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async_tx: trim dma_async_tx_descriptor in 'no channel switch' case
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Saves 24 bytes per descriptor (64-bit) when the channel-switching
capabilities of async_tx are not required.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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@djbw
djbw committed May 17, 2010
1 parent c86e140 commit caa20d9
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Showing 3 changed files with 88 additions and 34 deletions.
46 changes: 19 additions & 27 deletions crypto/async_tx/async_tx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -81,18 +81,13 @@ async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
struct dma_device *device = chan->device;
struct dma_async_tx_descriptor *intr_tx = (void *) ~0;

#ifdef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
BUG();
#endif

/* first check to see if we can still append to depend_tx */
spin_lock_bh(&depend_tx->lock);
if (depend_tx->parent && depend_tx->chan == tx->chan) {
tx->parent = depend_tx;
depend_tx->next = tx;
txd_lock(depend_tx);
if (txd_parent(depend_tx) && depend_tx->chan == tx->chan) {
txd_chain(depend_tx, tx);
intr_tx = NULL;
}
spin_unlock_bh(&depend_tx->lock);
txd_unlock(depend_tx);

/* attached dependency, flush the parent channel */
if (!intr_tx) {
Expand All @@ -111,24 +106,22 @@ async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
if (intr_tx) {
intr_tx->callback = NULL;
intr_tx->callback_param = NULL;
tx->parent = intr_tx;
/* safe to set ->next outside the lock since we know we are
/* safe to chain outside the lock since we know we are
* not submitted yet
*/
intr_tx->next = tx;
txd_chain(intr_tx, tx);

/* check if we need to append */
spin_lock_bh(&depend_tx->lock);
if (depend_tx->parent) {
intr_tx->parent = depend_tx;
depend_tx->next = intr_tx;
txd_lock(depend_tx);
if (txd_parent(depend_tx)) {
txd_chain(depend_tx, intr_tx);
async_tx_ack(intr_tx);
intr_tx = NULL;
}
spin_unlock_bh(&depend_tx->lock);
txd_unlock(depend_tx);

if (intr_tx) {
intr_tx->parent = NULL;
txd_clear_parent(intr_tx);
intr_tx->tx_submit(intr_tx);
async_tx_ack(intr_tx);
}
Expand Down Expand Up @@ -176,21 +169,20 @@ async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
* 2/ dependencies are 1:1 i.e. two transactions can
* not depend on the same parent
*/
BUG_ON(async_tx_test_ack(depend_tx) || depend_tx->next ||
tx->parent);
BUG_ON(async_tx_test_ack(depend_tx) || txd_next(depend_tx) ||
txd_parent(tx));

/* the lock prevents async_tx_run_dependencies from missing
* the setting of ->next when ->parent != NULL
*/
spin_lock_bh(&depend_tx->lock);
if (depend_tx->parent) {
txd_lock(depend_tx);
if (txd_parent(depend_tx)) {
/* we have a parent so we can not submit directly
* if we are staying on the same channel: append
* else: channel switch
*/
if (depend_tx->chan == chan) {
tx->parent = depend_tx;
depend_tx->next = tx;
txd_chain(depend_tx, tx);
s = ASYNC_TX_SUBMITTED;
} else
s = ASYNC_TX_CHANNEL_SWITCH;
Expand All @@ -203,7 +195,7 @@ async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
else
s = ASYNC_TX_CHANNEL_SWITCH;
}
spin_unlock_bh(&depend_tx->lock);
txd_unlock(depend_tx);

switch (s) {
case ASYNC_TX_SUBMITTED:
Expand All @@ -212,12 +204,12 @@ async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
async_tx_channel_switch(depend_tx, tx);
break;
case ASYNC_TX_DIRECT_SUBMIT:
tx->parent = NULL;
txd_clear_parent(tx);
tx->tx_submit(tx);
break;
}
} else {
tx->parent = NULL;
txd_clear_parent(tx);
tx->tx_submit(tx);
}

