On Tue, Mar 31, 2015 at 9:10 AM, Scott Branden <sbran...@broadcom.com> wrote:
> Hi Vinod, Jassi,
>
> Some details on the problem encountered.
>
>
> On 15-03-30 10:25 AM, Vinod Koul wrote:
>>
>> On Mon, Mar 30, 2015 at 10:17:17PM +0530, Jassi Brar wrote:
>>>
>>> On Fri, Mar 27, 2015 at 5:25 AM, Scott Branden <sbran...@broadcom.com>
>>> wrote:
>>>>
>>>> From: ismail <ism...@broadcom.com>
>>>>
>>>> Update the thread running index before issuing the
>>>> GO command to the DMAC.
>>>>
>>>> Tested-by: Mohamed Ismail Abdul Packir Mohamed <ism...@broadcom.com>
>>>> Reviewed-by: Ray Jui <r...@broadcom.com>
>>>> Reviewed-by: Arun Parameswaran <apara...@broadcom.com>
>>>> Reviewed-by: Scott Branden <sbran...@broadcom.com>
>>>> Signed-off-by: Scott Branden <sbran...@broadcom.com>
>>>> Signed-off-by: Mohamed Ismail Abdul Packir Mohamed <ism...@broadcom.com>
>>>> ---
>>>> drivers/dma/pl330.c | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
>>>> index 0e1f567..631642d 100644
>>>> --- a/drivers/dma/pl330.c
>>>> +++ b/drivers/dma/pl330.c
>>>> @@ -1072,11 +1072,11 @@ static bool _trigger(struct pl330_thread *thrd)
>>>> /* Set to generate interrupts for SEV */
>>>> writel(readl(regs + INTEN) | (1 << thrd->ev), regs + INTEN);
>>>>
>>>> + thrd->req_running = idx;
>>>> +
>>>> /* Only manager can execute GO */
>>>> _execute_DBGINSN(thrd, insn, true);
>>>>
>>>> - thrd->req_running = idx;
>>>> -
>>>
>>> It would help to know what the behavior looks like before and after
>>> the patch. If anything we should look at locking rather the
>>> reordering.
>>
>> Yes that ia fair request, looking at changelog it is hard to understand
>> the
>> issue seen?
>>
> We encountered this problem as we modified the driver to make SMC calls to a
> TZ handler. This slowed down the driver to the point where DMA transactions
> easily failed. I believe the same could be accomplished by adding a delay
> between the GOCMD and update of the req_running and running the built in
> dmatest.
>
> The DMA transaction is broken if the interrupt occurs before the
> thrd->req_running is updated.
>
> The pl330 issues a GOCMD (in _trigger function) to start a new transfer.
>
> The issue of GOCMD generates an interrupt and the IRQ handler will call the
> pl330_update function to process the interrupt.
>
> The pl330_update function will verify the thread running index and break the
> transaction, if the thread running index is not set.
>
As I suspected the locking seems screwed up. The following patch
should fix the race properly. Can you please test the attached patches
instead?
Thanks.
From 1c44fc936d05fef3259354da1574c536ed1691c7 Mon Sep 17 00:00:00 2001
From: Jassi Brar <jaswinder.si...@linaro.org>
Date: Tue, 31 Mar 2015 10:16:46 +0530
Subject: [PATCH 1/2] dma: pl330: change busy marker for threads
Instead of a boolean flag to mark a thread busy, use the owner of
the thread as the marker. For free/available threads, the owner is
NULL. This will be useful in finding which channel owns a given
thread.
Signed-off-by: Jassi Brar <jaswinder.si...@linaro.org>
---
drivers/dma/pl330.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 0e1f567..d1f777e 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -369,8 +369,7 @@ struct _pl330_tbd {
struct pl330_thread {
u8 id;
int ev;
- /* If the channel is not yet acquired by any client */
- bool free;
+ struct dma_pl330_chan *pch;
/* Parent DMAC */
struct pl330_dmac *dmac;
/* Only two at a time */
@@ -1648,7 +1647,8 @@ static bool _chan_ns(const struct pl330_dmac *pl330, int i)
/* Upon success, returns IdentityToken for the
* allocated channel, NULL otherwise.
