How to skip CSI0 to SMFC frame?

[yangao]

Hi,

I am trying to take use of the frame skip feature to decrease the frame rate of the camera. In i.MX 6Dual/6Quad Applications Processor Reference Manual, Rev. 4, 09/2017, 37.5.160 CSI0 SKIP Register (IPUx_CSI0_SKIP), CSI0_ID_2_SKIP says,

CSI0 to SMFC Skipping ID.
Data from the CSI0 to the SMFC has an ID associated with it. The ID is received from the MIPI interface.
The skipping mechanism between the CSI0 and the SMFC can be used for only one ID. There is no
skipping for data coming with ID different from the ID programed in this bits
00 - Skipping mechanism is activated on frames with ID equal to 00
01 - Skipping mechanism is activated on frames with ID equal to 01
10 - Skipping mechanism is activated on frames with ID equal to 10
11 - Skipping mechanism is activated on frames with ID equal to 11

What is the ID? Is it the virtual channel? How to configure/know the ID so I can drop the frame from connected camera?

Thanks,

Yan

[igorpadykov]

Hi Yan

one can look at Figure 19-1. CSI2IPU gasket connectivity

i.MX6DQ Reference Manual

https://www.nxp.com/docs/en/reference-manual/IMX6DQRM.pdf 

or Figure 2. Input video routing for i.MX6QP, i.MX6Q, and i.MX6D AN5305

MIPI-CSI2 Peripheral on  i.MX6 MPUs

https://www.nxp.com/docs/en/application-note/AN5305.pdf 

Best regards
igor
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[yangao]

Hi Igor,

Thanks for the prompt reply and it helps.

The Figures are clear and the documents are mostly clear.

However, as to my original question, there is still no explanation for the

CSI0 to SMFC Skipping ID

mentioned in my question. Is it virtual channel ID - the B6 and B7 in Figure 8 in AN5305.pdf?

Thanks,

Yan

[igorpadykov]

Hi Yan

yes it is virtual channel ID

Best regards
igor

[yangao]

Hi Igor,

Clear. Thanks.

Now I have another related question: When I get the IPU CSI_SKIP register value either using devregs or kernel function _ipu_csi_set_skip_smfc, imx6 hangs. What would be the reason?

Thanks,

Yan