Re: [RFC][media] s5p-fimc : Need to modify for s5pv310

Re: [RFC][media] s5p-fimc : Need to modify for s5pv310

[Sylwester Nawrocki]

Hi Sungchun,

On 12/10/2010 03:21 AM, Sungchun Kang wrote:
> 
> 
>> -----Original Message-----
>> From: linux-media-owner@vger.kernel.org [mailto:linux-media-
>> owner@vger.kernel.org] On Behalf Of Sylwester Nawrocki
>> Sent: Monday, December 06, 2010 6:46 PM
>> To: sungchun.kang@samsung.com
>> Cc: linux-media@vger.kernel.org
>> Subject: Re: [RFC][media] s5p-fimc : Need to modify for s5pv310
>>
>> Hi Sungchun,
>>
>> thanks for your suggestions.
>> I am planning to improve output DMA handling in the fimc camera
>> capture driver,
>> what is done already is only a minimal adaptation to make driver work
>> on
>> S5PV310 SoC. We don't even have a platform support (resource and
>> platform
>> device definitions) for FIMC@S5PV310 yet though. I think it needs to
>> be done first.
>>
>> Your proposed scheme of presetting output DMA buffer adresses before
>> streaming
>> is enabled and then using the CIFCNTSEQ register to mask out buffers
>> passed
>> to user space looks reasonable to me. I could imagine adopting such a
>> method
>> for buffer of V4L2_MEMORY_MMAP memory type. But do you think it is
>> going to
>> work for V4L2_MEMORY_USERPTR? There is no confidence that USERPTR
>> addresses
>> passed by applications in subsequent VIDIOC_QBUF calls will not be
>> changing,
>> right?
> 
> Like V4L2_MEMORY_MMAP, it is possible to use V4L2_MEMORY_USERPTR for memory type.
> Surely, in case of V4L2_MEMORY_USERPTR, output buffer SFR could be changed.
> But, it is possible to adjust my concept too.
> When the VIDIOC_QBUF called, user can set m.userptr field to the address of the buffer, 
> length to its size, and index field. 
> 
> <For example QBUF>
> 
> Output DMASFR		index	 	m.userptr		CIFCNTSEQ[bit]
> CIOYSA1			0		0x40000000		[0] - enable
> CIOYSA2			1		0x40001000		[1] - enable
> CIOYSA3			2		0x40002000		[2] - enable
> CIOYSA4			3		0x40003000		[3] - enable
> CIOYSA5			4		0x40004000		[4] - enable
> CIOYSA6			5		0x40005000		[5] - enable
> CIOYSA1			0		0x40006000		[0] - enable (SFR value change for output buffer)
> 
> Because it is possible to regard a index as output DMA SFR, there's no need to use pending queue concept.

I do not really see much gain in that approach, we still need to obtain
physical address from video buffer, read the address from registers, compare
both and then perform write if necessary.
The code would be different among various SoC revisions and it would increase
interrupt service routine size.
I would see CIFCNTSEQ as a means of additional protection preventing the DMA
engine from writing to a buffer which has been passed to user land.

Please note that if user does not queue the buffers in an ascending buffer
index order, the buffers are going to be dequeued out of order.
Since we cannot change the order of processing the buffers in hardware,
we are only able to mask/unmask specific buffer in the DMA engine.
The processing sequence is always fixed and the buffers would be dequeued
in an ascending video buffer index order.
However this kind of operation is possible with videobuf2.

The modification for s5pv310 is rather straightforward. I am more concerned
at the moment with the fact that in s5pv210 output frame index register
seem to be changing in a non deterministic way when the CIOYSAn address
registers are being updated in the interrupt handler. So it looks like there is
no reliable status register in HW to determine which DMA buffer is currently
being used. This causes trouble when streaming is stopped in the camera capture
driver when user does not queue buffer on time, and then
the capturing needs to be resumed. Are you aware of that?
The only resolution I could come up with so far is to create a parallel counter
in software, but it is not really reliable.