*/
-static struct pl330_thread *pl330_request_channel(struct pl330_dmac *pl330)
+static struct pl330_thread *pl330_request_channel(struct pl330_dmac *pl330,
+ struct dma_pl330_chan *pch)
{
struct pl330_thread *thrd = NULL;
unsigned long flags;
@@ -1663,11 +1663,11 @@ static struct pl330_thread *pl330_request_channel(struct pl330_dmac *pl330)
for (i = 0; i < chans; i++) {
thrd = &pl330->channels[i];
- if ((thrd->free) && (!_manager_ns(thrd) ||
+ if (!thrd->pch && (!_manager_ns(thrd) ||
_chan_ns(pl330, i))) {
thrd->ev = _alloc_event(thrd);
if (thrd->ev >= 0) {
- thrd->free = false;
+ thrd->pch = pch;
thrd->lstenq = 1;
thrd->req[0].desc = NULL;
thrd->req[1].desc = NULL;
@@ -1699,7 +1699,7 @@ static void pl330_release_channel(struct pl330_thread *thrd)
struct pl330_dmac *pl330;
unsigned long flags;
- if (!thrd || thrd->free)
+ if (!thrd || !thrd->pch)
return;
_stop(thrd);
@@ -1711,7 +1711,7 @@ static void pl330_release_channel(struct pl330_thread *thrd)
spin_lock_irqsave(&pl330->lock, flags);
_free_event(thrd, thrd->ev);
- thrd->free = true;
+ thrd->pch = NULL;
spin_unlock_irqrestore(&pl330->lock, flags);
}
@@ -1797,14 +1797,14 @@ static int dmac_alloc_threads(struct pl330_dmac *pl330)
thrd->id = i;
thrd->dmac = pl330;
_reset_thread(thrd);
- thrd->free = true;
+ thrd->pch = NULL;
}
/* MANAGER is indexed at the end */
thrd = &pl330->channels[chans];
thrd->id = chans;
thrd->dmac = pl330;
- thrd->free = false;
+ thrd->pch = NULL;
pl330->manager = thrd;
return 0;
@@ -2082,7 +2082,7 @@ static int pl330_alloc_chan_resources(struct dma_chan *chan)
dma_cookie_init(chan);
pch->cyclic = false;
- pch->thread = pl330_request_channel(pl330);
+ pch->thread = pl330_request_channel(pl330, pch);
if (!pch->thread) {
spin_unlock_irqrestore(&pch->lock, flags);
return -ENOMEM;
--
1.9.1
From 2cd6bf6748f28008a1650dca57a8f14b27283803 Mon Sep 17 00:00:00 2001
From: Jassi Brar <jaswinder.si...@linaro.org>
Date: Tue, 31 Mar 2015 10:21:14 +0530
Subject: [PATCH 2/2] dma: pl330: fix race between trigger and completion
We need to hold the lock on channel in ISR to prevent it
racing against the trigger call on the channel.
Reported-by: Scott Branden <sbran...@broadcom.com>
Signed-off-by: Jassi Brar <jaswinder.si...@linaro.org>
---
drivers/dma/pl330.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index d1f777e..ce40677 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -1573,6 +1573,7 @@ static int pl330_update(struct pl330_dmac *pl330)
if (val & (1 << ev)) { /* Event occurred */
struct pl330_thread *thrd;
u32 inten = readl(regs + INTEN);
+ unsigned long flag;
int active;
/* Clear the event */
@@ -1584,10 +1585,13 @@ static int pl330_update(struct pl330_dmac *pl330)
id = pl330->events[ev];
thrd = &pl330->channels[id];
+ spin_lock_irqsave(&thrd->pch->lock, flag);
active = thrd->req_running;
- if (active == -1) /* Aborted */
+ if (active == -1) { /* Aborted */
+ spin_unlock_irqrestore(&thrd->pch->lock, flag);
continue;
+ }
/* Detach the req */
descdone = thrd->req[active].desc;
@@ -1600,6 +1604,7 @@ static int pl330_update(struct pl330_dmac *pl330)
/* For now, just make a list of callbacks to be done */
list_add_tail(&descdone->rqd, &pl330->req_done);
+ spin_unlock_irqrestore(&thrd->pch->lock, flag);
}
}
--
1.9.1
