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Message-ID: <1538e69e5d36405d8d27de1140f5c9197c91e0d6.camel@gmail.com>
Date: Tue, 17 Dec 2024 12:50:05 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: David Lechner <dlechner@...libre.com>, Mark Brown <broonie@...nel.org>,
Jonathan Cameron
<jic23@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
<krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Nuno
Sá
<nuno.sa@...log.com>
Cc: Uwe Kleine-König <ukleinek@...nel.org>, Michael
Hennerich <Michael.Hennerich@...log.com>, Lars-Peter Clausen
<lars@...afoo.de>, David Jander <david@...tonic.nl>, Martin Sperl
<kernel@...tin.sperl.org>, linux-spi@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-iio@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v6 08/17] iio: buffer-dmaengine: split requesting DMA
channel from allocating buffer
On Wed, 2024-12-11 at 14:54 -0600, David Lechner wrote:
> Refactor the IIO dmaengine buffer code to split requesting the DMA
> channel from allocating the buffer. We want to be able to add a new
> function where the IIO device driver manages the DMA channel, so these
> two actions need to be separate.
>
> To do this, calling dma_request_chan() is moved from
> iio_dmaengine_buffer_alloc() to iio_dmaengine_buffer_setup_ext(). A new
> __iio_dmaengine_buffer_setup_ext() helper function is added to simplify
> error unwinding and will also be used by a new function in a later
> patch.
>
> iio_dmaengine_buffer_free() now only frees the buffer and does not
> release the DMA channel. A new iio_dmaengine_buffer_teardown() function
> is added to unwind everything done in iio_dmaengine_buffer_setup_ext().
> This keeps things more symmetrical with obvious pairs alloc/free and
> setup/teardown.
>
> Calling dma_get_slave_caps() in iio_dmaengine_buffer_alloc() is moved so
> that we can avoid any gotos for error unwinding.
>
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
Reviewed-by: Nuno Sa <nuno.sa@...log.com>
>
> v6 changes:
> * Split out from patch that adds the new function
> * Dropped owns_chan flag
> * Introduced iio_dmaengine_buffer_teardown() so that
> iio_dmaengine_buffer_free() doesn't have to manage the DMA channel
> ---
> drivers/iio/adc/adi-axi-adc.c | 2 +-
> drivers/iio/buffer/industrialio-buffer-dmaengine.c | 106 ++++++++++++--------
> -
> drivers/iio/dac/adi-axi-dac.c | 2 +-
> include/linux/iio/buffer-dmaengine.h | 2 +-
> 4 files changed, 65 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/iio/adc/adi-axi-adc.c b/drivers/iio/adc/adi-axi-adc.c
> index
> c7357601f0f869e57636f00bb1e26c059c3ab15c..a55db308baabf7b26ea98431cab1e6af7fe2
> a5f3 100644
> --- a/drivers/iio/adc/adi-axi-adc.c
> +++ b/drivers/iio/adc/adi-axi-adc.c
> @@ -305,7 +305,7 @@ static struct iio_buffer *axi_adc_request_buffer(struct
> iio_backend *back,
> static void axi_adc_free_buffer(struct iio_backend *back,
> struct iio_buffer *buffer)
> {
> - iio_dmaengine_buffer_free(buffer);
> + iio_dmaengine_buffer_teardown(buffer);
> }
>
> static int axi_adc_reg_access(struct iio_backend *back, unsigned int reg,
> diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> index
> 614e1c4189a9cdd5a8d9d8c5ef91566983032951..02847d3962fcbb43ec76167db6482ab951f2
> 0942 100644
> --- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> +++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
> @@ -206,39 +206,29 @@ static const struct iio_dev_attr
> *iio_dmaengine_buffer_attrs[] = {
>
> /**
> * iio_dmaengine_buffer_alloc() - Allocate new buffer which uses DMAengine
> - * @dev: DMA channel consumer device
> - * @channel: DMA channel name, typically "rx".
> + * @chan: DMA channel.
