i2c: at91: add new driver

This driver has the following properties compared to the old driver:
1. Support for multiple interfaces.
2. Interrupt driven I/O as opposed to polling/busy waiting.
3. Support for _one_ repeated start (Sr) condition, which is enough
   for most real-world applications including all SMBus transfer types.
   (The hardware does not support issuing arbitrary Sr conditions on the
    bus.)

testing: SoC: at91sam9g45
	 - BQ20Z80 battery SMBus client.
	 - on a 2.6.38 kernel with several i2c clients (temp-sensor,
	   audio-codec, touchscreen-controller, w1-bridge, io-expanders)

Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Tested-by: Hubert Feurstein <h.feurstein@gmail.com>
Tested-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>

[wsa: squashed with the following patches from Ludovic to have some flaws
fixed:
        i2c: at91: use managed resources
        i2c: at91: add warning about transmission issues for some devices
        i2c: at91: use an id table for SoC dependent parameters
]

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>

arch/arm/mach-at91/at91rm9200.c

@@ -187,7 +187,7 @@ static struct clk_lookup periph_clocks_lookups[] = {
 	CLKDEV_CON_DEV_ID("pclk", "ssc.0", &ssc0_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.1", &ssc1_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.2", &ssc2_clk),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c", &twi_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91rm9200", &twi_clk),
 	/* fake hclk clock */
 	CLKDEV_CON_DEV_ID("hclk", "at91_ohci", &ohci_clk),
 	CLKDEV_CON_ID("pioA", &pioA_clk),

arch/arm/mach-at91/at91rm9200_devices.c

@@ -495,7 +495,7 @@ static struct resource twi_resources[] = {
 };
 
 static struct platform_device at91rm9200_twi_device = {
-	.name		= "at91_i2c",
+	.name		= "i2c-at91rm9200",
 	.id		= -1,
 	.resource	= twi_resources,
 	.num_resources	= ARRAY_SIZE(twi_resources),

arch/arm/mach-at91/at91sam9260.c

@@ -211,7 +211,8 @@ static struct clk_lookup periph_clocks_lookups[] = {
 	CLKDEV_CON_DEV_ID("t1_clk", "atmel_tcb.1", &tc4_clk),
 	CLKDEV_CON_DEV_ID("t2_clk", "atmel_tcb.1", &tc5_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.0", &ssc_clk),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c", &twi_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9260", &twi_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9g20", &twi_clk),
 	/* more usart lookup table for DT entries */
 	CLKDEV_CON_DEV_ID("usart", "fffff200.serial", &mck),
 	CLKDEV_CON_DEV_ID("usart", "fffb0000.serial", &usart0_clk),

arch/arm/mach-at91/at91sam9260_devices.c

@@ -503,14 +503,20 @@ static struct resource twi_resources[] = {
 };
 
 static struct platform_device at91sam9260_twi_device = {
-	.name		= "at91_i2c",
 	.id		= -1,
 	.resource	= twi_resources,
 	.num_resources	= ARRAY_SIZE(twi_resources),
 };
 
 void __init at91_add_device_i2c(struct i2c_board_info *devices, int nr_devices)
 {
+	/* IP version is not the same on 9260 and g20 */
+	if (cpu_is_at91sam9g20()) {
+		at91sam9260_twi_device.name = "i2c-at91sam9g20";
+	} else {
+		at91sam9260_twi_device.name = "i2c-at91sam9260";
+	}
+
 	/* pins used for TWI interface */
 	at91_set_A_periph(AT91_PIN_PA23, 0);		/* TWD */
 	at91_set_multi_drive(AT91_PIN_PA23, 1);

arch/arm/mach-at91/at91sam9261.c

@@ -178,7 +178,8 @@ static struct clk_lookup periph_clocks_lookups[] = {
 	CLKDEV_CON_DEV_ID("pclk", "ssc.1", &ssc1_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.2", &ssc2_clk),
 	CLKDEV_CON_DEV_ID("hclk", "at91_ohci", &hck0),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c", &twi_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9261", &twi_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9g10", &twi_clk),
 	CLKDEV_CON_ID("pioA", &pioA_clk),
 	CLKDEV_CON_ID("pioB", &pioB_clk),
 	CLKDEV_CON_ID("pioC", &pioC_clk),

arch/arm/mach-at91/at91sam9261_devices.c

@@ -317,14 +317,20 @@ static struct resource twi_resources[] = {
 };
 
 static struct platform_device at91sam9261_twi_device = {
-	.name		= "at91_i2c",
 	.id		= -1,
 	.resource	= twi_resources,
 	.num_resources	= ARRAY_SIZE(twi_resources),
 };
 
 void __init at91_add_device_i2c(struct i2c_board_info *devices, int nr_devices)
 {
+	/* IP version is not the same on 9261 and g10 */
+	if (cpu_is_at91sam9g10()) {
+		at91sam9261_twi_device.name = "i2c-at91sam9g10";
+	} else {
+		at91sam9261_twi_device.name = "i2c-at91sam9261";
+	}
+
 	/* pins used for TWI interface */
 	at91_set_A_periph(AT91_PIN_PA7, 0);		/* TWD */
 	at91_set_multi_drive(AT91_PIN_PA7, 1);

arch/arm/mach-at91/at91sam9263.c

@@ -193,7 +193,7 @@ static struct clk_lookup periph_clocks_lookups[] = {
 	CLKDEV_CON_DEV_ID("spi_clk", "atmel_spi.0", &spi0_clk),
 	CLKDEV_CON_DEV_ID("spi_clk", "atmel_spi.1", &spi1_clk),
 	CLKDEV_CON_DEV_ID("t0_clk", "atmel_tcb.0", &tcb_clk),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c", &twi_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9260", &twi_clk),
 	/* fake hclk clock */
 	CLKDEV_CON_DEV_ID("hclk", "at91_ohci", &ohci_clk),
 	CLKDEV_CON_ID("pioA", &pioA_clk),