Expand Down
16 changes: 9 additions & 7 deletions drivers/dma/dmaengine.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -978,7 +978,9 @@ void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
struct dma_chan *chan)
{
tx->chan = chan;
#ifndef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
spin_lock_init(&tx->lock);
#endif
}
EXPORT_SYMBOL(dma_async_tx_descriptor_init);

Expand Down Expand Up @@ -1011,30 +1013,30 @@ EXPORT_SYMBOL_GPL(dma_wait_for_async_tx);
*/
void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
{
struct dma_async_tx_descriptor *dep = tx->next;
struct dma_async_tx_descriptor *dep = txd_next(tx);
struct dma_async_tx_descriptor *dep_next;
struct dma_chan *chan;

if (!dep)
return;

/* we'll submit tx->next now, so clear the link */
tx->next = NULL;
txd_clear_next(tx);
chan = dep->chan;

/* keep submitting up until a channel switch is detected
* in that case we will be called again as a result of
* processing the interrupt from async_tx_channel_switch
*/
for (; dep; dep = dep_next) {
spin_lock_bh(&dep->lock);
dep->parent = NULL;
dep_next = dep->next;
txd_lock(dep);
txd_clear_parent(dep);
dep_next = txd_next(dep);
if (dep_next && dep_next->chan == chan)
dep->next = NULL; /* ->next will be submitted */
txd_clear_next(dep); /* ->next will be submitted */
else
dep_next = NULL; /* submit current dep and terminate */
spin_unlock_bh(&dep->lock);
txd_unlock(dep);

dep->tx_submit(dep);
}
Expand Down
60 changes: 60 additions & 0 deletions include/linux/dmaengine.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -230,11 +230,71 @@ struct dma_async_tx_descriptor {
dma_cookie_t (*tx_submit)(struct dma_async_tx_descriptor *tx);
dma_async_tx_callback callback;
void *callback_param;
#ifndef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
struct dma_async_tx_descriptor *next;
struct dma_async_tx_descriptor *parent;
spinlock_t lock;
#endif
};

#ifdef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
static inline void txd_lock(struct dma_async_tx_descriptor *txd)
{
}
static inline void txd_unlock(struct dma_async_tx_descriptor *txd)
{
}
static inline void txd_chain(struct dma_async_tx_descriptor *txd, struct dma_async_tx_descriptor *next)
{
BUG();
}
static inline void txd_clear_parent(struct dma_async_tx_descriptor *txd)
{
}
static inline void txd_clear_next(struct dma_async_tx_descriptor *txd)
{
}
static inline struct dma_async_tx_descriptor *txd_next(struct dma_async_tx_descriptor *txd)
{
return NULL;
}
static inline struct dma_async_tx_descriptor *txd_parent(struct dma_async_tx_descriptor *txd)
{
return NULL;
}

#else
static inline void txd_lock(struct dma_async_tx_descriptor *txd)
{
spin_lock_bh(&txd->lock);
}
static inline void txd_unlock(struct dma_async_tx_descriptor *txd)
{
spin_unlock_bh(&txd->lock);
}
static inline void txd_chain(struct dma_async_tx_descriptor *txd, struct dma_async_tx_descriptor *next)
{
txd->next = next;
next->parent = txd;
}
static inline void txd_clear_parent(struct dma_async_tx_descriptor *txd)
{
txd->parent = NULL;
}
static inline void txd_clear_next(struct dma_async_tx_descriptor *txd)
{
txd->next = NULL;
}
static inline struct dma_async_tx_descriptor *txd_parent(struct dma_async_tx_descriptor *txd)
{
return txd->parent;
}
static inline struct dma_async_tx_descriptor *txd_next(struct dma_async_tx_descriptor *txd)
{
return txd->next;
}
#endif

/**
* struct dma_device - info on the entity supplying DMA services
* @chancnt: how many DMA channels are supported
Expand Down

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