Hi,
More and more SoC have more than one DMA controller integrated.
If a device needs none slave DMA channel for operation (block copy from/to
memory mapped regions for example) at the moment when they request a channel it
is going to be taken from the first DMA controller which was registered, but
this might be not optimal for the device.
For example on AM654 we have two DMAs: main_udmap and mcu_udmap.
DDR to DDR memcpy is twice as fast on main_udmap compared to mcu_udmap, while
devices on MCU domain (OSPI for example) are more than twice as fast on
mcu_udmap than with main_udmap.
Because of probing order (mcu_udmap is probing first) modules would use
mcu_udmap instead of the better main_udmap. Currently the only solution is to
make a choice and disable the MEM_TO_MEM functionality on one of them which is
not a great solution.
With the introduction of DMA domain controllers we can utilize the best DMA
controller for the job around the SoC without the need to degrade performance.
If the dma-domain-controller is not present in DT or booted w/o DT the none
slave channel request will work as it does today.
The last patch introduces a new dma_domain_request_chan_by_mask() function and
I have a define for dma_request_chan_by_mask() to avoid breaking users of the
dma_request_chan_by_mask, but looking at the kernel we have small amount of
users:
drivers/gpu/drm/vc4/vc4_dsi.c
drivers/media/platform/omap/omap_vout_vrfb.c
drivers/media/platform/omap3isp/isphist.c
drivers/mtd/spi-nor/cadence-quadspi.c
drivers/spi/spi-ti-qspi.c
If it is acceptable we can modify the parameters of dma_request_chan_by_mask()
to include ther device pointer and at the same time change all of the clients
by giving NULL or in case of the last two their dev.
Regards,
Peter
---
Peter Ujfalusi (3):
dt-bindings: dma: Add documentation for DMA domains
dmaengine: of_dma: Function to look up the DMA domain of a client
dmaengine: Support for requesting channels preferring DMA domain
controller
.../devicetree/bindings/dma/dma-domain.yaml | 59 +++++++++++++++++++
drivers/dma/dmaengine.c | 17 ++++--
drivers/dma/of-dma.c | 42 +++++++++++++
include/linux/dmaengine.h | 9 ++-
include/linux/of_dma.h | 7 +++
5 files changed, 126 insertions(+), 8 deletions(-)
create mode 100644 Documentation/devicetree/bindings/dma/dma-domain.yaml
--
Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
Find the DMA domain controller of the client device by iterating up in
device tree looking for the closest 'dma-domain-controller' property.
If the client's node is not provided then check the DT root for the
controller.
Signed-off-by: Peter Ujfalusi <[email protected]>
---
drivers/dma/of-dma.c | 42 ++++++++++++++++++++++++++++++++++++++++++
include/linux/of_dma.h | 7 +++++++
2 files changed, 49 insertions(+)
diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
index c2d779daa4b5..04b5795cd76b 100644
--- a/drivers/dma/of-dma.c
+++ b/drivers/dma/of-dma.c
@@ -18,6 +18,48 @@
static LIST_HEAD(of_dma_list);
static DEFINE_MUTEX(of_dma_lock);
+/**
+ * of_find_dma_domain - Get the domain DMA controller
+ * @np: device node of the client device
+ *
+ * Look up the DMA controller of the domain the client device is part of.
+ * Finds the dma-domain controller the client device belongs to. It is used when
+ * requesting non slave channels (like channel for memcpy) to make sure that the
+ * channel can be request from a DMA controller which can service the given
+ * domain best.
+ *
+ * Returns the device_node pointer of the DMA controller or succes or NULL on
+ * error.
+ */
+struct device_node *of_find_dma_domain(struct device_node *np)
+{
+ struct device_node *dma_domain = NULL;
+ phandle dma_phandle;
+
+ /*
+ * If no device_node is provided look at the root level for system
+ * default DMA controller for modules.
