Commit 91aa5fad authored by Russell King - ARM Linux's avatar Russell King - ARM Linux Committed by Dan Williams
Browse files

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



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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
Acked-by: default avatarLinus Walleij <linus.walleij@stericsson.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 4440aacf

drivers/dma/amba-pl08x.c

+9 −9
Original line number Diff line number Diff line
@@ -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);

include/linux/amba/pl08x.h

+0 −1
Original line number Diff line number Diff line
@@ -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;