> 
> How about this?
> First I am going to modify output buffer control in V310, and you review that.
> 
> I saw the patches vb2(ver. 6) and fimc patch. I will work based on that.
> 
> 
>> So we would have to walk the list of buffers' addresses written into
>> CIOYSAn
>> registers and perform a write if our new incoming buffer is not there
>> anyway.
>>
>> Nevertheless I think it would be cleaner and more safe to use your
>> proposed
>> method. Did you observe any problems when DMA buffers addresses are
>> reconfigured within the ISR in S5PV310? I mean are there any good
>> reasons
>> against that? I know there are some issues on S5PV210 about that and
>> I am going fix it too.
>>
>> On 12/03/2010 08:30 AM, Sungchun Kang wrote:
>>> Hi Sylwester Nawrocki,
>>>
>>> I have some suggestion about s5p-fimc camera driver.
>>> As you know, FIMC have 32 ping-pong register(CIOYSA1~CIOYSA32) for
>> output
>>> buffer in v310 chip. It is different from v210.
>>> It is not necessary to change address at ping-pong register.
>>> If request buffer number is 8, 8 buffer can be set at ping-pong
>> register.
>>>
>>> - active_buf_q / pending_buf_q
>>>
>>> The list_head pending_buf_q is not necessary for v310. Because, it
>> is possible
>>> to set output buffer until 32.
>>> There is no case that request buffer number is over 32.
>>
>> Ok, I think it is safe to make such assumption.
>>
>>> So, I think pending_buf_q is not use in v310. Instead, it can be
>> used active_buf_q.
>>> Of course, The use of active_buf_q may be different from the present.
>>>
>>> For intstance, ISR may be changed follow.
>>>
>>> a. Read FrameCnt_before(CISTATUS2) - This is for what is written
>> buffer(index) just.
>>> b. Disable a proper bit of FrameCnt_Seq(CIFCNTSEQ) and send written
>> buffer to done_list.
>>> ....
>> And we we wanted to reschedule same buffer again we would have to
>> search in
>> all 32 registers to match the address of a buffer passed back by the
>> application, right?
>>
>>>
>>> I want to know how about your opinions.
>>
>> In general I would like to avoid significant differences of hardware
>> handling
>> across various SoC variants as much as possible. However also I
>> realize that
>> some differences cannot be avoided for optimal hardware handling.
>> And please feel free to submit patches, however I think the best time
>> for those
>> would be after the driver is adopted to videobuf2. Now it is changing
>> frequently.
>>
>> Regards,
>> Sylwester
>>
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-
>> media" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>
>> --
>> Sylwester Nawrocki
>> Samsung Poland R&D Center
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-media"
>> in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 
Regards,
-- 
Sylwester Nawrocki
Samsung Poland R&D Center

RE: [RFC][media] s5p-fimc : Need to modify for s5pv310

[Sungchun Kang]

Hi Sylwester,
Thanks for your reply.
I almost agree with your opinion.

On 12/13/2010 07:46 PM, Sylwester Nawrocki wrote:
> -----Original Message-----
> From: linux-media-owner@vger.kernel.org [mailto:linux-media-
> owner@vger.kernel.org] On Behalf Of Sylwester Nawrocki
> Sent: Monday, December 13, 2010 7:46 PM
> To: sungchun.kang@samsung.com
> Cc: linux-media@vger.kernel.org
> Subject: Re: [RFC][media] s5p-fimc : Need to modify for s5pv310
> 
> 
> Hi Sungchun,
> 
> On 12/10/2010 03:21 AM, Sungchun Kang wrote:
> >
> >
> >> -----Original Message-----
> >> From: linux-media-owner@vger.kernel.org [mailto:linux-media-
> >> owner@vger.kernel.org] On Behalf Of Sylwester Nawrocki
> >> Sent: Monday, December 06, 2010 6:46 PM
> >> To: sungchun.kang@samsung.com
> >> Cc: linux-media@vger.kernel.org
> >> Subject: Re: [RFC][media] s5p-fimc : Need to modify for s5pv310
> >>
> >> Hi Sungchun,
> >>
> >> thanks for your suggestions.
> >> I am planning to improve output DMA handling in the fimc camera
> >> capture driver,
> >> what is done already is only a minimal adaptation to make driver
> work
> >> on
> >> S5PV310 SoC. We don't even have a platform support (resource and
> >> platform
> >> device definitions) for FIMC@S5PV310 yet though. I think it needs
> to
> >> be done first.
> >>
> >> Your proposed scheme of presetting output DMA buffer adresses
> before
> >> streaming
> >> is enabled and then using the CIFCNTSEQ register to mask out
> buffers
> >> passed
> >> to user space looks reasonable to me. I could imagine adopting such
> a
> >> method
> >> for buffer of V4L2_MEMORY_MMAP memory type. But do you think it is
> >> going to
> >> work for V4L2_MEMORY_USERPTR? There is no confidence that USERPTR
> >> addresses
> >> passed by applications in subsequent VIDIOC_QBUF calls will not be
> >> changing,
> >> right?
> >
> > Like V4L2_MEMORY_MMAP, it is possible to use V4L2_MEMORY_USERPTR for
> memory type.
> > Surely, in case of V4L2_MEMORY_USERPTR, output buffer SFR could be
> changed.
> > But, it is possible to adjust my concept too.
> > When the VIDIOC_QBUF called, user can set m.userptr field to the
> address of the buffer,
> > length to its size, and index field.
> >
> > <For example QBUF>
> >
> > Output DMASFR		index	 	m.userptr		CIFCNTSEQ[bit]
> > CIOYSA1			0		0x40000000		[0] - enable
> > CIOYSA2			1		0x40001000		[1] - enable
> > CIOYSA3			2		0x40002000		[2] - enable
> > CIOYSA4			3		0x40003000		[3] - enable
> > CIOYSA5			4		0x40004000		[4] - enable
> > CIOYSA6			5		0x40005000		[5] - enable
> > CIOYSA1			0		0x40006000		[0] - enable
> (SFR value change for output buffer)
> >
> > Because it is possible to regard a index as output DMA SFR, there's
> no need to use pending queue concept.
> 
> I do not really see much gain in that approach, we still need to
> obtain
> physical address from video buffer, read the address from registers,
> compare
> both and then perform write if necessary.


