[PATCH 1/2] dma/ep93xx_dma: fix initialization of M2M control register

[PATCH 1/2] dma/ep93xx_dma: fix initialization of M2M control register

[Mika Westerberg]

From: Rafal Prylowski <prylowski@metasoft.pl>

Setting the flags in case of IDE didn't have any effect since the control
register is overwritten few lines below. So move these to be after the control
register is initialized.

Signed-off-by: Rafal Prylowski <prylowski@metasoft.pl>
Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
---
Rafal,

I hope you don't mind that I added your Signed-of-by to the patches. After all
they both came from you :)

 drivers/dma/ep93xx_dma.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index b47e2b8..6181811 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -459,10 +459,6 @@ static int m2m_hw_setup(struct ep93xx_dma_chan *edmac)
 		 * This IDE part is totally untested. Values below are taken
 		 * from the EP93xx Users's Guide and might not be correct.
 		 */
-		control |= M2M_CONTROL_NO_HDSK;
-		control |= M2M_CONTROL_RSS_IDE;
-		control |= M2M_CONTROL_PW_16;
-
 		if (data->direction == DMA_TO_DEVICE) {
 			/* Worst case from the UG */
 			control = (3 << M2M_CONTROL_PWSC_SHIFT);
@@ -473,6 +469,10 @@ static int m2m_hw_setup(struct ep93xx_dma_chan *edmac)
 			control |= M2M_CONTROL_SAH;
 			control |= M2M_CONTROL_TM_RX;
 		}
+
+		control |= M2M_CONTROL_NO_HDSK;
+		control |= M2M_CONTROL_RSS_IDE;
+		control |= M2M_CONTROL_PW_16;
 		break;
 
 	default:
-- 
1.7.7

[PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to access empty list

[Mika Westerberg]

From: Rafal Prylowski <prylowski@metasoft.pl>

If dma_terminate_all() is called before the ep93xx_dma_tasklet() gets to run,
it tries to access an empty ->active list causing following OOPS:

