ARM: OMAP3: Make I2C bus 2 configurable for BeagleBoard

I2C2 at BeagleBoard is connected to expansion connector, i.e. unused if nothing is connected to this connector. As internal OMAP3 pull up resistors are not strong enough, enabled but unused I2C2 bus results in error messages (e.g. I2C timeouts). I2C2 should be enabled only if something is connected to I2C2 at board's expansion connector and this extension has additional pull up resistors for I2C2 bus.

- Add configuration option for this
- Use configuration option in board-omap3beagle
- Ensure correct pin mux if I2C2 is enabled, independent of settings done by bootloader
- While being there, add OMAP3 to OMAP I2C help text

Subject: ARM: OMAP3: Make I2C bus 2 configurable for BeagleBoard

From: Dirk Behme <[email protected]>

I2C2 at BeagleBoard is connected to expansion connector, i.e. unused if nothing is connected to this connector. As internal OMAP3 pull up resistors are not strong enough, enabled but unused I2C2 bus results in error messages (e.g. I2C timeouts). I2C2 should be enabled only if something is connected to I2C2 at board's expansion connector and this extension has additional pull up resistors for I2C2 bus.

- Add configuration option for this
- Use configuration option in board-omap3beagle
- Ensure correct pin mux if I2C2 is enabled, independent of settings done by bootloader.
- While being there, add OMAP3 to OMAP I2C help text

---

Index: linux-beagle/arch/arm/mach-omap2/board-omap3beagle.c
===================================================================
@@ -40,7 +40,9 @@ static struct omap_uart_config omap3_bea
 static int __init omap3_beagle_i2c_init(void)
 {
 	omap_register_i2c_bus(1, 2600, NULL, 0);
+#ifdef CONFIG_I2C2_OMAP_BEAGLE
 	omap_register_i2c_bus(2, 400, NULL, 0);
+#endif
 	omap_register_i2c_bus(3, 400, NULL, 0);
 	return 0;
 }

Index: linux-beagle/arch/arm/mach-omap2/mux.c
===================================================================
@@ -231,10 +231,12 @@ MUX_CFG_34XX("K21_34XX_I2C1_SCL", 0x1ba,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
 MUX_CFG_34XX("J21_34XX_I2C1_SDA", 0x1bc,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
+#ifdef CONFIG_I2C2_OMAP_BEAGLE
 MUX_CFG_34XX("AF15_34XX_I2C2_SCL", 0x1be,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
 MUX_CFG_34XX("AE15_34XX_I2C2_SDA", 0x1c0,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
+#endif
 MUX_CFG_34XX("AF14_34XX_I2C3_SCL", 0x1c2,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
 MUX_CFG_34XX("AG14_34XX_I2C3_SDA", 0x1c4,

Index: linux-beagle/drivers/i2c/busses/Kconfig
===================================================================
@@ -332,10 +332,27 @@ config I2C_OMAP
 	default y if MACH_OMAP_H3 || MACH_OMAP_OSK
 	help
 	  If you say yes to this option, support will be included for the
-	  I2C interface on the Texas Instruments OMAP1/2 family of processors.
-	  Like OMAP1510/1610/1710/5912 and OMAP242x.
+	  I2C interface on the Texas Instruments OMAP1/2/3 family of
+	  processors.
+	  Like OMAP1510/1610/1710/5912, OMAP242x, OMAP34x and OMAP35x.
 	  For details see http://www.ti.com/omap.
 
+config I2C2_OMAP_BEAGLE
+	bool "Enable I2C2 for OMAP3 BeagleBoard"
+	depends on ARCH_OMAP && MACH_OMAP3_BEAGLE
+	select OMAP_MUX
+	default n
+	help
+	  Say Y here if you want to enable I2C bus 2 at OMAP3 based
+	  BeagleBoard.
+	  I2C2 at BeagleBoard is connected to expansion connector, i.e. unused
+	  if nothing is connected to this connector. As internal OMAP3 pull up
+	  resistors are not strong enough, enabled but unused I2C2 bus results
+	  in error messages (e.g. I2C timeouts). Enable this only if you have
+	  something connected to I2C2 at board's expansion connector and this
+	  extension has additional pull up resistors for I2C2 bus.
+
+
 config I2C_PARPORT
 	tristate "Parallel port adapter"
 	depends on PARPORT

Why this CONFIG_I2C2_OMAP_BEAGLE in mux.c?

Jarkko

@@ -231,10 +231,12 @@ MUX_CFG_34XX("K21_34XX_I2C1_SCL", 0x1ba,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
 MUX_CFG_34XX("J21_34XX_I2C1_SDA", 0x1bc,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
+#ifdef CONFIG_I2C2_OMAP_BEAGLE
 MUX_CFG_34XX("AF15_34XX_I2C2_SCL", 0x1be,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
 MUX_CFG_34XX("AE15_34XX_I2C2_SDA", 0x1c0,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
+#endif
 MUX_CFG_34XX("AF14_34XX_I2C3_SCL", 0x1c2,
 		OMAP34XX_MUX_MODE0 | OMAP34XX_PIN_INPUT_PULLUP)
 MUX_CFG_34XX("AG14_34XX_I2C3_SDA", 0x1c4,

Because bootloader, e.g. uboot, might have set other mux for these pins, e.g. GPIO168 and GPIO183.

Then, if CONFIG_MUX is enabled but I2C2 isn't, don't touch the pin mux done by bootloader. But if I2C2 is enabled, make sure that the correct mux settings are done independent of bootloader.

Do you think this is wrong?

Thanks

Dirk