> *
> * This allocates a new IIO buffer which internally uses the DMAengine
> framework
> - * to perform its transfers. The parent device will be used to request the
> DMA
> - * channel.
> + * to perform its transfers.
> *
> * Once done using the buffer iio_dmaengine_buffer_free() should be used to
> * release it.
> */
> -static struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
> - const char *channel)
> +static struct iio_buffer *iio_dmaengine_buffer_alloc(struct dma_chan *chan)
> {
> struct dmaengine_buffer *dmaengine_buffer;
> unsigned int width, src_width, dest_width;
> struct dma_slave_caps caps;
> - struct dma_chan *chan;
> int ret;
>
> + ret = dma_get_slave_caps(chan, &caps);
> + if (ret < 0)
> + return ERR_PTR(ret);
> +
> dmaengine_buffer = kzalloc(sizeof(*dmaengine_buffer), GFP_KERNEL);
> if (!dmaengine_buffer)
> return ERR_PTR(-ENOMEM);
>
> - chan = dma_request_chan(dev, channel);
> - if (IS_ERR(chan)) {
> - ret = PTR_ERR(chan);
> - goto err_free;
> - }
> -
> - ret = dma_get_slave_caps(chan, &caps);
> - if (ret < 0)
> - goto err_release;
> -
> /* Needs to be aligned to the maximum of the minimums */
> if (caps.src_addr_widths)
> src_width = __ffs(caps.src_addr_widths);
> @@ -262,12 +252,6 @@ static struct iio_buffer
> *iio_dmaengine_buffer_alloc(struct device *dev,
> dmaengine_buffer->queue.buffer.access = &iio_dmaengine_buffer_ops;
>
> return &dmaengine_buffer->queue.buffer;
> -
> -err_release:
> - dma_release_channel(chan);
> -err_free:
> - kfree(dmaengine_buffer);
> - return ERR_PTR(ret);
> }
>
> /**
> @@ -276,17 +260,57 @@ static struct iio_buffer
> *iio_dmaengine_buffer_alloc(struct device *dev,
> *
> * Frees a buffer previously allocated with iio_dmaengine_buffer_alloc().
> */
> -void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
> +static void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
> {
> struct dmaengine_buffer *dmaengine_buffer =
> iio_buffer_to_dmaengine_buffer(buffer);
>
> iio_dma_buffer_exit(&dmaengine_buffer->queue);
> - dma_release_channel(dmaengine_buffer->chan);
> -
> iio_buffer_put(buffer);
> }
> -EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_free, "IIO_DMAENGINE_BUFFER");
> +
> +/**
> + * iio_dmaengine_buffer_teardown() - Releases DMA channel and frees buffer
> + * @buffer: Buffer to free
> + *
> + * Releases the DMA channel and frees the buffer previously setup with
> + * iio_dmaengine_buffer_setup_ext().
> + */
> +void iio_dmaengine_buffer_teardown(struct iio_buffer *buffer)
> +{
> + struct dmaengine_buffer *dmaengine_buffer =
> + iio_buffer_to_dmaengine_buffer(buffer);
> + struct dma_chan *chan = dmaengine_buffer->chan;
> +
> + iio_dmaengine_buffer_free(buffer);
> + dma_release_channel(chan);
> +}
> +EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_teardown, "IIO_DMAENGINE_BUFFER");
> +
> +static struct iio_buffer
> +*__iio_dmaengine_buffer_setup_ext(struct iio_dev *indio_dev,
> + struct dma_chan *chan,
> + enum iio_buffer_direction dir)
> +{
> + struct iio_buffer *buffer;
> + int ret;
> +
> + buffer = iio_dmaengine_buffer_alloc(chan);
> + if (IS_ERR(buffer))
> + return ERR_CAST(buffer);
> +
> + indio_dev->modes |= INDIO_BUFFER_HARDWARE;
> +
> + buffer->direction = dir;
> +
> + ret = iio_device_attach_buffer(indio_dev, buffer);
> + if (ret) {
> + iio_dmaengine_buffer_free(buffer);
> + return ERR_PTR(ret);
> + }
> +
> + return buffer;
> +}
>
> /**
> * iio_dmaengine_buffer_setup_ext() - Setup a DMA buffer for an IIO device
> @@ -300,7 +324,7 @@ EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_free,
> "IIO_DMAENGINE_BUFFER");
> * It also appends the INDIO_BUFFER_HARDWARE mode to the supported modes of
> the
> * IIO device.