arch/arm/mach-at91/at91sam9263_devices.c

@@ -574,7 +574,7 @@ static struct resource twi_resources[] = {
 };
 
 static struct platform_device at91sam9263_twi_device = {
-	.name		= "at91_i2c",
+	.name		= "i2c-at91sam9260",
 	.id		= -1,
 	.resource	= twi_resources,
 	.num_resources	= ARRAY_SIZE(twi_resources),

arch/arm/mach-at91/at91sam9g45.c

@@ -237,8 +237,8 @@ static struct clk_lookup periph_clocks_lookups[] = {
 	CLKDEV_CON_DEV_ID("spi_clk", "atmel_spi.1", &spi1_clk),
 	CLKDEV_CON_DEV_ID("t0_clk", "atmel_tcb.0", &tcb0_clk),
 	CLKDEV_CON_DEV_ID("t0_clk", "atmel_tcb.1", &tcb0_clk),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c.0", &twi0_clk),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c.1", &twi1_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9g10.0", &twi0_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9g10.1", &twi1_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.0", &ssc0_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.1", &ssc1_clk),
 	CLKDEV_CON_DEV_ID(NULL, "atmel-trng", &trng_clk),

arch/arm/mach-at91/at91sam9g45_devices.c

@@ -653,7 +653,7 @@ static struct resource twi0_resources[] = {
 };
 
 static struct platform_device at91sam9g45_twi0_device = {
-	.name		= "at91_i2c",
+	.name		= "i2c-at91sam9g10",
 	.id		= 0,
 	.resource	= twi0_resources,
 	.num_resources	= ARRAY_SIZE(twi0_resources),
@@ -673,7 +673,7 @@ static struct resource twi1_resources[] = {
 };
 
 static struct platform_device at91sam9g45_twi1_device = {
-	.name		= "at91_i2c",
+	.name		= "i2c-at91sam9g10",
 	.id		= 1,
 	.resource	= twi1_resources,
 	.num_resources	= ARRAY_SIZE(twi1_resources),

arch/arm/mach-at91/at91sam9rl.c

@@ -186,8 +186,8 @@ static struct clk_lookup periph_clocks_lookups[] = {
 	CLKDEV_CON_DEV_ID("t2_clk", "atmel_tcb.0", &tc2_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.0", &ssc0_clk),
 	CLKDEV_CON_DEV_ID("pclk", "ssc.1", &ssc1_clk),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c.0", &twi0_clk),
-	CLKDEV_CON_DEV_ID(NULL, "at91_i2c.1", &twi1_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9g20.0", &twi0_clk),
+	CLKDEV_CON_DEV_ID(NULL, "i2c-at91sam9g20.1", &twi1_clk),
 	CLKDEV_CON_ID("pioA", &pioA_clk),
 	CLKDEV_CON_ID("pioB", &pioB_clk),
 	CLKDEV_CON_ID("pioC", &pioC_clk),

arch/arm/mach-at91/at91sam9rl_devices.c

@@ -346,7 +346,7 @@ static struct resource twi_resources[] = {
 };
 
 static struct platform_device at91sam9rl_twi_device = {
-	.name		= "at91_i2c",
+	.name		= "i2c-at91sam9g20",
 	.id		= -1,
 	.resource	= twi_resources,
 	.num_resources	= ARRAY_SIZE(twi_resources),

drivers/i2c/busses/Kconfig

@@ -290,18 +290,21 @@ comment "I2C system bus drivers (mostly embedded / system-on-chip)"
 
 config I2C_AT91
 	tristate "Atmel AT91 I2C Two-Wire interface (TWI)"
-	depends on ARCH_AT91 && EXPERIMENTAL && BROKEN
+	depends on ARCH_AT91 && EXPERIMENTAL
 	help
 	  This supports the use of the I2C interface on Atmel AT91
 	  processors.
 
-	  This driver is BROKEN because the controller which it uses
-	  will easily trigger RX overrun and TX underrun errors.  Using
-	  low I2C clock rates may partially work around those issues
-	  on some systems.  Another serious problem is that there is no
-	  documented way to issue repeated START conditions, as needed
+	  A serious problem is that there is no documented way to issue
+	  repeated START conditions for more than two messages, as needed
 	  to support combined I2C messages.  Use the i2c-gpio driver
-	  unless your system can cope with those limitations.
+	  unless your system can cope with this limitation.
+
+	  Caution! at91rm9200, at91sam9261, at91sam9260, at91sam9263 devices
+	  don't have clock stretching in transmission mode. For that reason,
+	  you can encounter underrun issues causing premature stop sendings if
+	  the latency to fill the transmission register is too long. If you
+	  are facing this situation, use the i2c-gpio driver.
 
 config I2C_AU1550
 	tristate "Au1550/Au1200/Au1300 SMBus interface"

drivers/i2c/busses/Makefile

@@ -28,6 +28,7 @@ obj-$(CONFIG_I2C_HYDRA)		+= i2c-hydra.o
 obj-$(CONFIG_I2C_POWERMAC)	+= i2c-powermac.o
 
 # Embedded system I2C/SMBus host controller drivers
+obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
 obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o
 obj-$(CONFIG_I2C_BLACKFIN_TWI)	+= i2c-bfin-twi.o
 obj-$(CONFIG_I2C_CPM)		+= i2c-cpm.o