First of all, I wonder V4L2 standard as below.
Index field of v4l2_buffer is used not only V4L2_MEMORY_MMAP but also V4L2_MEMORY_USERPTR of vb2_qbuf.
But it is not described at V4L2 standard. 
What is right thing?

And in V4L2_MEMORY_USERPTR case, you're right.
But I doubt such case(change CIOYSAn's value)is existed.

> The code would be different among various SoC revisions and it would
> increase
> interrupt service routine size.
> I would see CIFCNTSEQ as a means of additional protection preventing
> the DMA
> engine from writing to a buffer which has been passed to user land.
> 
CIFCNTSEQ is for maximum 32 buffer count to user. User can select buffer count easier.

> Please note that if user does not queue the buffers in an ascending
> buffer
> index order, the buffers are going to be dequeued out of order.
> Since we cannot change the order of processing the buffers in hardware,
> we are only able to mask/unmask specific buffer in the DMA engine.
> The processing sequence is always fixed and the buffers would be
> dequeued
> in an ascending video buffer index order.
> However this kind of operation is possible with videobuf2.
> 
> The modification for s5pv310 is rather straightforward. I am more
> concerned
> at the moment with the fact that in s5pv210 output frame index
> register
> seem to be changing in a non deterministic way when the CIOYSAn
> address
> registers are being updated in the interrupt handler. So it looks like
> there is
> no reliable status register in HW to determine which DMA buffer is
> currently
> being used. This causes trouble when streaming is stopped in the
> camera capture
> driver when user does not queue buffer on time, and then
> the capturing needs to be resumed. Are you aware of that?
> The only resolution I could come up with so far is to create a
> parallel counter
> in software, but it is not really reliable.

Please tell me what is the parallel counter? 

OK, I will consider the reason using CIOYSAn over 4(n).
Because I did not find majority necessary it.
Once I try another point of patch about fimc capture driver for V310 using the variable "has_cistatus2".
As you know, it is necessary to separate V310 and V210 in fimc driver.
For instance, in V310, it is possible to read "before frame count" and "current frame count" in isr.
You did not used that.

