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authorOctavian Purdila <octavian.purdila@intel.com>2015-03-22 20:33:39 +0200
committerJonathan Cameron <jic23@kernel.org>2015-03-29 16:17:10 +0100
commitf4f4673b7535eff4ee1a8cfb1685fa1e1a0cb79d (patch)
treec2914fbba47032f26e1c1031e3eb17c41b2c3402 /include/linux/iio
parent37d3455672732b29a477732a94abfe95e199f0ce (diff)
iio: add support for hardware fifo
Some devices have hardware buffers that can store a number of samples for later consumption. Hardware usually provides interrupts to notify the processor when the FIFO is full or when it has reached a certain watermark level. This helps with reducing the number of interrupts to the host processor and thus it helps decreasing the power consumption. This patch enables usage of hardware FIFOs for IIO devices in conjunction with software device buffers. When the hardware FIFO is enabled the samples are stored in the hardware FIFO. The samples are later flushed to the device software buffer when the number of entries in the hardware FIFO reaches the hardware watermark or when a flush operation is triggered by the user when doing a non-blocking read on an empty software device buffer. In order to implement hardware FIFO support the device drivers must implement the following new operations: setting and getting the hardware FIFO watermark level, flushing the hardware FIFO to the software device buffer. The device must also expose information about the hardware FIFO such it's minimum and maximum watermark and if necessary a list of supported watermark values. Finally, the device driver must activate the hardware FIFO when the device buffer is enabled, if the current device settings allows it. The software device buffer watermark is passed by the IIO core to the device driver as a hint for the hardware FIFO watermark. The device driver can adjust this value to allow for hardware limitations (such as capping it to the maximum hardware watermark or adjust it to a value that is supported by the hardware). It can also disable the hardware watermark (and implicitly the hardware FIFO) it this value is below the minimum hardware watermark. Since a driver may support hardware FIFO only when not in triggered buffer mode (due to different semantics of hardware FIFO sampling and triggered sampling) this patch changes the IIO core code to allow falling back to non-triggered buffered mode if no trigger is enabled. Signed-off-by: Octavian Purdila <octavian.purdila@intel.com> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Diffstat (limited to 'include/linux/iio')
-rw-r--r--include/linux/iio/iio.h13
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 80d855061064..d86b753e9b30 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -338,6 +338,16 @@ struct iio_dev;
* provide a custom of_xlate function that reads the
* *args* and returns the appropriate index in registered
* IIO channels array.
+ * @hwfifo_set_watermark: function pointer to set the current hardware
+ * fifo watermark level; see hwfifo_* entries in
+ * Documentation/ABI/testing/sysfs-bus-iio for details on
+ * how the hardware fifo operates
+ * @hwfifo_flush_to_buffer: function pointer to flush the samples stored
+ * in the hardware fifo to the device buffer. The driver
+ * should not flush more than count samples. The function
+ * must return the number of samples flushed, 0 if no
+ * samples were flushed or a negative integer if no samples
+ * were flushed and there was an error.
**/
struct iio_info {
struct module *driver_module;
@@ -399,6 +409,9 @@ struct iio_info {
unsigned *readval);
int (*of_xlate)(struct iio_dev *indio_dev,
const struct of_phandle_args *iiospec);
+ int (*hwfifo_set_watermark)(struct iio_dev *indio_dev, unsigned val);
+ int (*hwfifo_flush_to_buffer)(struct iio_dev *indio_dev,
+ unsigned count);
};
/**