Problems configuring bit-banged I2C

Hi, all!

I use the following patch on my AT91SAM9260-based custom board to configure bit-banged I2C:

index b30aad8..99fc2bd 100644

@ -234,3 +234,46 @@ void reset_phy(void)
#endif
}
#endif
+
+#define GPIO_I2C_SCL AT91_PIN_PA24
+#define GPIO_I2C_SDA AT91_PIN_PA23
+
+void at91sam9260_i2c_init(void)
+{
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_IDR);
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_PUER);
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_PER);
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_MDER);
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_SODR);
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_OER);
+
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_IDR);
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_PUER);
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_PER);
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_MDER);
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_SODR);
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_OER);
+}
+void at91sam9260_i2c_scl(unsigned long bit)
+{
+ if(bit)
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_SODR);
+ else
+ __raw_writel(pin_to_mask(GPIO_I2C_SCL), pin_to_controller(GPIO_I2C_SCL) + PIO_CODR);
+}
+
+void at91sam9260_i2c_sda(unsigned long bit)
+{
+ printf("Setting %u\n", bit);
+ if(bit)
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_SODR);
+ else
+ __raw_writel(pin_to_mask(GPIO_I2C_SDA), pin_to_controller(GPIO_I2C_SDA) + PIO_CODR);
+}
+
+int at91sam9260_i2c_read(void)
+{
+ int c = (__raw_readl(pin_to_controller(GPIO_I2C_SDA) + PIO_PDSR) & pin_to_mask(GPIO_I2C_SDA)) ? 1 : 0;
+ printf("Reading %d\n", c);
+ return c;
+}

index fd9932f..5e66c9e 100644
@@ -85,6 +85,8 @@
 
 #define CONFIG_CMD_NAND		1
 #define CONFIG_CMD_USB		1
+#define CONFIG_CMD_I2C		1
+#define CONFIG_I2C_CMD_TREE	1
 
 /* SDRAM */
 #define CONFIG_NR_DRAM_BANKS		1

@ -192,4 +194,20 @@
#error CONFIG_USE_IRQ not supported
#endif

+/*
+ * Software (bit-bang) I2C driver configuration
+ */
+#define CONFIG_SOFT_I2C 1
+#define CFG_I2C_SPEED 1000000
+#define I2C_INIT at91sam9260_i2c_init()
+
+#define I2C_ACTIVE
+#define I2C_TRISTATE
+#define I2C_SCL(bit) at91sam9260_i2c_scl(bit)
+#define I2C_SDA(bit) at91sam9260_i2c_sda(bit)
+#define I2C_DELAY udelay(2)
+#define I2C_READ at91sam9260_i2c_read()
+#define CFG_I2C_SLAVE 0
+#define DEBUG_I2C
#endif
+

But I'm unable to read proper values from lines - they always return 0s. Any ideas on fixing?
Linux i2c-gpio driver works perfectly.

Thanks a lot,
S.

Why don't you use the gpio function?

void at91sam9260_i2c_init(void)

{
	at91_set_GPIO_periph(AT91_PIN_PA23, 0);
	at91_set_multi_drive(AT91_PIN_PA23, 1);

	at91_set_A_periph(AT91_PIN_PA24, 0);
	at91_set_multi_drive(AT91_PIN_PA24, 1);
}

void at91sam9260_i2c_scl(unsigned long bit)

{
	at91_set_gpio_value(AT91_PIN_PA24, bit);
}

void at91sam9260_i2c_sda(unsigned long bit)

{
	at91_set_gpio_value(AT91_PIN_PA23, bit)
}
int at91sam9260_i2c_read(void)
{
	retrun at91_get_gpio_value(AT91_PIN_PA23);
}
void at91sam9260_i2c_active()
{
	gpio_direction_output(AT91_PIN_PA23, 0);
}

void at91sam9260_i2c_tristate()

{
	gpio_direction_input(AT91_PIN_PA23);
}

Well, I tried to use them but that lead to same result.

Why?

Thanks a lot for your help, but this did not work either. iprobe returns full 0x0 - 0x7f range as devices.
Linux i2c-gpio works properly and returns proper set of devices (0x68, 0x50). Is it me or there's bug somewhere?
I can see output values with oscilloscope. I wonder what happens.

As commented in Linux kernel about i2c_at91, it is very buggy, and I was afraid that it could not work for me at all. i2c-gpio works in Linux. What prevents soft i2c from working ont the same CPU? This stuff is a mystery for me :(

Please try this patch:

http://www.nabble.com/-PATCH--soft_i2c%3A-Pull-SDA-high-before-reading-p17270563.html

You shouldn't need to do anything in the I2C_ACTIVE and I2C_TRISTATE hooks since the PIO is properly configured in open drain mode.

Haavard

Alas, I was unable to make bit-banged I2C to work
even with this patch applied. As I mentioned above, it works in Linux, but I'd like to be able to set time to my RTC from u-boot. I have checked that pins are configured properly from status registers (pull-ups are enabled, multi-drive mode is enabled (open drain), etc.). I could read only zeroes from SDA line in u-boot, and using oscilloscope, I see data on line. I can't find differencies in setup with i2c-gpio from Linux. Any ideas?

Thanks a lot,
S.