Getting data from a rtc device through I2C

Hello hippo,

Thank for replying to my post. I tried your solution but when my board is booting, the i2c-gpio driver reports an error about the i2crtc node as we can see below:

 altera_gpio: /sopc@0/gpio@0x6002630: registered, irq -6
 altera_gpio: /sopc@0/gpio@0x6002640: registered, irq -6
 altera_gpio: /sopc@0/gpio@0x6002650: registered, irq -6
 altera_gpio: /sopc@0/gpio@0x6002660: registered, irq -6
 altera_gpio: /sopc@0/gpio@0x6002670: registered, irq -6
 /sopc@0/i2crtc: invalid GPIO pins, sda=-22/scl=-22
 JFFS2 version 2.2. © 2001-2006 Red Hat, Inc.
 msgmni has been set to 25
 io scheduler noop registered (default)
 ttyAL0 at MMIO 0x6002540 (irq = 2) is a Altera UART
 console  enabled

I looked on the source code and I found that error -22 match the EINVAL errno value (invalid argument) in the i2c-gpio driver's probe function. Extract below:

/* Check if devicetree nodes exist and build platform data */
static int i2c_gpio_of_probe(struct platform_device *pdev,
			     struct i2c_gpio_platform_data *pdata)
{
	struct device_node *np = pdev->dev.of_node;
	const __be32 *prop;
	int sda_pin, scl_pin;
	int len;
	if (!np || of_gpio_count(np) < 2)
		return -ENXIO;
	sda_pin = of_get_gpio_flags(np, 0, NULL);
	scl_pin = of_get_gpio_flags(np, 1, NULL);
	if (sda_pin < 0 || scl_pin < 0) {
		pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
		       np->full_name, sda_pin, scl_pin);
		return -ENXIO;
	}
        
}

So I think, something goes wrong in my device tree. Here is what I did:

-> in my device tree, I replaced the I2C_RTC node (described as a sub node of the sopc)

       sopc@0 {
		ranges;
	# address-cells = < 1 >;
	# size-cells = < 1 >;
		device_type = "soc";
		compatible = "ALTR,avalon", "simple-bus";
		bus-frequency = < 50000000 >;
		
		
		I2C_RTC: gpio@0x6002660 {
			compatible = "i2c-gpio";
			reg = < 0x06002660 0x00000010 >;
			width = < 2 >;	/* width type NUMBER */
			resetvalue = < 0 >;	/* resetValue type NUMBER */
		}; //end gpio@0x6002660 (I2C_RTC)
                
		
	}; //end sopc@0

by: (see bold text)

        sopc@0 {
		ranges;
	# address-cells = < 1 >;
	# size-cells = < 1 >;
		device_type = "soc";
		compatible = "ALTR,avalon", "simple-bus";
		bus-frequency = < 50000000 >;
		
                
                gpio_0: gpio@0x6002660 {
			compatible = "ALTR,pio-10.0","ALTR,pio-1.0";
			reg = < 0x6002660 0x00000010 >;
			//bidir-width = <8>;
			//input-width = <4>;
			width = < 2 >;
			resetvalue = < 0 >;
		# gpio-cells = <2>;
			gpio-controller;
		}; //end gpio (gpio_0)
		i2crtc {
		# address-cells = <1>;
		# size-cells = <0>;
			compatible = "i2c-gpio";
			gpios = < &gpio_0 100 0 /* SDA signal */
					  &gpio_0 99 0 >; /* SCL signal */
			scl-is-output-only;
			rtc@68 {
				compatible = "m41t83";  /* as my rtc chip is an ST m41t83 */
				reg = <0x68>;
			};
		}; //end i2crtc
         }; //end sopc@0

Where am I going wrong?