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ARM: PL08x: fix atomic_t usage and tx_submit() return value range

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The last_issued variable uses an atomic type, which is only
incremented inside a protected region, and then read.  Everywhere else
only reads the value, so it isn't using atomic_t correctly, and it
doesn't even need to.  Moreover, the DMA engine code provides us with
a variable for this already - chan.cookie.  Use chan.cookie instead.

Also, avoid negative dma_cookie_t values - negative returns from
tx_submit() mean failure, yet in reality we always succeed.  Restart
from cookie 1, just like other DMA engine drivers do.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Russell King - ARM Linux 2011-01-03 22:31:04 +00:00 committed by Dan Williams
parent 4440aacf3a
commit 91aa5fadb8
2 changed files with 9 additions and 10 deletions
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18
drivers/dma/amba-pl08x.c
View File

@ -74,7 +74,6 @@
#include <asm/hardware/pl080.h>
#include <asm/dma.h>
#include <asm/mach/dma.h>
#include <asm/atomic.h>
#include <asm/processor.h>
#include <asm/cacheflush.h>
@ -1082,8 +1081,10 @@ static dma_cookie_t pl08x_tx_submit(struct dma_async_tx_descriptor *tx)
{
struct pl08x_dma_chan *plchan = to_pl08x_chan(tx->chan);
atomic_inc(&plchan->last_issued);
tx->cookie = atomic_read(&plchan->last_issued);
plchan->chan.cookie += 1;
if (plchan->chan.cookie < 0)
plchan->chan.cookie = 1;
tx->cookie = plchan->chan.cookie;
/* This unlock follows the lock in the prep() function */
spin_unlock_irqrestore(&plchan->lock, plchan->lockflags);
@ -1115,7 +1116,7 @@ pl08x_dma_tx_status(struct dma_chan *chan,
enum dma_status ret;
u32 bytesleft = 0;
last_used = atomic_read(&plchan->last_issued);
last_used = plchan->chan.cookie;
last_complete = plchan->lc;
ret = dma_async_is_complete(cookie, last_complete, last_used);
@ -1131,7 +1132,7 @@ pl08x_dma_tx_status(struct dma_chan *chan,
/*
* This cookie not complete yet
*/
last_used = atomic_read(&plchan->last_issued);
last_used = plchan->chan.cookie;
last_complete = plchan->lc;
/* Get number of bytes left in the active transactions and queue */
@ -1641,8 +1642,7 @@ static void pl08x_tasklet(unsigned long data)
/*
* Update last completed
*/
plchan->lc =
(plchan->at->tx.cookie);
plchan->lc = plchan->at->tx.cookie;
/*
* Callback to signal completion
@ -1820,8 +1820,8 @@ static int pl08x_dma_init_virtual_channels(struct pl08x_driver_data *pl08x,
chan->name);
chan->chan.device = dmadev;
atomic_set(&chan->last_issued, 0);
chan->lc = atomic_read(&chan->last_issued);
chan->chan.cookie = 0;
chan->lc = 0;
spin_lock_init(&chan->lock);
INIT_LIST_HEAD(&chan->desc_list);

1
include/linux/amba/pl08x.h
View File

@ -174,7 +174,6 @@ struct pl08x_dma_chan {
struct pl08x_channel_data *cd;
dma_addr_t runtime_addr;
enum dma_data_direction runtime_direction;
atomic_t last_issued;
dma_cookie_t lc;
struct list_head desc_list;
struct pl08x_txd *at;