> >
> > How about this?
> > First I am going to modify output buffer control in V310, and you
> review that.
> >
> > I saw the patches vb2(ver. 6) and fimc patch. I will work based on
> that.
> >
> >
> >> So we would have to walk the list of buffers' addresses written
> into
> >> CIOYSAn
> >> registers and perform a write if our new incoming buffer is not
> there
> >> anyway.
> >>
> >> Nevertheless I think it would be cleaner and more safe to use your
> >> proposed
> >> method. Did you observe any problems when DMA buffers addresses are
> >> reconfigured within the ISR in S5PV310? I mean are there any good
> >> reasons
> >> against that? I know there are some issues on S5PV210 about that
> and
> >> I am going fix it too.
> >>
> >> On 12/03/2010 08:30 AM, Sungchun Kang wrote:
> >>> Hi Sylwester Nawrocki,
> >>>
> >>> I have some suggestion about s5p-fimc camera driver.
> >>> As you know, FIMC have 32 ping-pong register(CIOYSA1~CIOYSA32) for
> >> output
> >>> buffer in v310 chip. It is different from v210.
> >>> It is not necessary to change address at ping-pong register.
> >>> If request buffer number is 8, 8 buffer can be set at ping-pong
> >> register.
> >>>
> >>> - active_buf_q / pending_buf_q
> >>>
> >>> The list_head pending_buf_q is not necessary for v310. Because, it
> >> is possible
> >>> to set output buffer until 32.
> >>> There is no case that request buffer number is over 32.
> >>
> >> Ok, I think it is safe to make such assumption.
> >>
> >>> So, I think pending_buf_q is not use in v310. Instead, it can be
> >> used active_buf_q.
> >>> Of course, The use of active_buf_q may be different from the
> present.
> >>>
> >>> For intstance, ISR may be changed follow.
> >>>
> >>> a. Read FrameCnt_before(CISTATUS2) - This is for what is written
> >> buffer(index) just.
> >>> b. Disable a proper bit of FrameCnt_Seq(CIFCNTSEQ) and send
> written
> >> buffer to done_list.
> >>> ....
> >> And we we wanted to reschedule same buffer again we would have to
> >> search in
> >> all 32 registers to match the address of a buffer passed back by
> the
> >> application, right?
> >>
> >>>
> >>> I want to know how about your opinions.
> >>
> >> In general I would like to avoid significant differences of
> hardware
> >> handling
> >> across various SoC variants as much as possible. However also I
> >> realize that
> >> some differences cannot be avoided for optimal hardware handling.
> >> And please feel free to submit patches, however I think the best
> time
> >> for those
> >> would be after the driver is adopted to videobuf2. Now it is
> changing
> >> frequently.
> >>
> >> Regards,
> >> Sylwester
> >>
> >>>
> >>> --
> >>> To unsubscribe from this list: send the line "unsubscribe linux-
> >> media" in
> >>> the body of a message to majordomo@vger.kernel.org
> >>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>>
> >>
> >> --
> >> Sylwester Nawrocki
> >> Samsung Poland R&D Center
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-
> media"
> >> in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> >
> Regards,
> --
> Sylwester Nawrocki
> Samsung Poland R&D Center
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media"
> in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [RFC][media] s5p-fimc : Need to modify for s5pv310

[Sylwester Nawrocki]

