Why IMX-MIPI-HDMI can only support up to 720p when use LCDIF on imx8MQ

[xiaowei_zeng]

In "i.MX8MQ EVK Display Selection Guide", it says when use IMX-MIPI-HDMI through LCDIF, it can only support up to 1280x720 60HZ

However, from the datasheet, LCDIF, MIPI and also the adv7535 on IMX-MIPI-HDMI all support 1920x1080 60HZ

So, I wonder the limitiation to 720p is cause by Linux driver or other factors? or some other factor in hardware?

Thanks.

[igorpadykov]

Hi Xiaowei

limitation is internal bandwidth (hardware), so in general one can use more resolution

but underruns may occur, depending on use case.

Best regards
igor

[xiaowei_zeng]

Hi, igor

Thanks your quick response.

You mentioned the limitation is internal hardware bandwidth.

As is known, DCSS->MIPI->IMX-MIPI-HDMI can support 1920x1080 60HZ, but LCDIF->MIPI->IMX-MIPI-HDMI cannot suppot well. Does it means that the limitiation is in LCDIF's bandwidth?

If the limition is the bandwidth, can I use a lower refresh frequency to avoid underflow? e.g. reduce the pixel clock frequency to 1080p 50HZ or lower? or do have other workaround to run 1080p?

Thanks in advance.

BR

Xiaowei

[igorpadykov · Accepted solution]

>If the limition is the bandwidth, can I use a lower refresh frequency to avoid underflow?

yes

Best regards
igor

[Few]

Hi @igorpadykov 

I am currently having problems getting a MIPI-LVDS bridge to work on the i.MX8MM with kernel 5.10.

Is this a limitation of the i.MX or only in combination with the MIPI HDMI bridge?

Thanks!

[xiaowei_zeng]

Thanks igor.

When I set pixel clock to not higher than 120MHz , about 48Hz, the output works well.

BR

Xiaowei