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Date: Fri, 2 Mar 2012 14:21:49 +0100 (CET)
From: Guennadi Liakhovetski <g.liakhovetski@....de>
To: linux-kernel@...r.kernel.org
cc: Vinod Koul <vinod.koul@...el.com>
Subject: Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel()
Hi Vinod
On Wed, 1 Feb 2012, Guennadi Liakhovetski wrote:
> When performing slame DMA some dmaengine drivers need additional data from
> client drivers to find out, whether they can support that specific client
> and to configure the DMA channel for it. This additional data has to be
> supplied by client drivers during channel allocation, i.e., with the
> __dma_request_channel() function. This patch adds a new
> struct dma_slave_desc with some basic data in it, further this struct can
> be embedded in hardware-specific types to supply any auxiliary
> configuration.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@....de>
What do you think about this patch? It would be important for me to know
your opinion, resp., to get it approved by you, then I could base my other
shdma / "simple" dma work on top of it. It would also give me a "natural"
way to eliminate the use of the .priv pointer in shdma.
Thanks
Guennadi
> ---
>
> Vinod, this is the patch I told you about. It also requires changing all
> dmaengine drivers by adding one parameter to their
> .device_alloc_chan_resources() methods, which they would simply continue
> to ignore. Since this patch doesn't include that modification, it is
> marked as an RFC.
>
> drivers/dma/dmaengine.c | 14 ++++++++------
> include/linux/dmaengine.h | 16 ++++++++++++----
> 2 files changed, 20 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index 139d418..0eb03b8 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -204,10 +204,11 @@ static void balance_ref_count(struct dma_chan *chan)
> /**
> * dma_chan_get - try to grab a dma channel's parent driver module
> * @chan - channel to grab
> + * @slave - optional DMA slave specification
> *
> * Must be called under dma_list_mutex
> */
> -static int dma_chan_get(struct dma_chan *chan)
> +static int dma_chan_get(struct dma_chan *chan, struct dma_slave_desc *slave)
> {
> struct module *owner = dma_chan_to_owner(chan);
>
> @@ -220,7 +221,7 @@ static int dma_chan_get(struct dma_chan *chan)
>
> /* allocate upon first client reference */
> if (chan->client_count == 1) {
> - int desc_cnt = chan->device->device_alloc_chan_resources(chan);
> + int desc_cnt = chan->device->device_alloc_chan_resources(chan, slave);
>
> if (desc_cnt < 0) {
> chan->client_count = 0;
> @@ -482,7 +483,8 @@ static struct dma_chan *private_candidate(dma_cap_mask_t *mask, struct dma_devic
> * @fn: optional callback to disposition available channels
> * @fn_param: opaque parameter to pass to dma_filter_fn
> */
> -struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param)
> +struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param,
> + struct dma_slave_desc *slave)
> {
> struct dma_device *device, *_d;
> struct dma_chan *chan = NULL;
> @@ -500,7 +502,7 @@ struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, v
> */
> dma_cap_set(DMA_PRIVATE, device->cap_mask);
> device->privatecnt++;
> - err = dma_chan_get(chan);
> + err = dma_chan_get(chan, slave);
>
> if (err == -ENODEV) {
> pr_debug("%s: %s module removed\n", __func__,
> @@ -555,7 +557,7 @@ void dmaengine_get(void)
> if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
> continue;
> list_for_each_entry(chan, &device->channels, device_node) {
> - err = dma_chan_get(chan);
> + err = dma_chan_get(chan, NULL);
> if (err == -ENODEV) {
> /* module removed before we could use it */
> list_del_rcu(&device->global_node);
> @@ -762,7 +764,7 @@ int dma_async_device_register(struct dma_device *device)
> /* if clients are already waiting for channels we need
> * to take references on their behalf
> */
> - if (dma_chan_get(chan) == -ENODEV) {
> + if (dma_chan_get(chan, NULL) == -ENODEV) {
> /* note we can only get here for the first
> * channel as the remaining channels are
> * guaranteed to get a reference
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 679b349..8164007 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -412,6 +412,10 @@ struct dma_async_tx_descriptor {
> #endif
> };
>
> +struct dma_slave_desc {
> + unsigned int id;
> +};
> +
> #ifndef CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH
> static inline void txd_lock(struct dma_async_tx_descriptor *txd)
> {
> @@ -541,7 +545,8 @@ struct dma_device {
> int dev_id;
> struct device *dev;
>
> - int (*device_alloc_chan_resources)(struct dma_chan *chan);
> + int (*device_alloc_chan_resources)(struct dma_chan *chan,
> + struct dma_slave_desc *slave);
> void (*device_free_chan_resources)(struct dma_chan *chan);
>
> struct dma_async_tx_descriptor *(*device_prep_dma_memcpy)(
> @@ -922,7 +927,8 @@ enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie);
> #ifdef CONFIG_DMA_ENGINE
> enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
> void dma_issue_pending_all(void);
> -struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);
> +struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param,
> + struct dma_slave_desc *slave);
> void dma_release_channel(struct dma_chan *chan);
> #else
> static inline enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
> @@ -933,7 +939,7 @@ static inline void dma_issue_pending_all(void)
> {
> }
> static inline struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask,
> - dma_filter_fn fn, void *fn_param)
> + dma_filter_fn fn, void *fn_param, struct dma_slave_desc *slave)
> {
> return NULL;
> }
> @@ -948,7 +954,9 @@ int dma_async_device_register(struct dma_device *device);
> void dma_async_device_unregister(struct dma_device *device);
> void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
> struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
> -#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
> +#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y, NULL)
> +#define dma_request_slave_channel(mask, x, y, id) __dma_request_channel(&(mask), \
> + x, y, id)
>
> /* --- Helper iov-locking functions --- */
>
> --
> 1.7.2.5
>
> --
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---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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