On 29/01/15 22:49, Hartmut Knaack wrote:
> Octavian Purdila schrieb am 29.01.2015 um 12:38:
>> On Thu, Jan 29, 2015 at 1:46 AM, Hartmut Knaack <knaack.h@xxxxxx> wrote:
>>>
>>> Octavian Purdila schrieb am 21.12.2014 um 01:42:
>>>> 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
>>>> threshold. This helps with reducing the number of interrupts to the
>>>> host processor and thus it helps decreasing the power consumption.
>>>>
>>>> This patch adds support for hardware fifo to IIO by allowing the
>>>> drivers to register operations for flushing the hadware fifo and
>>>> setting the watermark level.
>>>>
>>>> A driver implementing hardware fifo support must also provide a
>>>> watermark trigger which must contain "watermark" in its name.
>>>>
>>>
>>> A few comments inline, also addressed to the other IIO maintainers.
>>>
>>
>> Thanks for the review Hartmut. What do you think about the watermark
>> trigger approach?
>
> Looks good to me, so far. But keep in mind, that I am still pretty new
> to the IIO area, so people like Jonathan have a better understanding
> where the core development started out and where it should be heading.
> I will have a look at your other patches during the next days, as time
> permits.
You are under selling yourself Hartmut! Anyhow, for the 'exciting'
end of buffers, Lars is probably the most familiar with them these
days as he has a lot of out of tree code in this area (dma stuff).
Anyhow, I like the general approach, only the details that need
pinning down in my view. This is heading towards pretty much what
I always envisioned.
>
>>
>> Also, after the discussion with Jonathan I am thinking of exposing a
>> dedicated watermark level for the hardware FIFO. That way userspace
>> can set a large value for the software buffer watermark and it also
>> give control to userspace over the hardware watermark. I think that
>> control is very important to achieve a good power/latency balance.
>>
>>>> Signed-off-by: Octavian Purdila <octavian.purdila@xxxxxxxxx>
>>>> ---
>>>> Documentation/ABI/testing/sysfs-bus-iio | 22 +++++++++++++++++
>>>> drivers/iio/industrialio-buffer.c | 44 ++++++++++++++++++++++++++++-----
>>>> include/linux/iio/iio.h | 17 +++++++++++++
>>>> 3 files changed, 77 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
>>>> index 7260f1f..6bb67ac 100644
>>>> --- a/Documentation/ABI/testing/sysfs-bus-iio
>>>> +++ b/Documentation/ABI/testing/sysfs-bus-iio
>>>> @@ -1152,3 +1152,25 @@ Description:
>>>> Poll will block until the watermark is reached.
>>>> Blocking read will wait until the minimum between the requested
>>>> read amount or the low water mark is available.
>>>> + If the device has a hardware fifo this value is going to be used
>>>> + for the hardware fifo watermark as well.
>>>> +
>>>> +What: /sys/bus/iio/devices/iio:deviceX/buffer/hwfifo-length
>>>> +KernelVersion: 3.20
>>>> +Contact: linux-iio@xxxxxxxxxxxxxxx
>>>> +Description:
>>>> + A single positive integer specifying the maximum number of
>>>> + samples that the hardware fifo has. If the device does not
>>>> + support hardware fifo this is zero.
>>>> + When a device supports hardware fifo it will expose a trigger
>>>> + with the name that contains "watermark"
>>>> + (e.g. i2c-BMC150A:00-watermark-dev0).
>>>> + To use the hardware fifo the user must set an appropriate value
>>>> + in the buffer/length and buffer/low_watermark entries and select
>>>> + the watermark trigger. At that poin the hardware fifo will be
>>>> + enabled and the samples will be collected in a hardware buffer.
>>>> + When the number of samples in the hardware fifo reaches the
>>>> + watermark level the watermark trigger is issued and data is
>>>> + flushed to the devices buffer.
>>>> + A hardware buffer flush will also be triggered when reading from
>>>> + the device buffer and there is not enough data available.