Hi Sungchun,

On 12/14/2010 10:52 AM, Sungchun Kang wrote:
> 
> Hi Sylwester,
> Thanks for your reply.
> I almost agree with your opinion.
> 
> On 12/13/2010 07:46 PM, Sylwester Nawrocki wrote:
>> -----Original Message-----
>> From: linux-media-owner@vger.kernel.org [mailto:linux-media-
>> owner@vger.kernel.org] On Behalf Of Sylwester Nawrocki
>> Sent: Monday, December 13, 2010 7:46 PM
>> To: sungchun.kang@samsung.com
>> Cc: linux-media@vger.kernel.org
>> Subject: Re: [RFC][media] s5p-fimc : Need to modify for s5pv310
>>
>>
>> Hi Sungchun,
>>
>> On 12/10/2010 03:21 AM, Sungchun Kang wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: linux-media-owner@vger.kernel.org [mailto:linux-media-
>>>> owner@vger.kernel.org] On Behalf Of Sylwester Nawrocki
>>>> Sent: Monday, December 06, 2010 6:46 PM
>>>> To: sungchun.kang@samsung.com
>>>> Cc: linux-media@vger.kernel.org
>>>> Subject: Re: [RFC][media] s5p-fimc : Need to modify for s5pv310
>>>>
>>>> Hi Sungchun,
>>>>
>>>> thanks for your suggestions.
>>>> I am planning to improve output DMA handling in the fimc camera
>>>> capture driver,
>>>> what is done already is only a minimal adaptation to make driver
>> work
>>>> on
>>>> S5PV310 SoC. We don't even have a platform support (resource and
>>>> platform
>>>> device definitions) for FIMC@S5PV310 yet though. I think it needs
>> to
>>>> be done first.
>>>>
>>>> Your proposed scheme of presetting output DMA buffer adresses
>> before
>>>> streaming
>>>> is enabled and then using the CIFCNTSEQ register to mask out
>> buffers
>>>> passed
>>>> to user space looks reasonable to me. I could imagine adopting such
>> a
>>>> method
>>>> for buffer of V4L2_MEMORY_MMAP memory type. But do you think it is
>>>> going to
>>>> work for V4L2_MEMORY_USERPTR? There is no confidence that USERPTR
>>>> addresses
>>>> passed by applications in subsequent VIDIOC_QBUF calls will not be
>>>> changing,
>>>> right?
>>>
>>> Like V4L2_MEMORY_MMAP, it is possible to use V4L2_MEMORY_USERPTR for
>> memory type.
>>> Surely, in case of V4L2_MEMORY_USERPTR, output buffer SFR could be
>> changed.
>>> But, it is possible to adjust my concept too.
>>> When the VIDIOC_QBUF called, user can set m.userptr field to the
>> address of the buffer,
>>> length to its size, and index field.
>>>
>>> <For example QBUF>
>>>
>>> Output DMASFR		index	 	m.userptr		CIFCNTSEQ[bit]
>>> CIOYSA1			0		0x40000000		[0] - enable
>>> CIOYSA2			1		0x40001000		[1] - enable
>>> CIOYSA3			2		0x40002000		[2] - enable
>>> CIOYSA4			3		0x40003000		[3] - enable
>>> CIOYSA5			4		0x40004000		[4] - enable
>>> CIOYSA6			5		0x40005000		[5] - enable
>>> CIOYSA1			0		0x40006000		[0] - enable
>> (SFR value change for output buffer)
>>>
>>> Because it is possible to regard a index as output DMA SFR, there's
>> no need to use pending queue concept.
>>
>> I do not really see much gain in that approach, we still need to
>> obtain
>> physical address from video buffer, read the address from registers,
>> compare
>> both and then perform write if necessary.
> 
> 
> First of all, I wonder V4L2 standard as below.
> Index field of v4l2_buffer is used not only V4L2_MEMORY_MMAP but also V4L2_MEMORY_USERPTR of vb2_qbuf.
> But it is not described at V4L2 standard. 
> What is right thing?

As already pointed out by Laurent the index field should be used
with either V4L2_MEMORY_MMAP or V4L2_MEMORY_USERPTR.
The specification will be soon corrected.

> 
> And in V4L2_MEMORY_USERPTR case, you're right.
> But I doubt such case(change CIOYSAn's value)is existed.

Although such a use case might be rare, it still needs to be handled
properly by the driver.

> 
>> The code would be different among various SoC revisions and it would
>> increase
>> interrupt service routine size.
>> I would see CIFCNTSEQ as a means of additional protection preventing
>> the DMA
>> engine from writing to a buffer which has been passed to user land.
>>
> CIFCNTSEQ is for maximum 32 buffer count to user. User can select buffer count easier.
> 
>> Please note that if user does not queue the buffers in an ascending
>> buffer
>> index order, the buffers are going to be dequeued out of order.
>> Since we cannot change the order of processing the buffers in hardware,
>> we are only able to mask/unmask specific buffer in the DMA engine.
>> The processing sequence is always fixed and the buffers would be
>> dequeued
>> in an ascending video buffer index order.
>> However this kind of operation is possible with videobuf2.
>>
>> The modification for s5pv310 is rather straightforward. I am more
>> concerned
>> at the moment with the fact that in s5pv210 output frame index
>> register
>> seem to be changing in a non deterministic way when the CIOYSAn
>> address
>> registers are being updated in the interrupt handler. So it looks like
>> there is
>> no reliable status register in HW to determine which DMA buffer is
>> currently
>> being used. This causes trouble when streaming is stopped in the
>> camera capture
>> driver when user does not queue buffer on time, and then
>> the capturing needs to be resumed. Are you aware of that?
>> The only resolution I could come up with so far is to create a
>> parallel counter
>> in software, but it is not really reliable.
> 
> Please tell me what is the parallel counter? 

