On 09/12/11 16:50, Jassi Brar wrote:
> What do you think about ...
>
> diff --git a/arch/arm/common/pl330.c b/arch/arm/common/pl330.c
> index f407a6b..3a51cdd 100644
> --- a/arch/arm/common/pl330.c
> +++ b/arch/arm/common/pl330.c
> @@ -1546,7 +1546,7 @@ int pl330_chan_ctrl(void *ch_id, enum pl330_chan_op op)
>
> /* Start the next */
> case PL330_OP_START:
> - if (!_thrd_active(thrd) && !_start(thrd))
> + if (_state(thrd) == PL330_STATE_STOPPED && !_start(thrd))
Reintroduces the race condition, but you shorten the window:
* pl330_submit_req()
* pl330_chan_ctrl(PL330_OP_START)
* pl330_submit_req()
* pl330_chan_ctrl():spin_lock_irqsave()
* Transfer 1 finishes, interrupt raised (but pl330_update() is not
called as interrupts are disabled)
* _state(thrd) is PL330_STATE_STOPPED , _start() reissues the first
transaction.
* pl330_chan_ctrl():spin_lock_irqrestore()
* pl330_update() called for the first transaction, but it is running
again!
What about properly tracking what we have sent to the DMA? Something
like the following (warning *ugly* and untested code ahead, may eat your
kitten):
diff --git a/arch/arm/common/pl330.c b/arch/arm/common/pl330.c
index f407a6b..3652c4b 100644
--- a/arch/arm/common/pl330.c
+++ b/arch/arm/common/pl330.c
@@ -303,6 +303,7 @@ struct pl330_thread {
struct _pl330_req req[2];
/* Index of the last submitted request */
unsigned lstenq;
+ int req_running;
};
enum pl330_dmac_state {
@@ -836,31 +837,6 @@ static inline u32 _state(struct pl330_thread *thrd)
}
}
-/* If the request 'req' of thread 'thrd' is currently active */
-static inline bool _req_active(struct pl330_thread *thrd,
- struct _pl330_req *req)
-{
- void __iomem *regs = thrd->dmac->pinfo->base;
- u32 buf = req->mc_bus, pc = readl(regs + CPC(thrd->id));
-
- if (IS_FREE(req))
- return false;
-
- return (pc >= buf && pc <= buf + req->mc_len) ? true : false;
-}
-
-/* Returns 0 if the thread is inactive, ID of active req + 1 otherwise */
-static inline unsigned _thrd_active(struct pl330_thread *thrd)
-{
- if (_req_active(thrd, &thrd->req[0]))
- return 1; /* First req active */
-
- if (_req_active(thrd, &thrd->req[1]))
- return 2; /* Second req active */
-
- return 0;
-}
-
static void _stop(struct pl330_thread *thrd)
{
void __iomem *regs = thrd->dmac->pinfo->base;
@@ -897,11 +873,13 @@ static bool _trigger(struct pl330_thread *thrd)
if (_state(thrd) != PL330_STATE_STOPPED)
return true;
- if (!IS_FREE(&thrd->req[1 - thrd->lstenq]))
+ if (!IS_FREE(&thrd->req[1 - thrd->lstenq])) {
req = &thrd->req[1 - thrd->lstenq];
- else if (!IS_FREE(&thrd->req[thrd->lstenq]))
+ thrd->req_running = 2 - thrd->lstenq;
+ } else if (!IS_FREE(&thrd->req[thrd->lstenq])) {
req = &thrd->req[thrd->lstenq];
- else
+ thrd->req_running = 1 + thrd->lstenq;
+ } else
req = NULL;
/* Return if no request */
@@ -1384,6 +1362,7 @@ static void pl330_dotask(unsigned long data)
thrd->req[1].r = NULL;
MARK_FREE(&thrd->req[0]);
MARK_FREE(&thrd->req[1]);
+ thrd->req_running = 0;
/* Clear the reset flag */
pl330->dmac_tbd.reset_chan &= ~(1 << i);
@@ -1461,7 +1440,7 @@ int pl330_update(const struct pl330_info *pi)
thrd = &pl330->channels[id];
- active = _thrd_active(thrd);
+ active = thrd->req_running;
if (!active) /* Aborted */
continue;
@@ -1469,6 +1448,7 @@ int pl330_update(const struct pl330_info *pi)
rqdone = &thrd->req[active];
MARK_FREE(rqdone);
+ thrd->req_running = 0;
/* Get going again ASAP */
_start(thrd);
@@ -1527,10 +1507,11 @@ int pl330_chan_ctrl(void *ch_id, enum
pl330_chan_op op)
thrd->req[1].r = NULL;
MARK_FREE(&thrd->req[0]);
MARK_FREE(&thrd->req[1]);
+ thrd->req_running = 0;
break;
case PL330_OP_ABORT:
- active = _thrd_active(thrd);
+ active = thrd->req_running;
/* Make sure the channel is stopped */
_stop(thrd);
@@ -1543,10 +1524,11 @@ int pl330_chan_ctrl(void *ch_id, enum
pl330_chan_op op)
thrd->req[active].r = NULL;
MARK_FREE(&thrd->req[active]);
+ thrd->req_running = 0;
/* Start the next */
case PL330_OP_START:
- if (!_thrd_active(thrd) && !_start(thrd))
+ if (!thrd->req_running && !_start(thrd))
ret = -EIO;
break;
@@ -1587,7 +1569,7 @@ int pl330_chan_status(void *ch_id, struct
pl330_chanstatus *pstatus)
else
pstatus->faulting = false;
- active = _thrd_active(thrd);
+ active = thrd->req_running;
if (!active) {
/* Indicate that the thread is not running */
@@ -1662,6 +1644,7 @@ void *pl330_request_channel(const struct
pl330_info *pi)
MARK_FREE(&thrd->req[0]);
thrd->req[1].r = NULL;
MARK_FREE(&thrd->req[1]);
+ thrd->req_running = 0;
break;
}
}
@@ -1775,6 +1758,8 @@ static inline void _reset_thread(struct
pl330_thread *thrd)
+ pi->mcbufsz / 2;
thrd->req[1].r = NULL;
MARK_FREE(&thrd->req[1]);
+
+ thrd->req_running = 0;
}
static int dmac_alloc_threads(struct pl330_dmac *pl330)
> [Sorry I don't have any pl330 platform handy]
It's all right, I can do the testing. However, I'd like that somebody
with an exynos could test whatever patch we come up with in the end. I
don't want to break that platform again O:-)
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