iMX7D power reduction methods in suspend mode

[bensonyoung]

Hello,

Our product will be battery powered under certain operating condition.

In order to conserve power, I will be bringing the processor into suspend mode with command

echo mem > /sys/power/state

I noticed some GPIO is brought to a different state. Is it defined in the iomuxc_lpsr structure within the DTS?

&iomuxc_lpsr {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_lte_psm>;

...

}

Is there any way that I can define/control GPIO behaviour during processor suspend mode, so I can reduce possible DC leakage current.

If I have unused functionality like MIPI, HDMI, SPI etc. Is it possible for me to shut them down? using DTS? or dynamically?

thank you

[bensonyoung]

Hi Igor,

Thank you for your response.

Is there any sample code? The setting code is in assembly and I don't see any tweaks to the GPIO control registers.

On our design, quite a few circuitry uses the GPIO pins belonging to the EPDC controller.

However, I am seeing different behaviour on the pins during CPU suspend. Most pins will be in the low logic, when the CPU is placed in suspend (echo mem > /sys/power/state), but GPIO_EPDC_SDOE and GPIO_EPDC_GDCLK appears to be in logic high or at lease high-impedence(input) state.

why is it so?

please comment.

[igorpadykov]

Hi Benson

I am afraid it is not possible to configure it in dts file,

one can add gpio setting code in linux/arch/arm/mach-imx/suspend-imx7.S

suspend-imx7.S\mach-imx\arm\arch - linux-imx - i.MX Linux kernel 

Best regards
igor
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