  Internal error: Oops - undefined instruction: 0 [#1]
  CPU: 0    Not tainted  (3.2.0-rc1EP-1+ #1008)
  PC is at 0xc184c868
  LR is at ep93xx_dma_tasklet+0xec/0x164
  pc : [<c184c868>]    lr : [<c012b528>]    psr: 00000013
  sp : c02b7e70  ip : ffffffff  fp : c02b7ea4
  r10: 00000100  r9 : 80000013  r8 : c02b7e50
  r7 : c02b7e70  r6 : c02b7ea4  r5 : 000000a4  r4 : c02b7e70
  r3 : c02b751d  r2 : 8ae34598  r1 : c184c6e0  r0 : c02b7ea4
  Flags: nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
  Control: c000717f  Table: c0004000  DAC: 00000017
  Process swapper (pid: 0, stack limit = 0xc02b6270)
  Stack: (0xc02b7e70 to 0xc02b8000)
  7e60:                                     c02b7ea4 c02b7e70 c0008b64 c02bd5c4
  7e80: c02d60e0 00000000 00000000 c02bd44c c02d60e0 00000100 c02b7ec4 c02b7ea8
  7ea0: c001c49c c012b44c 00000018 00000001 c02d60e0 c02b6000 c02b7f04 c02b7ec8
  7ec0: c001cbc0 c001c3e4 c02b7eec c02b7ed8 00000006 0000000a c02bf674 c02c458c
  7ee0: 00000011 00000000 c02b7f7c c0004000 41129200 c02b0c80 c02b7f14 c02b7f08
  7f00: c001cdd0 c001cb38 c02b7f34 c02b7f18 c000983c c001cd98 c0009a60 60000013
  7f20: fefb0001 c02b7f7c c02b7f44 c02b7f38 c0008190 c0009810 c02b7f9c c02b7f48
  7f40: c0008b64 c0008190 c02c2bf8 00000002 c02b7f90 60000013 c02b6000 c02d1504
  7f60: c02baa88 c02baa80 c0004000 41129200 c02b0c80 c02b7f9c c02b7fa0 c02b7f90
  7f80: c0009a54 c0009a60 60000013 ffffffff c02b7fbc c02b7fa0 c000a03c c0009a40
  7fa0: c02b80b0 c02b19dc c02b19d8 c02baa80 c02b7fcc c02b7fc0 c02384e4 c0009fd4
  7fc0: c02b7ff4 c02b7fd0 c029d924 c0238494 c029d49c 00000000 00000000 c02b19dc
  7fe0: c0007175 c02b803c 00000000 c02b7ff8 c000803c c029d700 00000000 00000000
  Backtrace:
  [<c012b43c>] (ep93xx_dma_tasklet+0x0/0x164) from [<c001c49c>] (tasklet_action+0xc8/0xdc)
  [<c001c3d4>] (tasklet_action+0x0/0xdc) from [<c001cbc0>] (__do_softirq+0x98/0x154)
   r7:c02b6000 r6:c02d60e0 r5:00000001 r4:00000018
  [<c001cb28>] (__do_softirq+0x0/0x154) from [<c001cdd0>] (irq_exit+0x48/0x50)
  [<c001cd88>] (irq_exit+0x0/0x50) from [<c000983c>] (handle_IRQ+0x3c/0x8c)
  [<c0009800>] (handle_IRQ+0x0/0x8c) from [<c0008190>] (asm_do_IRQ+0x10/0x14)
   r7:c02b7f7c r6:fefb0001 r5:60000013 r4:c0009a60
  [<c0008180>] (asm_do_IRQ+0x0/0x14) from [<c0008b64>] (__irq_svc+0x24/0xc0)
  Exception stack(0xc02b7f48 to 0xc02b7f90)
  7f40:                   c02c2bf8 00000002 c02b7f90 60000013 c02b6000 c02d1504
  7f60: c02baa88 c02baa80 c0004000 41129200 c02b0c80 c02b7f9c c02b7fa0 c02b7f90
  7f80: c0009a54 c0009a60 60000013 ffffffff
  [<c0009a30>] (default_idle+0x0/0x34) from [<c000a03c>] (cpu_idle+0x78/0xb0)
  [<c0009fc4>] (cpu_idle+0x0/0xb0) from [<c02384e4>] (rest_init+0x60/0x78)
   r7:c02baa80 r6:c02b19d8 r5:c02b19dc r4:c02b80b0
  [<c0238484>] (rest_init+0x0/0x78) from [<c029d924>] (start_kernel+0x234/0x278)
  [<c029d6f0>] (start_kernel+0x0/0x278) from [<c000803c>] (0xc000803c)
   r5:c02b803c r4:c0007175
  Code: 42555300 54535953 643d4d45 65766972 (53007372)

As we expect that the ->active list is never empty when the ep93xx_dma_tasklet()
is called, we fix this by adding a new flag per channel EP93XX_DMA_IS_RUNNING
which determines whether the channel is running or not.

We also add BUG_ON() to ep93xx_dma_get_active() to make sure that similar
problems will be caught early.

Signed-off-by: Rafal Prylowski <prylowski@metasoft.pl>
[added a flag instead of just checking for empty list]
Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
---
 drivers/dma/ep93xx_dma.c |   25 ++++++++++++++++---------
 1 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index 6181811..cc3a302 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -155,6 +155,8 @@ struct ep93xx_dma_chan {
 	unsigned long			flags;
 /* Channel is configured for cyclic transfers */
 #define EP93XX_DMA_IS_CYCLIC		0
+/* Channel is enabled */
+#define EP93XX_DMA_IS_RUNNING		1
 
 	int				buffer;
 	dma_cookie_t			last_completed;
@@ -246,6 +248,7 @@ static void ep93xx_dma_set_active(struct ep93xx_dma_chan *edmac,
 static struct ep93xx_dma_desc *
 ep93xx_dma_get_active(struct ep93xx_dma_chan *edmac)
 {
+	BUG_ON(list_empty(&edmac->active));
 	return list_first_entry(&edmac->active, struct ep93xx_dma_desc, node);
 }
 
