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DMA: PL08x: fix infinite wait when terminating transfers 

If we try to pause a channel when terminating a transfer, we could end
up spinning for it to become inactive indefinitely, and can result in
an uninterruptible wait requiring a reset to recover from.

Terminating a transfer is supposed to take effect immediately, but may
result in data loss.

To make this clear, rename the function to pl08x_terminate_phy_chan().
Also, make sure it is always consistently called - with the spinlock
held and IRQs disabled, and ensure that the TC and ERR interrupt status
is always cleared.

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 2011-01-27 12:32:53 +00:00 committed by Dan Williams
parent d718f4ebdd
commit fb526210b2
1 changed files with 18 additions and 14 deletions
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32
drivers/dma/amba-pl08x.c
View File

@ -267,19 +267,24 @@ static void pl08x_resume_phy_chan(struct pl08x_phy_chan *ch)
}
/* Stops the channel */
static void pl08x_stop_phy_chan(struct pl08x_phy_chan *ch)
/*
* pl08x_terminate_phy_chan() stops the channel, clears the FIFO and
* clears any pending interrupt status. This should not be used for
* an on-going transfer, but as a method of shutting down a channel
* (eg, when it's no longer used) or terminating a transfer.
*/
static void pl08x_terminate_phy_chan(struct pl08x_driver_data *pl08x,
struct pl08x_phy_chan *ch)
{
u32 val;
u32 val = readl(ch->base + PL080_CH_CONFIG);
pl08x_pause_phy_chan(ch);
val &= ~(PL080_CONFIG_ENABLE | PL080_CONFIG_ERR_IRQ_MASK |
PL080_CONFIG_TC_IRQ_MASK);
/* Disable channel */
val = readl(ch->base + PL080_CH_CONFIG);
val &= ~PL080_CONFIG_ENABLE;
val &= ~PL080_CONFIG_ERR_IRQ_MASK;
val &= ~PL080_CONFIG_TC_IRQ_MASK;
writel(val, ch->base + PL080_CH_CONFIG);
writel(1 << ch->id, pl08x->base + PL080_ERR_CLEAR);
writel(1 << ch->id, pl08x->base + PL080_TC_CLEAR);
}
static inline u32 get_bytes_in_cctl(u32 cctl)
@ -404,13 +409,12 @@ static inline void pl08x_put_phy_channel(struct pl08x_driver_data *pl08x,
{
unsigned long flags;
spin_lock_irqsave(&ch->lock, flags);
/* Stop the channel and clear its interrupts */
pl08x_stop_phy_chan(ch);
writel((1 << ch->id), pl08x->base + PL080_ERR_CLEAR);
writel((1 << ch->id), pl08x->base + PL080_TC_CLEAR);
pl08x_terminate_phy_chan(pl08x, ch);
/* Mark it as free */
spin_lock_irqsave(&ch->lock, flags);
ch->serving = NULL;
spin_unlock_irqrestore(&ch->lock, flags);
}
@ -1449,7 +1453,7 @@ static int pl08x_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
plchan->state = PL08X_CHAN_IDLE;
if (plchan->phychan) {
pl08x_stop_phy_chan(plchan->phychan);
pl08x_terminate_phy_chan(pl08x, plchan->phychan);
/*
* Mark physical channel as free and free any slave