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Subject[PATCH v1 4/8] dmaengine: use atomic_t for struct dma_chan->client_count field
Date
Use atomic_t for struct dma_chan->client_count field to prepare for
DMA device hotplug.

Signed-off-by: Jiang Liu <liuj97@gmail.com>
---
drivers/dma/dmaengine.c | 41 ++++++++++++++++++++++++++---------------
include/linux/dmaengine.h | 4 ++++
2 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 198d891..da7a683 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -62,6 +62,18 @@
#include <linux/idr.h>
#include <linux/slab.h>

+#ifndef CONFIG_DMA_ENGINE_HOTPLUG
+#define dma_chan_ref_read(chan) ((chan)->client_count)
+#define dma_chan_ref_set(chan, v) ((chan)->client_count = (v))
+#define dma_chan_ref_inc(chan) ((chan)->client_count++)
+#define dma_chan_ref_dec_and_test(ch) (--(chan)->client_count == 0)
+#else /* CONFIG_DMA_ENGINE_HOTPLUG */
+#define dma_chan_ref_read(chan) atomic_read(&(chan)->client_count)
+#define dma_chan_ref_set(chan, v) atomic_set(&(chan)->client_count, (v))
+#define dma_chan_ref_inc(chan) atomic_inc(&(chan)->client_count)
+#define dma_chan_ref_dec_and_test(ch) atomic_dec_and_test(&(ch)->client_count)
+#endif /* CONFIG_DMA_ENGINE_HOTPLUG */
+
static DEFINE_MUTEX(dma_list_mutex);
static DEFINE_IDR(dma_idr);
static LIST_HEAD(dma_device_list);
@@ -132,7 +144,7 @@ static ssize_t show_in_use(struct device *dev, struct device_attribute *attr, ch
mutex_lock(&dma_list_mutex);
chan = dev_to_dma_chan(dev);
if (chan)
- err = sprintf(buf, "%d\n", chan->client_count);
+ err = sprintf(buf, "%d\n", dma_chan_ref_read(chan));
else
err = -ENODEV;
mutex_unlock(&dma_list_mutex);
@@ -201,15 +213,15 @@ static int dma_chan_get(struct dma_chan *chan)
if (!try_module_get(owner))
return -ENODEV;

- chan->client_count++;
+ dma_chan_ref_inc(chan);

/* allocate upon first client reference */
- if (chan->client_count == 1) {
+ if (dma_chan_ref_read(chan) == 1) {
int desc_cnt = chan->device->device_alloc_chan_resources(chan);

if (desc_cnt < 0) {
err = desc_cnt;
- chan->client_count = 0;
+ dma_chan_ref_set(chan, 0);
module_put(owner);
}
}
@@ -225,9 +237,8 @@ static int dma_chan_get(struct dma_chan *chan)
*/
static void dma_chan_put(struct dma_chan *chan)
{
- BUG_ON(chan->client_count <= 0);
- chan->client_count--;
- if (chan->client_count == 0)
+ BUG_ON(dma_chan_ref_read(chan) <= 0);
+ if (dma_chan_ref_dec_and_test(chan))
chan->device->device_free_chan_resources(chan);
module_put(dma_chan_to_owner(chan));
}
@@ -341,7 +352,7 @@ void dma_issue_pending_all(void)
if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
continue;
list_for_each_entry(chan, &device->channels, device_node)
- if (chan->client_count)
+ if (dma_chan_ref_read(chan))
device->device_issue_pending(chan);
}
rcu_read_unlock();
@@ -460,12 +471,12 @@ static struct dma_chan *private_candidate(dma_cap_mask_t *mask, struct dma_devic
if (dev->chancnt > 1 && !dma_has_cap(DMA_PRIVATE, dev->cap_mask))
list_for_each_entry(chan, &dev->channels, device_node) {
/* some channels are already publicly allocated */
- if (chan->client_count)
+ if (dma_chan_ref_read(chan))
return NULL;
}

list_for_each_entry(chan, &dev->channels, device_node) {
- if (chan->client_count) {
+ if (dma_chan_ref_read(chan)) {
pr_debug("%s: %s busy\n",
__func__, dma_chan_name(chan));
continue;
@@ -530,8 +541,8 @@ EXPORT_SYMBOL_GPL(__dma_request_channel);
void dma_release_channel(struct dma_chan *chan)
{
mutex_lock(&dma_list_mutex);
- WARN_ONCE(chan->client_count != 1,
- "chan reference count %d != 1\n", chan->client_count);
+ WARN_ONCE(dma_chan_ref_read(chan) != 1,
+ "chan reference count %d != 1\n", dma_chan_ref_read(chan));
dma_chan_put(chan);
/* drop PRIVATE cap enabled by __dma_request_channel() */
if (--chan->device->privatecnt == 0)
@@ -722,7 +733,7 @@ int dma_async_device_register(struct dma_device *device)
atomic_dec(idr_ref);
goto err_out;
}
- chan->client_count = 0;
+ dma_chan_ref_set(chan, 0);
}
device->chancnt = chancnt;

@@ -784,9 +795,9 @@ void dma_async_device_unregister(struct dma_device *device)
}

list_for_each_entry(chan, &device->channels, device_node) {
- WARN_ONCE(chan->client_count,
+ WARN_ONCE(dma_chan_ref_read(chan),
"%s called while %d clients hold a reference\n",
- __func__, chan->client_count);
+ __func__, dma_chan_ref_read(chan));
mutex_lock(&dma_list_mutex);
chan->dev->chan = NULL;
mutex_unlock(&dma_list_mutex);
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index f9a2e5e..d1532dc 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -279,7 +279,11 @@ struct dma_chan {

struct list_head device_node;
struct dma_chan_percpu __percpu *local;
+#ifdef CONFIG_DMA_ENGINE_HOTPLUG
+ atomic_t client_count;
+#else
int client_count;
+#endif
int table_count;
void *private;
};
--
1.7.5.4


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