topic Re: Problem LVDS pixel clock on IMX8MP in i.MX Processors

Problem LVDS pixel clock on IMX8MP

domenicoacri — Mon, 07 Mar 2022 11:01:19 GMT

Hi, I'm trying to connect an LVDS display on imx8mp. (Linux 5.10.35_2.0.0)

These are the timing of my LCD, pixel-clock at 64MHz as below the code,

but it doesen't seem to work.

panel-timing {

clock-frequency = <65000000>;

hactive = <1024>;

vactive = <600>;

hsync-len = <136>;

hfront-porch = <20>;

hback-porch = <160>;

vfront-porch = <3>;

vback-porch = <29>;

vsync-len = <6>;

};

The output frequency is fixed at 74.2 MHz.

It would appear set in the imx8mp-ldb.c driver.

How can this parameter be changed from the device tree?

Best Regards

Domenico Acri

Re: Problem LVDS pixel clock on IMX8MP

joanxie — Wed, 09 Mar 2022 03:42:56 GMT

you can refer to the driver of ldb

https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/gpu/drm/imx/imx8mp-ldb.c?h=lf-5.10.y

check the function "imx8mp_ldb_encoder_atomic_check, you need comment the fixed clock, but not all of clock can be supported, but I checked, the 65M can be supported

Re: Problem LVDS pixel clock on IMX8MP

domenicoacri — Fri, 11 Mar 2022 15:48:48 GMT

Hi,

thank you very much for the prompt reply.

Yes, I had also changed that function and it seems to work.

The thing I was interested in knowing was,

what are the supported frequencies and where they are defined.

Best Regards

Domenico Acri

Re: Problem LVDS pixel clock on IMX8MP

joanxie — Tue, 15 Mar 2022 05:23:18 GMT

lvds uses video_pll1, pls refer to the clock source code:

"https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/clk/imx/clk-imx8mp.c?h=lf-5.10.y"
"https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/clk/imx/clk-pll14xx.c?h=lf-5.10.y"

Re: Problem LVDS pixel clock on IMX8MP

embdev1 — Thu, 07 Apr 2022 06:36:38 GMT

Can you please tell me the location of panel-timing structure? I am searching for this to modify timing settings of my LVDS display. Thanks in advance.

Re: Problem LVDS pixel clock on IMX8MP

joanxie — Mon, 11 Apr 2022 09:31:47 GMT

you can add it in the imx8mp dts file