What is the use case of "decoder_boot" and "encoder_boot" ?

[Raana]

Dear Team,

I'm using 1GB DDR3 on our iMx8DX6 based custom board. Kernel version is, L4.14.62.

During analysis of current DDR/memory usage, we observed that Memtotal available is around 700 MB.

There the static allocation like shown in below line in dtsi file

               decoder_boot: decoder_boot@0x84000000 {

                        no-map;

                        reg = <0 0x84000000 0 0x2000000>;

                };

                encoder_boot: encoder_boot@0x86000000 {

                        no-map;

                        reg = <0 0x86000000 0 0x2000000>;

                };

etc...

mentioned in the structure of "reserved-memory" in "arch/arm64/boot/dts/freescale/fsl-imx8dx.dtsi" file.

We are not using Graphics & Framebuffer and still ~300MB is getting consumed by Kernel and with reserved/other components (i.e Memtotal is around 700MB – Checked using meminfo and free command).

We have modified the reserved size allocated for decoder_boot and encoder_boot and tested with this modified device tree file (dtb).

We could observe the increase in value of "MemTotal" (Memtotal confirmed using meminfo and free command).

Our observation is above fields are not affecting the board normal functionality.

Whether this "decoder_boot","encoder_boot","decoder_rpc","encoder_rpc" and "decoder_str" is really need to be reserved as we do not need to configure Graphics & Framebuffer ?

Please anybody can provide the exact use case of this field.

Best Regards,

J.P.Raja

[igorpadykov]

Hi Raja

these settings are for i.MX8DX VPU modules (encoder, decoder) described in sect.17.1.1.2 VPU

i.MX 8DualXPlus/8QuadXPlus Applications Processor Reference Manual

linux configuration in : linux/arch/arm64/boot/dts/freescale/fsl-imx8dx.dtsi

fsl-imx8dx.dtsi\freescale\dts\boot\arm64\arch - linux-imx - i.MX Linux kernel 

and sect.6.7.3 Menu Configuration Options attached Linux Manual.

It can be disabled if not used.

Best regards
igor
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[Raana]

Hi Igor,

I have already disabled all the configurations inside the "Device Drivers >MXC support drivers". But, No improvement.

So, now I have reduced the size of that. Like,

decoder_boot: decoder_boot@0x84000000 {
                        no-map;
                        reg = <0 0x84000000 0 0x4>;
};

encoder_boot: encoder_boot@0x86000000 {
                        no-map;
                        reg = <0 0x86000000 0 0x4>;
};

Reserved memory size also reduced now. Is this okay ?

Note: It was throwing error when I set as 0x0. That's why I set 0x4.

Thank You.

Best Regards,

J.P.Raja

[igorpadykov]

Hi Raja

one can try latest Linux L4.19.35_1.1.0
https://source.codeaurora.org/external/imx/linux-imx/tree/?h=imx_4.19.35_1.1.0

Best regards
igor

[Raana]

Hi Igor,

Thanks for your reply. I'm unable to download the document (page not found).

Thank You.

Best Regards,

J.P.Raja