@@ -669,24 +672,25 @@ static void ep93xx_dma_tasklet(unsigned long data)
 {
 	struct ep93xx_dma_chan *edmac = (struct ep93xx_dma_chan *)data;
 	struct ep93xx_dma_desc *desc, *d;
-	dma_async_tx_callback callback;
-	void *callback_param;
+	dma_async_tx_callback callback = NULL;
+	void *callback_param = NULL;
 	LIST_HEAD(list);
 
 	spin_lock_irq(&edmac->lock);
-	desc = ep93xx_dma_get_active(edmac);
-	if (desc->complete) {
-		edmac->last_completed = desc->txd.cookie;
-		list_splice_init(&edmac->active, &list);
+	if (test_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags)) {
+		desc = ep93xx_dma_get_active(edmac);
+		if (desc->complete) {
+			edmac->last_completed = desc->txd.cookie;
+			list_splice_init(&edmac->active, &list);
+		}
+		callback = desc->txd.callback;
+		callback_param = desc->txd.callback_param;
 	}
 	spin_unlock_irq(&edmac->lock);
 
 	/* Pick up the next descriptor from the queue */
 	ep93xx_dma_advance_work(edmac);
 
-	callback = desc->txd.callback;
-	callback_param = desc->txd.callback_param;
-
 	/* Now we can release all the chained descriptors */
 	list_for_each_entry_safe(desc, d, &list, node) {
 		/*
@@ -758,6 +762,8 @@ static dma_cookie_t ep93xx_dma_tx_submit(struct dma_async_tx_descriptor *tx)
 	edmac->chan.cookie = cookie;
 	desc->txd.cookie = cookie;
 
+	set_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags);
+
 	/*
 	 * If nothing is currently prosessed, we push this descriptor
 	 * directly to the hardware. Otherwise we put the descriptor
@@ -1106,6 +1112,7 @@ static int ep93xx_dma_terminate_all(struct ep93xx_dma_chan *edmac)
 	spin_lock_irqsave(&edmac->lock, flags);
 	/* First we disable and flush the DMA channel */
 	edmac->edma->hw_shutdown(edmac);
+	clear_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags);
 	clear_bit(EP93XX_DMA_IS_CYCLIC, &edmac->flags);
 	list_splice_init(&edmac->active, &list);
 	list_splice_init(&edmac->queue, &list);
-- 
1.7.7

RE: [PATCH 1/2] dma/ep93xx_dma: fix initialization of M2M control register

[H Hartley Sweeten]

On Tuesday, November 22, 2011 12:46 PM, Mika Westerberg wrote:
> From: Rafal Prylowski <prylowski@metasoft.pl>
> 
> Setting the flags in case of IDE didn't have any effect since the control
> register is overwritten few lines below. So move these to be after the control
> register is initialized.
> 
> Signed-off-by: Rafal Prylowski <prylowski@metasoft.pl>
> Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>

Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>

RE: [PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to access empty list

[H Hartley Sweeten]

On Tuesday, November 22, 2011 12:46 PM, Mika Westerberg wrote:
> From: Rafal Prylowski <prylowski@metasoft.pl>
>
> If dma_terminate_all() is called before the ep93xx_dma_tasklet() gets to run,
> it tries to access an empty ->active list causing following OOPS:

[snip]