> *
> - * Once done using the buffer iio_dmaengine_buffer_free() should be used to
> + * Once done using the buffer iio_dmaengine_buffer_teardown() should be used
> to
> * release it.
> */
> struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
> @@ -308,30 +332,24 @@ struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct
> device *dev,
> const char *channel,
> enum iio_buffer_direction
> dir)
> {
> + struct dma_chan *chan;
> struct iio_buffer *buffer;
> - int ret;
> -
> - buffer = iio_dmaengine_buffer_alloc(dev, channel);
> - if (IS_ERR(buffer))
> - return ERR_CAST(buffer);
> -
> - indio_dev->modes |= INDIO_BUFFER_HARDWARE;
>
> - buffer->direction = dir;
> + chan = dma_request_chan(dev, channel);
> + if (IS_ERR(chan))
> + return ERR_CAST(chan);
>
> - ret = iio_device_attach_buffer(indio_dev, buffer);
> - if (ret) {
> - iio_dmaengine_buffer_free(buffer);
> - return ERR_PTR(ret);
> - }
> + buffer = __iio_dmaengine_buffer_setup_ext(indio_dev, chan, dir);
> + if (IS_ERR(buffer))
> + dma_release_channel(chan);
>
> return buffer;
> }
> EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_setup_ext, "IIO_DMAENGINE_BUFFER");
>
> -static void __devm_iio_dmaengine_buffer_free(void *buffer)
> +static void devm_iio_dmaengine_buffer_teardown(void *buffer)
> {
> - iio_dmaengine_buffer_free(buffer);
> + iio_dmaengine_buffer_teardown(buffer);
> }
>
> /**
> @@ -357,7 +375,7 @@ int devm_iio_dmaengine_buffer_setup_ext(struct device
> *dev,
> if (IS_ERR(buffer))
> return PTR_ERR(buffer);
>
> - return devm_add_action_or_reset(dev,
> __devm_iio_dmaengine_buffer_free,
> + return devm_add_action_or_reset(dev,
> devm_iio_dmaengine_buffer_teardown,
> buffer);
> }
> EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_ext,
> "IIO_DMAENGINE_BUFFER");
> diff --git a/drivers/iio/dac/adi-axi-dac.c b/drivers/iio/dac/adi-axi-dac.c
> index
> b143f7ed6847277aeb49094627d90e5d95eed71c..5d5157af0a233143daff906b699bdae10f36
> 8867 100644
> --- a/drivers/iio/dac/adi-axi-dac.c
> +++ b/drivers/iio/dac/adi-axi-dac.c
> @@ -168,7 +168,7 @@ static struct iio_buffer *axi_dac_request_buffer(struct
> iio_backend *back,
> static void axi_dac_free_buffer(struct iio_backend *back,
> struct iio_buffer *buffer)
> {
> - iio_dmaengine_buffer_free(buffer);
> + iio_dmaengine_buffer_teardown(buffer);
> }
>
> enum {
> diff --git a/include/linux/iio/buffer-dmaengine.h b/include/linux/iio/buffer-
> dmaengine.h
> index
> 81d9a19aeb9199dd58bb9d35a91f0ec4b00846df..72a2e3fd8a5bf5e8f27ee226ddd92979d233
> 754b 100644
> --- a/include/linux/iio/buffer-dmaengine.h
> +++ b/include/linux/iio/buffer-dmaengine.h
> @@ -12,7 +12,7 @@
> struct iio_dev;
> struct device;
>
> -void iio_dmaengine_buffer_free(struct iio_buffer *buffer);
> +void iio_dmaengine_buffer_teardown(struct iio_buffer *buffer);
> struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
> struct iio_dev *indio_dev,
> const char *channel,
>
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