It is a variable in software incremented in every interrupt routine call.
Although if an interrupt is missed it can get out of sync with the hardware.

> 
> OK, I will consider the reason using CIOYSAn over 4(n).
> Because I did not find majority necessary it.
> Once I try another point of patch about fimc capture driver for V310 using the variable "has_cistatus2".
> As you know, it is necessary to separate V310 and V210 in fimc driver.
> For instance, in V310, it is possible to read "before frame count" and "current frame count" in isr.
> You did not used that.

Are you talking about works on top of this patch?
http://git.infradead.org/users/kmpark/linux-2.6-samsung/commitdiff/63e434150d84ea9d76efd0e48ad5543cbcf779fa

Yes, it still can be improved, I am no saying no. But I prefer not to
create too much IP revision specific code for the common functionality.
And it would be good to have some hardware details hidden in common functions
used to implement algorithms along as many hardware revisions as possible.

If you have already done some works to improve DMA handling, patches are
welcomed. Ideally if they account the last bugfix patches, which are available
in repository

git://git.infradead.org/users/kmpark/linux-2.6-samsung s5p_fimc_fixes_for_2.6.37

after commit  a348e9110ddb5d494e060d989b35dd1f35359d58
[media] cx25840: fix problem with Terratec Grabster AV400

Thanks,
Sylwester

> 
>>>
>>> How about this?
>>> First I am going to modify output buffer control in V310, and you
>> review that.
>>>
>>> I saw the patches vb2(ver. 6) and fimc patch. I will work based on
>> that.
>>>
>>>
>>>> So we would have to walk the list of buffers' addresses written
>> into
>>>> CIOYSAn
>>>> registers and perform a write if our new incoming buffer is not
>> there
>>>> anyway.
>>>>
>>>> Nevertheless I think it would be cleaner and more safe to use your
>>>> proposed
>>>> method. Did you observe any problems when DMA buffers addresses are
>>>> reconfigured within the ISR in S5PV310? I mean are there any good
>>>> reasons
>>>> against that? I know there are some issues on S5PV210 about that
>> and
>>>> I am going fix it too.
>>>>
>>>> On 12/03/2010 08:30 AM, Sungchun Kang wrote:
>>>>> Hi Sylwester Nawrocki,
>>>>>
>>>>> I have some suggestion about s5p-fimc camera driver.
>>>>> As you know, FIMC have 32 ping-pong register(CIOYSA1~CIOYSA32) for
>>>> output
>>>>> buffer in v310 chip. It is different from v210.
>>>>> It is not necessary to change address at ping-pong register.
>>>>> If request buffer number is 8, 8 buffer can be set at ping-pong
>>>> register.
>>>>>
>>>>> - active_buf_q / pending_buf_q
>>>>>
>>>>> The list_head pending_buf_q is not necessary for v310. Because, it
>>>> is possible
>>>>> to set output buffer until 32.
>>>>> There is no case that request buffer number is over 32.
>>>>
>>>> Ok, I think it is safe to make such assumption.
>>>>
>>>>> So, I think pending_buf_q is not use in v310. Instead, it can be
>>>> used active_buf_q.
>>>>> Of course, The use of active_buf_q may be different from the
>> present.
>>>>>
>>>>> For intstance, ISR may be changed follow.
>>>>>
>>>>> a. Read FrameCnt_before(CISTATUS2) - This is for what is written
>>>> buffer(index) just.
>>>>> b. Disable a proper bit of FrameCnt_Seq(CIFCNTSEQ) and send
>> written
>>>> buffer to done_list.
>>>>> ....
>>>> And we we wanted to reschedule same buffer again we would have to
>>>> search in
>>>> all 32 registers to match the address of a buffer passed back by
>> the
>>>> application, right?
>>>>
>>>>>
>>>>> I want to know how about your opinions.
>>>>
>>>> In general I would like to avoid significant differences of
>> hardware
>>>> handling
>>>> across various SoC variants as much as possible. However also I
>>>> realize that
>>>> some differences cannot be avoided for optimal hardware handling.
>>>> And please feel free to submit patches, however I think the best
>> time
>>>> for those
>>>> would be after the driver is adopted to videobuf2. Now it is
>> changing
>>>> frequently.
>>>>
-- 
Sylwester Nawrocki
Samsung Poland R&D Center