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Date: Tue, 26 Nov 2013 12:40:51 -0700
From: Stephen Warren <swarren@...dotorg.org>
To: Dan Williams <dan.j.williams@...el.com>,
Vinod Koul <vinod.koul@...el.com>
Cc: dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
Stephen Warren <swarren@...dia.com>,
Lars-Peter Clausen <lars@...afoo.de>
Subject: [PATCH V4] dma: add dma_get_any_slave_channel(), for use in of_xlate()
From: Stephen Warren <swarren@...dia.com>
mmp_pdma.c implements a custom of_xlate() function that is 95% identical
to what Tegra will need. Create a function to implement the common part,
so everyone doesn't just cut/paste the implementation.
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Vinod Koul <vinod.koul@...el.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>
Cc: dmaengine@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Stephen Warren <swarren@...dia.com>
---
v3:
* Re-implemented the common code as dma_get_any_slave_channel(), in
dmaengine.c. This allows it to mutex_lock(&dma_list_mutex), and hence
avoid the retry loop.
* Rather than having the common code call out to a driver-provided
callback at the tail (which avoided drivers having to implement an
of_xlate function themselves), have drivers implement a custom
of_xlate() again, which mostly just calls the new
dma_get_any_slave_channel(), then does any extra custom work.
v2:
* Squashed the conversion of mmp_pdma.c into the patch that added the
common implementation, so it's easier to see the whole conversion in
one go.
This patch is a dependency for a series that reworks many of the Tegra
drivers.
As such, it needs to go into a topic branch on its own, based directly
on 3.13-rc1. If the DMA maintainers ack the patches I'm happy to create
this topic branch myself and send a pull request to the DMA tree. Or the
patches can be applied to a topic branch by the DMA maintainers and I
will merge their topic branch into the Tegra rework branch that I
mentioned.
Note that this patch is independant from the "dma: add channel request
API that supports deferred probe" which I just sent, so it could
(should?) be a different topic branch.
---
drivers/dma/dmaengine.c | 28 ++++++++++++++++++++++++++++
drivers/dma/mmp_pdma.c | 30 +++++++-----------------------
include/linux/dmaengine.h | 1 +
3 files changed, 36 insertions(+), 23 deletions(-)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index e17e9b22d85e..24095ff8a93b 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -535,6 +535,34 @@ struct dma_chan *dma_get_slave_channel(struct dma_chan *chan)
}
EXPORT_SYMBOL_GPL(dma_get_slave_channel);
+struct dma_chan *dma_get_any_slave_channel(struct dma_device *device)
+{
+ dma_cap_mask_t mask;
+ struct dma_chan *chan;
+ int err;
+
+ dma_cap_zero(mask);
+ dma_cap_set(DMA_SLAVE, mask);
+
+ /* lock against __dma_request_channel */
+ mutex_lock(&dma_list_mutex);
+
+ chan = private_candidate(&mask, device, NULL, NULL);
+ if (chan) {
+ err = dma_chan_get(chan);
+ if (err) {
+ pr_debug("%s: failed to get %s: (%d)\n",
+ __func__, dma_chan_name(chan), err);
+ chan = NULL;
+ }
+ }
+
+ mutex_unlock(&dma_list_mutex);
+
+ return chan;
+}
+EXPORT_SYMBOL_GPL(dma_get_any_slave_channel);
+
/**
* __dma_request_channel - try to allocate an exclusive channel
* @mask: capabilities that the channel must satisfy
diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c
index dcb1e05149a7..2998f1bffac1 100644
--- a/drivers/dma/mmp_pdma.c
+++ b/drivers/dma/mmp_pdma.c
@@ -893,33 +893,17 @@ static struct dma_chan *mmp_pdma_dma_xlate(struct of_phandle_args *dma_spec,
struct of_dma *ofdma)
{
struct mmp_pdma_device *d = ofdma->of_dma_data;
- struct dma_chan *chan, *candidate;
+ struct dma_chan *chan;
+ struct mmp_pdma_chan *c;
-retry:
- candidate = NULL;
-
- /* walk the list of channels registered with the current instance and
- * find one that is currently unused */
- list_for_each_entry(chan, &d->device.channels, device_node)
- if (chan->client_count == 0) {
- candidate = chan;
- break;
- }
-
- if (!candidate)
+ chan = dma_get_any_slave_channel(&d->device);
+ if (!chan)
return NULL;
- /* dma_get_slave_channel will return NULL if we lost a race between
- * the lookup and the reservation */
- chan = dma_get_slave_channel(candidate);
-
- if (chan) {
- struct mmp_pdma_chan *c = to_mmp_pdma_chan(chan);
- c->drcmr = dma_spec->args[0];
- return chan;
- }
+ c = to_mmp_pdma_chan(chan);
+ c->drcmr = dma_spec->args[0];
- goto retry;
+ return chan;
}
static int mmp_pdma_probe(struct platform_device *op)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index ed92b30a02fd..bae1568416f8 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -1087,6 +1087,7 @@ 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_get_slave_channel(struct dma_chan *chan);
+struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
struct dma_chan *net_dma_find_channel(void);
#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
#define dma_request_slave_channel_compat(mask, x, y, dev, name) \
--
1.8.1.5
--
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