question: CSI on imx8mq with (any) CSI2 camera / experience with mx6s_capture?

Martin Kepplinger martin.kepplinger at
Tue Dec 22 09:06:28 EST 2020

On 10.12.20 17:04, Laurent Pinchart wrote:
> Hi Martin,
> On Thu, Dec 10, 2020 at 02:12:30PM +0100, Martin Kepplinger wrote:
>> On 10.12.20 13:17, Laurent Pinchart wrote:
>>> On Thu, Dec 10, 2020 at 11:24:00AM +0200, Laurent Pinchart wrote:
>>>> On Thu, Dec 10, 2020 at 09:17:48AM +0100, Martin Kepplinger wrote:
>>>>> hi,
>>>>> TL;DR: did you use the NXP "mx6s_capture" csi bridge driver with other
>>>>> cameras?
>>>> I've recently worked on camera support for i.MX8MM (whose camera IP
>>>> cores are, if not identical, very similar to the i.MX8MQ's). The least I
>>>> can say is that it was painful :-(
>>>> I'm using an MT9M114 sensor, which can produce RAW8, RAW10 and YUV and
>>>> has a CSI-2 interface. My first use case is to capture RAW10, which
>>>> isn't supported by the mx6s_capture driver.
>> so did you successfully use the NXP mx6s_capture driver with that sensor
>> too?
> I haven't tried. The mx6s_capture driver and the mainline driver share a
> similar architecture, as they came from the same code base. They have
> diverged, with the  mainline driver receiving bug fixes and new
> features, and my large no-yet-upstreamed patch series adds lots of fixes
> that are required for the mt9m114 driver to work with the driver. For
> that reason, I've considered that porting the mt9m114 driver to the NXP
> mx6s_capture, and fixing the same issues in the mx6s_capture driver than
> were present in the mainline driver, would require lots of time for
> likely very little gain.
> That being said, I've compared the two drivers, and I haven't seen
> anything in mx6s_capture that would address the specific issues I'm
> facing. I've ordered yesterday an i.MX8MM EVK with an OV5640 camera
> module, and I will test those with the mainline driver. If they don't
> work, and assuming the NXP kernel driver works on that platform, I'll
> have two code bases to compare.
>>>>> I try to use a CSI2 camera (hi846 I'm writing a driver for) on imx8mq:
>>>>> Using NXP's CSI bridge driver
>>>>> as well as the CSI driver itself:
>>>>> works fine when using the ov5640 camera with this driver:
>>>>> (I realize there is a CSI bridge driver in staging, but that need more
>>>>> work to be actually used. Of course after this the goal is to fix and
>>>>> use it; and mainline a CSI phy driver too.)
>>>> I have lots of patches for this driver, which I've developed on i.MX7D
>>>> for a separate project. I'd like to mainline them, but this is blocked
>>>> by one last issue that I haven't been able to solve yet. In a nutshell,
>>>> the CSI writes two consecutive frames in each buffer, overflowing the
>>>> allocated memory. The registers that control the buffer size seem to be
>>>> programmed correctly as far as I can tell. I've reported this issue to
>>>> NXP but haven't received any feedback yet.
>> that's different from where I am. So you don't get any interrupt (EOF or
>> other) when only *one* frame is written into one buffer?
> I don't get any FB1_DMA_DONE or FB2_DMA_DONE interrupt at least. I
> haven't checked other interrupts. I thus get half of the frame rate. If
> I configure the CSI_CSIIMAG_PARA register with half of the actual image
> height, buffers then contain a single image and the frame rate goes to
> the expected value. That gives me a workaround, but without
> understanding the root cause, I'm worried that just halving the height
> would introduce other breakages.

Hi Laurent,

Thanks a lot, exchanging things this way alone is much appreciated. I'll 
give you detailed feedback on the staging drivers later - I tried 
running them, they probe but still a (gstreamer) stream would not start. 
But most all of your addition make a lot of sense.

Just so you know, to emphasize that once more: I'm still on the nxp 
drivers (yes, they are very similar) just because the ov56 cam works 
with them over here. The main problem I have is that, as soon as I try 
to use a different pixelformat than V4L2_PIX_FMT_YUYV that basically 
nothing works anymore. userspace stops to "be interested" pretty soon.

If I do (wrongly) use that pixelformat, I do get (only) one frame (dma) 
completed, the usual way.

And when I break the ov56 by using a wrong pixelformat in mx6s_capture 
(nxp bridge driver), I get equally get only one frame (dma) completed there.

How can I make this thing use a different pixelformat (by setting the 
media bus format in the sensor driver)?

thanks again for sharing your code early. have a nice rest of the year,


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