR, FIFO1_THRESHOLD);
 
         err = tiadc_channel_init(indio_dev, adc_dev->channels);
         if (err < 0)
                 return err;
 
-        err = iio_device_register(indio_dev);
+        err = tiadc_iio_buffered_hardware_setup(indio_dev,
+                &tiadc_worker_h,
+                &tiadc_irq_h,
+                adc_dev->mfd_tscadc->irq,
+                IRQF_SHARED,
+                &tiadc_buffer_setup_ops);
+
         if (err)
                 goto err_free_channels;
 
+        err = iio_device_register(indio_dev);
+        if (err)
+                goto err_buffer_unregister;
+
         platform_set_drvdata(pdev, indio_dev);
 
         return 0;
 
+err_buffer_unregister:
+        tiadc_iio_buffered_hardware_remove(indio_dev);
 err_free_channels:
         tiadc_channels_remove(indio_dev);
         return err;
@@ -263,6 +465,7 @@ static int tiadc_remove(struct platform_device *pdev)
         u32 step_en;
 
         iio_device_unregister(indio_dev);
+        tiadc_iio_buffered_hardware_remove(indio_dev);
         tiadc_channels_remove(indio_dev);
 
         step_en = get_adc_step_mask(adc_dev);
@@ -301,7 +504,7 @@ static int tiadc_resume(struct device *dev)
         restore &= ~(CNTRLREG_POWERDOWN);
         tiadc_writel(adc_dev, REG_CTRL, restore);
 
-        tiadc_step_config(adc_dev);
+        tiadc_step_config(indio_dev);
 
         return 0;
 }