Date:	Fri, 14 Sep 2012 15:09:25 +0530
From:	Vinod Koul <vinod.koul@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	Dan Williams <djbw@...com>, Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, linus.walleij@...aro.org,
	Jon Hunter <jon-hunter@...com>,
	Stephen Warren <swarren@...dia.com>,
	Benoit Cousson <b-cousson@...com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Sascha Hauer <kernel@...gutronix.de>,
	Kukjin Kim <kgene.kim@...sung.com>,
	viresh kumar <viresh.kumar@...aro.org>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [RFC] dmaengine: add dmanegine slave map api's

On Fri, 2012-09-14 at 15:03 +0530, Vinod Koul wrote:

Sorry, this is a RFC, and not a PATCH yet.

> when allocating a channel the dmaengine finds first channel that matches the
> mask and calls filter function
> In slave dmaengine model, there already exists a mapping, either hardwired in
> SoC or thru a configurable mux. So we typically need channel from controller X
> and in same cases a partcular channel Y.
> 
> Add new APIs which allow adding channel map for client-dma relationship.
> This mapping needs to be registered with dmaengine by platform specfic code
> which is aware of this mapping. This mapping needs to be added _before_ any
> client tries to access a channel.
> 
> Then in order for slave devices to get a channel based on above mapping, add new
> slave specfic dmanengine channel request/free APIs
> 
> Signed-off-by: Vinod Koul <vinod.koul@...ux.intel.com>
> ---
> this is the first attempt to do the slave dma mapping, we have been discussing
> this and we all agree to need for this. This is the same patch which was shown
> at KS and attempts to build the mapping information within dmaengine which is
> platform and arch agnostic.
> 
> The arch code like DT/board-files/SFI etc can use these APIs to build dmaengine
> mapping and then dmaengine filters channels based on this mapping.
> 
> Now Credits:
> the orginal idea was from Linus Walleij and has been discussed in similar
> format.
> ---
>  drivers/dma/dmaengine.c   |  152 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/dmaengine.h |   50 +++++++++++++++
>  2 files changed, 202 insertions(+)
> 
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index 3491654..293dfd0 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -1066,6 +1066,158 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
>  }
>  EXPORT_SYMBOL_GPL(dma_run_dependencies);
>  
> +/* slave channel mapping code*/
> +static LIST_HEAD(dma_slave_map);
> +
> +/*called under lock held */
> +static struct dma_chan *dmaengine_get_slave_channel(char *requestor, dma_cap_mask_t *mask)
> +{
> +
> +	struct dma_device *device, *_d;
> +	struct dma_chan *chan = NULL;
> +	int err;
> +
> +	list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
> +		if (strcmp(requestor, dev_name(device->dev)))
> +			continue;
> +
> +		chan = private_candidate(mask, device, NULL, NULL);
> +		if (chan) {
> +			/* Found a suitable channel, try to grab, prep, and
> +			 * return it.  We first set DMA_PRIVATE to disable
> +			 * balance_ref_count as this channel will not be
> +			 * published in the general-purpose allocator
> +			 */
> +			dma_cap_set(DMA_PRIVATE, device->cap_mask);
> +			device->privatecnt++;
> +			err = dma_chan_get(chan);
> +
> +			if (err == -ENODEV) {
> +				pr_debug("%s: %s module removed\n",
> +					 __func__, dma_chan_name(chan));
> +				list_del_rcu(&device->global_node);
> +			} else if (err)
> +				pr_debug("%s: failed to get %s: (%d)\n",
> +					 __func__, dma_chan_name(chan), err);
> +			else
> +				break;
> +			if (--device->privatecnt == 0)
> +				dma_cap_clear(DMA_PRIVATE, device->cap_mask);
> +			chan = NULL;
> +		}
> +	}
> +	return chan;
> +}
> +
> +/**
> + * dmaengine_request_slave_channel - request a slave channel for which damengine
> + * knows the channel mapping
> + *
> + * This is generic API which should work on all arch and doesnt assume any arch
> + * implementation of how map is constructed. Arch code should call map apis to
> + * build the channel map first
> + *
> + * @requestor: client name
> + * @config: dma_slave_config, this is set post channle allocation
> + * @mask: capabilities that the channel must satisfy
> + * @fn: optional filter function should be unused typically
> + * @fn_param: filter fn params
> + */
> +struct dma_chan *dmaengine_request_slave_channel(
> +		char *requestor, struct dma_slave_config *config,
> +		dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param)
> +{
> +	struct dma_chan *slave = NULL;
> +	struct dmaengine_slave_map_entries *entry, *_e;
> +
> +	/* perhpas we dont need mask arg, it should be slave anyway */
> +	if (!__dma_has_cap(DMA_SLAVE, mask))
> +		return NULL;
> +
> +	mutex_lock(&dma_list_mutex);
> +	/* find a channel which maps to this request */
> +	list_for_each_entry_safe(entry, _e, &dma_slave_map, node) {
> +		if (strcmp(requestor, entry->map->client))
> +			continue;
> +
> +		/* have we already allocated this mapping */
> +		if (entry->used == true)
> +			continue;
> +
> +		/* now we hit an entry in map,
> +		 * see if we can get a channel in controller */
> +		slave = dmaengine_get_slave_channel(requestor, mask);
> +		if (!slave)
> +			continue;
> +
> +		/* check if client is requesting some specfic slave channel */
> +		if ((entry->map->ch != -1) && (entry->map->ch != slave->chan_id))
> +			continue;
> +
> +		/* now call filter fn but it should not be used anyway */
> +		if (fn && !fn(slave, fn_param))
> +			continue;
> +
> +		entry->used = true;
> +		mutex_unlock(&dma_list_mutex);
> +
> +		/* pick slave id from map if not set */
> +		if (!config->slave_id)
> +			config->slave_id = entry->map->slave_id;
> +
> +		/*now lets set slave params */
> +		dmaengine_slave_config(slave, config);
> +
> +		return slave;
> +	}
> +	mutex_unlock(&dma_list_mutex);
> +	return NULL;
> +}
> +EXPORT_SYMBOL_GPL(dmaengine_request_slave_channel);
> +
> +int dmaengine_add_channel_map(struct dmaengine_slave_map *map,
> +		unsigned int num_entries)
> +{
> +	int i = 0;
> +	struct dmaengine_slave_map_entries *entry;
> +
> +	entry = kzalloc(sizeof(struct dmaengine_slave_map) * num_entries, GFP_KERNEL);
> +	if (entry == NULL)
> +		return -ENOMEM;
> +	entry->num_entries = num_entries;
> +	mutex_lock(&dma_list_mutex);
> +	for (i = 0; i < num_entries; i++) {
> +		entry->map = map;
> +		entry->used = false;
> +		entry->map->entry = entry;
> +		list_add_tail(&entry->node, &dma_slave_map);
> +		entry++;
> +		map++;
> +	}
> +	mutex_unlock(&dma_list_mutex);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(dmaengine_add_channel_map);
> +
> +void dmaengine_free_channel_map(struct dmaengine_slave_map *map)
> +{
> +	struct dmaengine_slave_map_entries *entry;
> +	unsigned int i, num_entries;
> +
> +	BUG_ON(map);
> +	mutex_lock(&dma_list_mutex);
> +	entry = map->entry;
> +	num_entries = entry->num_entries;
> +	for (i = 0; i < num_entries; i++) {
> +		list_del(&entry->node);
> +		entry++;
> +	}
> +	kfree(entry);
> +	mutex_unlock(&dma_list_mutex);
> +	return;
> +}
> +EXPORT_SYMBOL_GPL(dmaengine_free_channel_map);
> +
>  static int __init dma_bus_init(void)
>  {
>  	return class_register(&dma_devclass);
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 9c02a45..54dd1d5 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -371,6 +371,35 @@ struct dma_slave_config {
>  	unsigned int slave_id;
>  };
>  
> +struct dmaengine_slave_map_entries;
> +/* dmaengine slave channel map
> + *
> + * @dma: dma controller, mandatory
> + * @client: clinet associated with the controller, mandatory
> + * @ch: channel index, desired but optional
> + * @slave_id: slave id for programming mux
> + *
> + * the platform needs to tell the channel mapping information to the dmaengine
> + * code thru this structure.
> + * This is used by dmanengine to find the channel to be allocated during
> + * dma_rquest_channel process for slave channels
> + */
> +struct dmaengine_slave_map {
> +	char *dma;
> +	char *client;
> +	int ch;
> +	int slave_id;
> +	struct dmaengine_slave_map_entries *entry;
> +};
> +
> +struct dmaengine_slave_map_entries {
> +	struct dmaengine_slave_map *map;
> +	bool used;
> +	struct list_head node;
> +	unsigned int num_entries;
> +};
> +
> +
>  static inline const char *dma_chan_name(struct dma_chan *chan)
>  {
>  	return dev_name(&chan->dev->device);
> @@ -974,6 +1003,12 @@ 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);
>  void dma_release_channel(struct dma_chan *chan);
> +struct dma_chan *dmaengine_request_slave_channel(
> +		char *requestor, struct dma_slave_config *config,
> +		dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param);
> +int dmaengine_add_channel_map(struct dmaengine_slave_map *map,
> +		unsigned int num_entries);
> +void dmaengine_free_channel_map(struct dmaengine_slave_map *map);
>  #else
>  static inline enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
>  {
> @@ -990,6 +1025,21 @@ static inline struct dma_chan *__dma_request_channel(dma_cap_mask_t *mask,
>  static inline void dma_release_channel(struct dma_chan *chan)
>  {
>  }
> +struct dma_chan *dmaengine_request_slave_channel(
> +		char *requestor, struct dma_slave_config *config,
> +		dma_cap_mask_t *mask, dma_filter_fn fn, void *fn_param)
> +{
> +	return NULL;
> +}
> +static inline int dmaengine_add_channel_map(struct dmaengine_slave_map *map,
> +		unsigned int num_entries)
> +{
> +	return -EIO;
> +}
> +void dmaengine_free_channel_map(struct dmaengine_slave_map *map)
> +{
> +	return;
> +}
>  #endif
>  
>  /* --- DMA device --- */


-- 
~Vinod

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