>>>> \ No newline at end of file
>>>> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
>>>> index 7f74c7f..3da6d07 100644
>>>> --- a/drivers/iio/industrialio-buffer.c
>>>> +++ b/drivers/iio/industrialio-buffer.c
>>>> @@ -37,9 +37,17 @@ static bool iio_buffer_is_active(struct iio_buffer *buf)
>>>> return !list_empty(&buf->buffer_list);
>>>> }
>>>>
>>>> -static size_t iio_buffer_data_available(struct iio_buffer *buf)
>>>> +static bool iio_buffer_data_available(struct iio_dev *indio_dev,
>>>> + struct iio_buffer *buf, size_t required)
>>>> {
>>>> - return buf->access->data_available(buf);
>>>> + size_t avail = buf->access->data_available(buf);
>>>> +
>>>> + if (avail < required && indio_dev->hwfifo) {
>>>> + indio_dev->hwfifo->flush(indio_dev);
>>>> + avail = buf->access->data_available(buf);
>>>> + }
>>>> +
>>>> + return avail >= required;
>>>> }
>>>>
>>>> /**
>>>> @@ -66,13 +74,13 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
>>>>
>>>> do {
>>>> if (filp->f_flags & O_NONBLOCK) {
>>>> - if (!iio_buffer_data_available(rb)) {
>>>> + if (!iio_buffer_data_available(indio_dev, rb, 1)) {
>>>> ret = -EAGAIN;
>>>> break;
>>>> }
>>>> } else {
>>>> ret = wait_event_interruptible(rb->pollq,
>>>> - iio_buffer_data_available(rb) >= to_read ||
>>>> + iio_buffer_data_available(indio_dev, rb, to_read) ||
>>>> indio_dev->info == NULL);
>>>> if (ret)
>>>> return ret;
>>>> @@ -112,7 +120,7 @@ unsigned int iio_buffer_poll(struct file *filp,
>>>> return -ENODEV;
>>>>
>>>> poll_wait(filp, &rb->pollq, wait);
>>>> - if (iio_buffer_data_available(rb) >= rb->low_watermark)
>>>> + if (iio_buffer_data_available(indio_dev, rb, rb->low_watermark))
>>>> return POLLIN | POLLRDNORM;
>>>> return 0;
>>>> }
>>>> @@ -440,8 +448,14 @@ static ssize_t iio_buffer_write_length(struct device *dev,
>>>> if (buffer->length)
>>>> val = buffer->length;
>>>>
>>>> - if (val < buffer->low_watermark)
>>>> + if (val < buffer->low_watermark) {
>>>> + if (indio_dev->hwfifo) {
>>>> + ret = indio_dev->hwfifo->set_watermark(indio_dev, val);
>>>> + if (ret)
>>>> + return ret;
>>>> + }
>>>> buffer->low_watermark = val;
>>>> + }
>>>>
>>>> return len;
>>>> }
>>>> @@ -811,6 +825,12 @@ static ssize_t iio_buffer_store_watermark(struct device *dev,
>>>> goto out;
>>>> }
>>>>
>>>> + if (indio_dev->hwfifo) {
>>>> + ret = indio_dev->hwfifo->set_watermark(indio_dev, val);
>>>> + if (ret)
>>>> + goto out;
>>>> + }
>>>> +
>>>> buffer->low_watermark = val;
>>>> ret = 0;
>>>> out:
>>>> @@ -818,6 +838,16 @@ out:
>>>> return ret ? ret : len;
>>>> }
>>>>
>>>> +ssize_t iio_buffer_hwfifo_read_length(struct device *dev,
>>>> + struct device_attribute *attr,
>>>> + char *buf)
>>>> +{
>>>> + struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>>>> + const struct iio_hwfifo *hwfifo = indio_dev->hwfifo;
>>>> +
>>>> + return sprintf(buf, "%u\n", hwfifo ? hwfifo->length : 0);
>>>> +}
>>>> +
>>>> static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
>>>> iio_buffer_write_length);
>>>> static struct device_attribute dev_attr_length_ro = __ATTR(length,
>>>> @@ -826,11 +856,13 @@ static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
>>>> iio_buffer_show_enable, iio_buffer_store_enable);
>>>> static DEVICE_ATTR(low_watermark, S_IRUGO | S_IWUSR,
>>>> iio_buffer_show_watermark, iio_buffer_store_watermark);
>>>> +static DEVICE_ATTR(hwfifo_length, S_IRUGO, iio_buffer_hwfifo_read_length, NULL);
>>>>
>>>> static struct attribute *iio_buffer_attrs[] = {
>>>> &dev_attr_length.attr,
>>>> &dev_attr_enable.attr,
>>>> &dev_attr_low_watermark.attr,
>>>> + &dev_attr_hwfifo_length.attr,
>>>> };
>>>>
>>>> int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
>>>> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
>>>> index 878d861..f64a05f 100644
>>>> --- a/include/linux/iio/iio.h
>>>> +++ b/include/linux/iio/iio.h
>>>> @@ -417,6 +417,22 @@ struct iio_buffer_setup_ops {
>>>> };
>>>>
>>>> /**
>>>> + * struct iio_buffer_hwfifo_ops - hardware fifo operations
>>>> + *
>>>> + * @length: [DRIVER] the hardware fifo length
>>>> + * @set_watermark: [DRIVER] setups the watermark level
>>> Maybe use "sets" instead of "setups".
>>>
>>
>> Ok, sensible suggestion, I'll do that in the next version.
>>
>>> Also, and this is more a general question, as it was quite annoying when getting into
>>> the topic: I would prefer to place some information about the expected return values of
>>> these functions into these descriptions. What do you guys think about that?
>>>
>>>> + * @flush: [DRIVER] copies data from the hardware buffer to the
>>>> + * device buffer
>>>> + * @watermark_trig: [DRIVER] an allocated and registered trigger containing
>>>> + * "watermark" in its name
>>>> + */
>>>> +struct iio_hwfifo {
>>>> + int length;
>>>> + int (*set_watermark)(struct iio_dev *, unsigned int);
>>>> + int (*flush)(struct iio_dev *);
>>>> +};
>>>> +
>>>> +/**
>>>> * struct iio_dev - industrial I/O device
>>>> * @id: [INTERN] used to identify device internally
>>>> * @modes: [DRIVER] operating modes supported by device
>>>> @@ -491,6 +507,7 @@ struct iio_dev {
>>>> int groupcounter;
>>>>
>>>> unsigned long flags;
>>>> + const struct iio_hwfifo *hwfifo;
>>> This new entry should be added to the description of the iio_dev struct, as well.
>>
>> Sure.
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe linux-iio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
