staging:iio:ad7606: Avoid allocating buffer for each data capture

Currently the ad7606 driver dynamically allocates and frees a transfer
buffer each time a sample capture is performed in buffered mode, which
introduces unnecessary overhead. The driver state struct already contains a
buffer that is used for transfers in one-shot mode. This buffer is large
enough to hold all samples, but not the timestamp that might be present in
buffered mode. Extend the buffer size to be able to contain the timestamp
and update the buffered capture function to use this buffer.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/adc/ad7606.h b/drivers/staging/iio/adc/ad7606.h
index cf6be6500bfb3b88f0fd17a907dea3558daca463..129f94e57c238a472d95ed467064f73153cfd280 100644 (file)
--- a/drivers/staging/iio/adc/ad7606.h
+++ b/drivers/staging/iio/adc/ad7606.h
@@ -68,9 +68,9 @@ struct ad7606_state {
        /*
         * DMA (thus cache coherency maintenance) requires the
         * transfer buffers to live in their own cache lines.
+        * 8 * 16-bit samples + 64-bit timestamp
         */
-
-       unsigned short                  data[8] ____cacheline_aligned;
+       unsigned short                  data[12] ____cacheline_aligned;
 };
 
 struct ad7606_bus_ops {

diff --git a/drivers/staging/iio/adc/ad7606_ring.c b/drivers/staging/iio/adc/ad7606_ring.c
index 0572df9aad85278c9242f045fc5e766f01891ef8..7fa4ccccb72761ef72ccdbb257e68dfd99922967 100644 (file)
--- a/drivers/staging/iio/adc/ad7606_ring.c
+++ b/drivers/staging/iio/adc/ad7606_ring.c
@@ -46,15 +46,10 @@ static void ad7606_poll_bh_to_ring(struct work_struct *work_s)
        struct ad7606_state *st = container_of(work_s, struct ad7606_state,
                                                poll_work);
        struct iio_dev *indio_dev = iio_priv_to_dev(st);
-       __u8 *buf;
        int ret;
 
-       buf = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
-       if (!buf)
-               return;
-
        if (gpio_is_valid(st->pdata->gpio_frstdata)) {
-               ret = st->bops->read_block(st->dev, 1, buf);
+               ret = st->bops->read_block(st->dev, 1, st->data);
                if (ret)
                        goto done;
                if (!gpio_get_value(st->pdata->gpio_frstdata)) {
@@ -67,22 +62,21 @@ static void ad7606_poll_bh_to_ring(struct work_struct *work_s)
                        goto done;
                }
                ret = st->bops->read_block(st->dev,
-                       st->chip_info->num_channels - 1, buf + 2);
+                       st->chip_info->num_channels - 1, st->data + 1);
                if (ret)
                        goto done;
        } else {
                ret = st->bops->read_block(st->dev,
-                       st->chip_info->num_channels, buf);
+                       st->chip_info->num_channels, st->data);
                if (ret)
                        goto done;
        }
 
-       iio_push_to_buffers_with_timestamp(indio_dev, buf,
+       iio_push_to_buffers_with_timestamp(indio_dev, st->data,
                                           iio_get_time_ns(indio_dev));
 done:
        gpio_set_value(st->pdata->gpio_convst, 0);
        iio_trigger_notify_done(indio_dev->trig);
-       kfree(buf);
 }
 
 int ad7606_register_ring_funcs_and_init(struct iio_dev *indio_dev)