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How to set a LCDIFx_THRES registers in i.MX7D

Question asked by ko-hey on Sep 14, 2017
Latest reply on Oct 10, 2017 by ko-hey
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Hi all

 

I have a question about LCDIFx_THRES registers in i.MX7D.

My customer have a problem with LCDIF.

MIPI-DSI output is flickering and have underflow error in LCDIF.

 

We think LCDIFx_THRES registers can be useful to resolve this issue setting a FASTCLOCK and PANIC register.

In this situation, I have questions for the register.

 

Q1.

The description of FASTCLOCK is as below.

 

"This value should be set to a value of pixels, from 0 to 511. When the number of pixels in the input pixel
FIFO is LESS than this value, the fast clock control output will be raised. This signal can be used to
reduce the system bus clock frequency to save power during horizontal or vertical blanking intervals. This
value should also be programmed to a value that is greater than the "PANIC" threshold value. This will
allow a faster clock to recover the number of pixels in the FIFO before a "panic" level is encountered."

 

What is the bus clock which is line 3 ?

Could you specify the clock in figure 5-2. i.MX7Dual PLL and PFD of reference manual ?

 

 

Q2.

Here is the description of PANIC bit.

 

"This value should be set to a value of pixels from 0 to 511. When the number of pixels in the input pixel
FIFO is less than this value, the internal panic control output will be raised. This signal can be used to
raise the access eLCDIF's access priority."

 

How can user decide the value ?

 

My customer set it to FASTCLOCK to 511 and PANIC to 510 by using following parameter.

HW_LCDIF_LCDIF1_THRES_SET(0x01FF01FE);//priority threshold register

 

Do you have recommendation ?

 

 

 

Ko-hey

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