+ */
+ if (!np)
+ np = of_root;
+
+ if (!np || !of_node_get(np))
+ return NULL;
+
+ do {
+ if (of_property_read_u32(np, "dma-domain-controller",
+ &dma_phandle))
+ np = of_get_next_parent(np);
+ else {
+ dma_domain = of_find_node_by_phandle(dma_phandle);
+ of_node_put(np);
+ }
+ } while (!dma_domain && np);
+
+ return dma_domain;
+}
+EXPORT_SYMBOL_GPL(of_find_dma_domain);
+
/**
* of_dma_find_controller - Get a DMA controller in DT DMA helpers list
* @dma_spec: pointer to DMA specifier as found in the device tree
diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
index fd706cdf255c..6eab0a8d3335 100644
--- a/include/linux/of_dma.h
+++ b/include/linux/of_dma.h
@@ -32,6 +32,8 @@ struct of_dma_filter_info {
};
#ifdef CONFIG_DMA_OF
+extern struct device_node *of_find_dma_domain(struct device_node *np);
+
extern int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
@@ -52,6 +54,11 @@ extern struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec
struct of_dma *ofdma);
#else
+static inline struct device_node *of_find_dma_domain(struct device_node *np)
+{
+ return NULL;
+}
+
static inline int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
--
Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
In case the channel is not requested via the slave API, use the
of_find_dma_domain() to see if a system default DMA controller is
specified.
Add new function which can be used by clients to request channels by mask
from their DMA domain controller if specified.
Client drivers can take advantage of the domain support by moving from
dma_request_chan_by_mask() to dma_domain_request_chan_by_mask()
Signed-off-by: Peter Ujfalusi <[email protected]>
---
drivers/dma/dmaengine.c | 17 ++++++++++++-----
include/linux/dmaengine.h | 9 ++++++---
2 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 6baddf7dcbfd..087450eed68c 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -640,6 +640,10 @@ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
struct dma_device *device, *_d;
struct dma_chan *chan = NULL;
+ /* If np is not specified, get the default DMA domain controller */
+ if (!np)
+ np = of_find_dma_domain(NULL);
+
/* Find a channel */
mutex_lock(&dma_list_mutex);
list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
@@ -751,19 +755,22 @@ struct dma_chan *dma_request_slave_channel(struct device *dev,
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
+ * dma_domain_request_chan_by_mask - allocate a channel by mask from DMA domain
+ * @dev: pointer to client device structure
+ * @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 *dma_domain_request_chan_by_mask(struct device *dev,
+ const dma_cap_mask_t *mask)
{
struct dma_chan *chan;
if (!mask)
return ERR_PTR(-ENODEV);
- chan = __dma_request_channel(mask, NULL, NULL, NULL);
+ chan = __dma_request_channel(mask, NULL, NULL,
+ of_find_dma_domain(dev->of_node));
if (!chan) {
mutex_lock(&dma_list_mutex);
if (list_empty(&dma_device_list))
@@ -775,7 +782,7 @@ struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask)
return chan;
}
-EXPORT_SYMBOL_GPL(dma_request_chan_by_mask);
+EXPORT_SYMBOL_GPL(dma_domain_request_chan_by_mask);
void dma_release_channel(struct dma_chan *chan)
{
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 3b2e8e302f6c..9f94df81e83f 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -1438,7 +1438,8 @@ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
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);
-struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask);
+struct dma_chan *dma_domain_request_chan_by_mask(struct device *dev,
+ 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);
@@ -1475,8 +1476,8 @@ static inline struct dma_chan *dma_request_chan(struct device *dev,
{
return ERR_PTR(-ENODEV);
}
-static inline struct dma_chan *dma_request_chan_by_mask(
- const dma_cap_mask_t *mask)
+static inline struct dma_chan *dma_domain_request_chan_by_mask(struct device *dev,
+ const dma_cap_mask_t *mask)
{
return ERR_PTR(-ENODEV);
}
@@ -1537,6 +1538,8 @@ struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
__dma_request_channel(&(mask), x, y, NULL)
#define dma_request_slave_channel_compat(mask, x, y, dev, name) \
__dma_request_slave_channel_compat(&(mask), x, y, dev, name)
+#define dma_request_chan_by_mask(mask) \
+ dma_domain_request_chan_by_mask(NULL, mask)
static inline struct dma_chan
*__dma_request_slave_channel_compat(const dma_cap_mask_t *mask,
--
Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki