dmaengine: core: Introduce new, universal API to request a channel

The two API function can cover most, if not all current APIs used to
request a channel. With minimal effort dmaengine drivers, platforms and
dmaengine user drivers can be converted to use the two function.

struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask);

To request any channel matching with the requested capabilities, can be
used to request channel for memcpy, memset, xor, etc where no hardware
synchronization is needed.

struct dma_chan *dma_request_chan(struct device *dev, const char *name);
To request a slave channel. The dma_request_chan() will try to find the
channel via DT, ACPI or in case if the kernel booted in non DT/ACPI mode
it will use a filter lookup table and retrieves the needed information from
the dma_slave_map provided by the DMA drivers.
This legacy mode needs changes in platform code, in dmaengine drivers and
finally the dmaengine user drivers can be converted:

For each dmaengine driver an array of DMA device, slave and the parameter
for the filter function needs to be added:

static const struct dma_slave_map da830_edma_map[] = {
	{ "davinci-mcasp.0", "rx", EDMA_FILTER_PARAM(0, 0) },
	{ "davinci-mcasp.0", "tx", EDMA_FILTER_PARAM(0, 1) },
	{ "davinci-mcasp.1", "rx", EDMA_FILTER_PARAM(0, 2) },
	{ "davinci-mcasp.1", "tx", EDMA_FILTER_PARAM(0, 3) },
	{ "davinci-mcasp.2", "rx", EDMA_FILTER_PARAM(0, 4) },
	{ "davinci-mcasp.2", "tx", EDMA_FILTER_PARAM(0, 5) },
	{ "spi_davinci.0", "rx", EDMA_FILTER_PARAM(0, 14) },
	{ "spi_davinci.0", "tx", EDMA_FILTER_PARAM(0, 15) },
	{ "da830-mmc.0", "rx", EDMA_FILTER_PARAM(0, 16) },
	{ "da830-mmc.0", "tx", EDMA_FILTER_PARAM(0, 17) },
	{ "spi_davinci.1", "rx", EDMA_FILTER_PARAM(0, 18) },
	{ "spi_davinci.1", "tx", EDMA_FILTER_PARAM(0, 19) },
};

This information is going to be needed by the dmaengine driver, so
modification to the platform_data is needed, and the driver map should be
added to the pdata of the DMA driver:

da8xx_edma0_pdata.slave_map = da830_edma_map;
da8xx_edma0_pdata.slavecnt = ARRAY_SIZE(da830_edma_map);

The DMA driver then needs to configure the needed device -> filter_fn
mapping before it registers with dma_async_device_register() :

ecc->dma_slave.filter_map.map = info->slave_map;
ecc->dma_slave.filter_map.mapcnt = info->slavecnt;
ecc->dma_slave.filter_map.fn = edma_filter_fn;

When neither DT or ACPI lookup is available the dma_request_chan() will
try to match the requester's device name with the filter_map's list of
device names, when a match found it will use the information from the
dma_slave_map to get the channel with the dma_get_channel() internal
function.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 77 insertions, 12 deletions

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 81a36fc..a094dbb 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -43,6 +43,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/platform_device.h>
 #include <linux/dma-mapping.h>
 #include <linux/init.h>
 #include <linux/module.h>
@@ -665,27 +666,73 @@ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
 }
 EXPORT_SYMBOL_GPL(__dma_request_channel);
 
+static const struct dma_slave_map *dma_filter_match(struct dma_device *device,
+						    const char *name,
+						    struct device *dev)
+{
+	int i;
+
+	if (!device->filter.mapcnt)
+		return NULL;
+
+	for (i = 0; i < device->filter.mapcnt; i++) {
+		const struct dma_slave_map *map = &device->filter.map[i];
+
+		if (!strcmp(map->devname, dev_name(dev)) &&
+		    !strcmp(map->slave, name))
+			return map;
+	}
+
+	return NULL;
+}
+
 /**
- * dma_request_slave_channel_reason - try to allocate an exclusive slave channel
+ * dma_request_chan - try to allocate an exclusive slave channel
  * @dev:	pointer to client device structure
  * @name:	slave channel name
  *
  * Returns pointer to appropriate DMA channel on success or an error pointer.
  */
-struct dma_chan *dma_request_slave_channel_reason(struct device *dev,
-						  const char *name)
+struct dma_chan *dma_request_chan(struct device *dev, const char *name)
 {
+	struct dma_device *d, *_d;
+	struct dma_chan *chan = NULL;
+
 	/* If device-tree is present get slave info from here */
 	if (dev->of_node)
-		return of_dma_request_slave_channel(dev->of_node, name);
+		chan = of_dma_request_slave_channel(dev->of_node, name);
 
 	/* If device was enumerated by ACPI get slave info from here */
-	if (ACPI_HANDLE(dev))
-		return acpi_dma_request_slave_chan_by_name(dev, name);
+	if (has_acpi_companion(dev) && !chan)
+		chan = acpi_dma_request_slave_chan_by_name(dev, name);
+
+	if (chan) {
+		/* Valid channel found or requester need to be deferred */
+		if (!IS_ERR(chan) || PTR_ERR(chan) == -EPROBE_DEFER)
+			return chan;
+	}
+
+	/* Try to find the channel via the DMA filter map(s) */
+	mutex_lock(&dma_list_mutex);
+	list_for_each_entry_safe(d, _d, &dma_device_list, global_node) {
+		dma_cap_mask_t mask;
+		const struct dma_slave_map *map = dma_filter_match(d, name, dev);
+
+		if (!map)
+			continue;
+
+		dma_cap_zero(mask);
+		dma_cap_set(DMA_SLAVE, mask);
 
-	return ERR_PTR(-ENODEV);
+		chan = find_candidate(d, &mask, d->filter.fn, map->param);
+		if (!IS_ERR(chan))
+			break;
+	}
+	mutex_unlock(&dma_list_mutex);
+
+	return chan ? chan : ERR_PTR(-EPROBE_DEFER);
 }
-EXPORT_SYMBOL_GPL(dma_request_slave_channel_reason);
+EXPORT_SYMBOL_GPL(dma_request_chan);
 
 /**
  * dma_request_slave_channel - try to allocate an exclusive slave channel
@@ -697,17 +744,35 @@ EXPORT_SYMBOL_GPL(dma_request_slave_channel_reason);
 struct dma_chan *dma_request_slave_channel(struct device *dev,
 					   const char *name)
 {
-	struct dma_chan *ch = dma_request_slave_channel_reason(dev, name);
+	struct dma_chan *ch = dma_request_chan(dev, name);
 	if (IS_ERR(ch))
 		return NULL;
 
-	dma_cap_set(DMA_PRIVATE, ch->device->cap_mask);
-	ch->device->privatecnt++;
-
 	return ch;
 }
 EXPORT_SYMBOL_GPL(dma_request_slave_channel);
 
+/**
+ * dma_request_chan_by_mask - allocate a channel satisfying certain capabilities
+ * @mask: capabilities that the channel must satisfy
+ *
+ * Returns pointer to appropriate DMA channel on success or an error pointer.
+ */
+struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask)
+{
+	struct dma_chan *chan;
+
+	if (!mask)
+		return ERR_PTR(-ENODEV);
+
+	chan = __dma_request_channel(mask, NULL, NULL);
+	if (!chan)
+		chan = ERR_PTR(-ENODEV);
+
+	return chan;
+}
+EXPORT_SYMBOL_GPL(dma_request_chan_by_mask);
+
 void dma_release_channel(struct dma_chan *chan)
 {
 	mutex_lock(&dma_list_mutex);