[U-Boot-Users] [AT91] Problems configuring bit-banged I2C

[Sergey Lapin]

Hi, all!

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

diff --git a/board/atmel/at91sam9260ek/at91sam9260ek.c b/board/atmel/at91sam9260ek/at91sam9260ek.c
index b30aad8..99fc2bd 100644
--- a/board/atmel/at91sam9260ek/at91sam9260ek.c
+++ b/board/atmel/at91sam9260ek/at91sam9260ek.c
@ -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;
+}
diff --git a/include/configs/at91sam9260ek.h b/include/configs/at91sam9260ek.h
index fd9932f..5e66c9e 100644
--- a/include/configs/at91sam9260ek.h
+++ b/include/configs/at91sam9260ek.h
@@ -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.

-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2008.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
_______________________________________________
U-Boot-Users mailing list
U-Boot...@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/u-boot-users

[Jean-Christophe PLAGNIOL-VILLARD]

On 03:36 Sat 24 May , Sergey Lapin wrote:
> Hi, all!
>
> I use the following patch on my AT91SAM9260-based custom board to
> configure bit-banged I2C:
>
> diff --git a/board/atmel/at91sam9260ek/at91sam9260ek.c b/board/atmel/at91sam9260ek/at91sam9260ek.c
> index b30aad8..99fc2bd 100644
> --- a/board/atmel/at91sam9260ek/at91sam9260ek.c
> +++ b/board/atmel/at91sam9260ek/at91sam9260ek.c
> @ -234,3 +234,46 @@ void reset_phy(void)
> #endif
> }
> #endif

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);

}
> diff --git a/include/configs/at91sam9260ek.h b/include/configs/at91sam9260ek.h
> index fd9932f..5e66c9e 100644
> --- a/include/configs/at91sam9260ek.h
> +++ b/include/configs/at91sam9260ek.h
> @@ -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 at91sam9260_i2c_active()
#define I2C_TRISTATE at91sam9260_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
> +

I sync it will be better to use the hardware stack which is not too
complicate to implement

Best Regards,
J.

[Haavard Skinnemoen]

Sergey Lapin <sla...@fan.ossfans.org> wrote:
> But I'm unable to read proper values from lines - they always
> return 0s. Any ideas on fixing?
> Linux i2c-gpio driver works perfectly.

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

[Sergey Lapin]

On Sat, May 24, 2008 at 05:24:00PM +0200, Haavard Skinnemoen wrote:
> Sergey Lapin <sla...@fan.ossfans.org> wrote:
> > But I'm unable to read proper values from lines - they always
> > return 0s. Any ideas on fixing?
> > Linux i2c-gpio driver works perfectly.
>
> 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.

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.

[Sergey Lapin]

> Why don't you use the gpio function?

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

> > +
> 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);

Why?

> 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);
> }

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.

>
> I sync it will be better to use the hardware stack which is not too
> complicate to implement

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 :(

[yehudaa...@gmail.com]

Hi

For anyone that such problem -

I already encountered such problem.

The problem is that to read input PIO pin, the PMC clock for that PIO port must be enabled at PMC_PCER .

Add (for PIOA):

    {

       at91_pmc_t *pmc = (at91_pmc_t *) ATMEL_BASE_PMC;

       //enable pmc pioa peripheral clock to be able read io pins !!!!

    writel(1 << ATMEL_ID_PIOA, &pmc->pcer);

      } 

This will solve the issue.

Yehuda