> As we expect that the ->active list is never empty when the ep93xx_dma_tasklet()
> is called, we fix this by adding a new flag per channel EP93XX_DMA_IS_RUNNING
> which determines whether the channel is running or not.
> 
> We also add BUG_ON() to ep93xx_dma_get_active() to make sure that similar
> problems will be caught early.
> 
> Signed-off-by: Rafal Prylowski <prylowski@metasoft.pl>
> [added a flag instead of just checking for empty list]
> Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
> ---
>  drivers/dma/ep93xx_dma.c |   25 ++++++++++++++++---------
>  1 files changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
> index 6181811..cc3a302 100644
> --- a/drivers/dma/ep93xx_dma.c
> +++ b/drivers/dma/ep93xx_dma.c
> @@ -155,6 +155,8 @@ struct ep93xx_dma_chan {
>  	unsigned long			flags;
>  /* Channel is configured for cyclic transfers */
>  #define EP93XX_DMA_IS_CYCLIC		0
> +/* Channel is enabled */
> +#define EP93XX_DMA_IS_RUNNING		1
>  
>  	int				buffer;
>  	dma_cookie_t			last_completed;
> @@ -246,6 +248,7 @@ static void ep93xx_dma_set_active(struct ep93xx_dma_chan *edmac,
>  static struct ep93xx_dma_desc *
>  ep93xx_dma_get_active(struct ep93xx_dma_chan *edmac)
>  {
> +	BUG_ON(list_empty(&edmac->active));
>  	return list_first_entry(&edmac->active, struct ep93xx_dma_desc, node);

Mika,

Thanks for looking into this.

I still don't like the BUG_ON here.  Is it even possible to get here with
an empty list now that your catching it in the tasklet?

But, ep93xx_dma_set_active() also has a BUG_ON test so...

Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>

Re: [PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to access empty list

[Mika Westerberg]

On Tue, Nov 22, 2011 at 02:26:52PM -0600, H Hartley Sweeten wrote:
> 
> I still don't like the BUG_ON here.  Is it even possible to get here with
> an empty list now that your catching it in the tasklet?

It's there just to make sure that we don't corrupt any memory if the list is
empty because of some other, yet unknown, bug.

> 
> But, ep93xx_dma_set_active() also has a BUG_ON test so...
> 
> Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>

Thanks.

Re: [PATCH 1/2] dma/ep93xx_dma: fix initialization of M2M control register

[Rafal Prylowski]

On 2011-11-22 20:45, Mika Westerberg wrote:
> Rafal,
> 
> I hope you don't mind that I added your Signed-of-by to the patches. After all
> they both came from you :)

No, I don't mind :)
Thanks.

RE: [PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to access empty list

[Vinod Koul]

On Tue, 2011-11-22 at 14:26 -0600, H Hartley Sweeten wrote:
> On Tuesday, November 22, 2011 12:46 PM, Mika Westerberg wrote:
> > From: Rafal Prylowski <prylowski@metasoft.pl>
> >
> > If dma_terminate_all() is called before the ep93xx_dma_tasklet()
> gets to run,
> > it tries to access an empty ->active list causing following OOPS:
> 
> [snip]
> 
> > As we expect that the ->active list is never empty when the
> ep93xx_dma_tasklet()
> > is called, we fix this by adding a new flag per channel
> EP93XX_DMA_IS_RUNNING
> > which determines whether the channel is running or not.
> > 
> > We also add BUG_ON() to ep93xx_dma_get_active() to make sure that
> similar
> > problems will be caught early. 
My $0.02

will you still hit the problem if you do a proper check in tasklet for 
a) if list is empty
b) if _get_active_desc() returns valid desc
and the _get_active_desc() returns NULL on not finding active desc

The point is by adding a flag you are avoiding the condition hence it is
working for you whereas on other approach you exit gracefully without
crashing in all the cases (including potentially uncovered ones)


-- 
~Vinod

Re: [PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to access empty list

[Mika Westerberg]

On Wed, Nov 23, 2011 at 04:30:34PM +0530, Vinod Koul wrote:
> 
> will you still hit the problem if you do a proper check in tasklet for 
> a) if list is empty
> b) if _get_active_desc() returns valid desc
> and the _get_active_desc() returns NULL on not finding active desc

No, with the above the problem goes away.

> The point is by adding a flag you are avoiding the condition hence it is
> working for you whereas on other approach you exit gracefully without
> crashing in all the cases (including potentially uncovered ones)

Ok I see.

I'll prepare a new version where ep93xx_dma_get_active() returns NULL in case
of empty active list, and handle it properly in callers.