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,
const dma_cap_mask_t *mask);
To request a slave channel. The mask parameter is optional and it is used
to check if the received channel's capabilities can satisfy the requested
mask. 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 RESOURCE_DMA from the requester's device.
This legacy mode needs changes in platform code, in dmaengine drivers and
finally the dmaengine user drivers can be converted:
RESOURCE_DMA needs to be added to the platform devices with names
For each dmaengine driver a string array listing the devices handled by the
given DMA driver:
static char *da8xx_edma0_devices[] = {
"davinci-mcasp.0",
"da830-mmc.0",
};
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.devnames = da8xx_edma0_devices;
da8xx_edma0_pdata.devcnt = ARRAY_SIZE(da8xx_edma0_devices);
The DMA driver then needs to convigure the needed device -> filter_fn
mapping before it registers with dma_async_device_register() :
if (info->devnames) {
ecc->dma_slave.filter_map.devnames = info->devnames;
ecc->dma_slave.filter_map.devcnt = info->devcnt;
ecc->dma_slave.filter_map.filter_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 requests the named DMA resource
using the requester's pdev and with the needed information available it
will try to get the channele with the dma_get_channel() internal function.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
---
drivers/dma/dmaengine.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/dmaengine.h | 21 +++++++++++
2 files changed, 112 insertions(+)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 1249165fb4b2..14c8e8a76641 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>
@@ -715,6 +716,96 @@ struct dma_chan *dma_request_slave_channel(struct device *dev,
}
EXPORT_SYMBOL_GPL(dma_request_slave_channel);
+static bool dma_filter_dev_is_match(struct dma_device *device,
+ struct device *dev)
+{
+ bool found = false;
+ int i;
+
+ if (!device->filter_map.devcnt)
+ return false;
+
+ for (i = 0; i < device->filter_map.devcnt; i++) {
+ if (!strcmp(device->filter_map.devnames[i], dev_name(dev))) {
+ found = true;
+ break;
+ }
+ }
+
+ return found;
+}
+
+struct dma_chan *dma_request_chan(struct device *dev, const char *name,
+ const dma_cap_mask_t *mask)
+{
+ struct dma_device *device, *_d;
+ struct dma_chan *chan = NULL;
+
+ /* If device-tree is present get slave info from here */
+ if (dev->of_node)
+ 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) && !chan)
+ chan = acpi_dma_request_slave_chan_by_name(dev, name);
+
+ if (chan)
+ goto validate;
+
+ /* Try to find the channel via the DMA filter map(s) */
+ mutex_lock(&dma_list_mutex);
+ list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
+ bool match = dma_filter_dev_is_match(device, dev);
+ struct resource *r;
+
+ if (!match)
+ continue;
+
+ r = platform_get_resource_byname(to_platform_device(dev),
+ IORESOURCE_DMA, name);
+ if (!r)
+ continue;
+
+ chan = dma_get_channel(device, mask,
+ device->filter_map.filter_fn,
+ &r->start);
+ if (!IS_ERR(chan))
+ break;
+ }
+ mutex_unlock(&dma_list_mutex);
+
+ if (!chan)
+ return ERR_PTR(-EPROBE_DEFER);
+validate:
+ if (IS_ERR(chan) || !mask)
+ return chan;
+
+ if (!__dma_device_satisfies_mask(chan->device, mask)) {
+ dev_dbg(chan->device->dev, "%s: wrong capabilities for %s:%s\n",
+ __func__, dev_name(dev), name);
+ dma_release_channel(chan);
+ chan = ERR_PTR(-ENODEV);
+ }
+
+ return chan;
+}
+EXPORT_SYMBOL_GPL(dma_request_chan);
+
+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);
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index a2b7c2071cf4..e17be9a136f1 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -606,6 +606,12 @@ enum dmaengine_alignment {
DMAENGINE_ALIGN_64_BYTES = 6,
};
+struct dma_filter {
+ dma_filter_fn filter_fn;
+ int devcnt;
+ char **devnames;
+};
+
/**
* struct dma_device - info on the entity supplying DMA services
* @chancnt: how many DMA channels are supported
@@ -669,6 +675,7 @@ struct dma_device {
unsigned int privatecnt;
struct list_head channels;
struct list_head global_node;
+ struct dma_filter filter_map;
dma_cap_mask_t cap_mask;
unsigned short max_xor;
unsigned short max_pq;
@@ -1235,6 +1242,11 @@ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
struct dma_chan *dma_request_slave_channel_reason(struct device *dev,
const char *name);
struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name);
+
+struct dma_chan *dma_request_chan(struct device *dev, const char *name,
+ const dma_cap_mask_t *mask);
+struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask);
+
void dma_release_channel(struct dma_chan *chan);
int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps);
#else
@@ -1268,6 +1280,15 @@ static inline struct dma_chan *dma_request_slave_channel(struct device *dev,
{
return NULL;
}
+static inline struct dma_chan *dma_request_chan(struct device *dev,
+ const char *name, const dma_cap_mask_t *mask)
+{
+ return ERR_PTR(-ENODEV);
+}
+static inline struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask)
+{
+ return ERR_PTR(-ENODEV);
+}
static inline void dma_release_channel(struct dma_chan *chan)
{
}
--
2.6.3
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