i2c: iop: Use GPIO descriptors

The IOP3xx has some elaborate code to directly slam the
GPIO lines multiplexed with I2C down low before enablement,
apparently a workaround for a hardware bug found in the
early chips.

After consulting the developer documentation for IOP80321
and IOP80331 I can clearly see that this may be useful for
IOP80321 family (mach-iop32x) but it is highly dubious for
any 80331 series or later chip: in these chips the lines
are not multiplexed for UARTs.

We convert the code to pass optional GPIO descriptors
and register these only on the 80321-based boards where
it makes sense, optionally obtain them in the driver and
use the gpiod_set_raw_value() to ascertain the line gets
driven low when needed.

The GPIO driver does not give the GPIO chip a reasonable
label so the patch also adds that so that these machine
descriptor tables can be used.

Signed-off-by: Linus Walleij <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Acked-by: Dan Williams <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

arch/arm/include/asm/hardware/iop3xx.h

···
 extern struct platform_device iop3xx_aau_channel;
 extern struct platform_device iop3xx_i2c0_device;
 extern struct platform_device iop3xx_i2c1_device;
+extern struct gpiod_lookup_table iop3xx_i2c0_gpio_lookup;
+extern struct gpiod_lookup_table iop3xx_i2c1_gpio_lookup;
 
 #endif
 

arch/arm/mach-iop32x/em7210.c

···
 #include <linux/platform_device.h>
 #include <linux/i2c.h>
 #include <linux/gpio.h>
+#include <linux/gpio/machine.h>
 #include <mach/hardware.h>
 #include <linux/io.h>
 #include <linux/irq.h>
···
 {
 	register_iop32x_gpio();
 	platform_device_register(&em7210_serial_device);
+	gpiod_add_lookup_table(&iop3xx_i2c0_gpio_lookup);
+	gpiod_add_lookup_table(&iop3xx_i2c1_gpio_lookup);
 	platform_device_register(&iop3xx_i2c0_device);
 	platform_device_register(&iop3xx_i2c1_device);
 	platform_device_register(&em7210_flash_device);

arch/arm/mach-iop32x/glantank.c

···
 #include <linux/i2c.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
+#include <linux/gpio/machine.h>
 #include <mach/hardware.h>
 #include <asm/irq.h>
 #include <asm/mach/arch.h>
···
 static void __init glantank_init_machine(void)
 {
 	register_iop32x_gpio();
+	gpiod_add_lookup_table(&iop3xx_i2c0_gpio_lookup);
+	gpiod_add_lookup_table(&iop3xx_i2c1_gpio_lookup);
 	platform_device_register(&iop3xx_i2c0_device);
 	platform_device_register(&iop3xx_i2c1_device);
 	platform_device_register(&glantank_flash_device);

arch/arm/mach-iop32x/iq31244.c

···
 #include <linux/mtd/physmap.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
+#include <linux/gpio/machine.h>
 #include <mach/hardware.h>
 #include <asm/cputype.h>
 #include <asm/irq.h>
···
 static void __init iq31244_init_machine(void)
 {
 	register_iop32x_gpio();
+	gpiod_add_lookup_table(&iop3xx_i2c0_gpio_lookup);
+	gpiod_add_lookup_table(&iop3xx_i2c1_gpio_lookup);
 	platform_device_register(&iop3xx_i2c0_device);
 	platform_device_register(&iop3xx_i2c1_device);
 	platform_device_register(&iq31244_flash_device);

arch/arm/mach-iop32x/iq80321.c

···
 #include <linux/mtd/physmap.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
+#include <linux/gpio/machine.h>
 #include <mach/hardware.h>
 #include <asm/irq.h>
 #include <asm/mach/arch.h>
···
 static void __init iq80321_init_machine(void)
 {
 	register_iop32x_gpio();
+	gpiod_add_lookup_table(&iop3xx_i2c0_gpio_lookup);
+	gpiod_add_lookup_table(&iop3xx_i2c1_gpio_lookup);
 	platform_device_register(&iop3xx_i2c0_device);
 	platform_device_register(&iop3xx_i2c1_device);
 	platform_device_register(&iq80321_flash_device);

arch/arm/mach-iop32x/n2100.c

···
 #include <linux/reboot.h>
 #include <linux/io.h>
 #include <linux/gpio.h>
+#include <linux/gpio/machine.h>
 #include <mach/hardware.h>
 #include <asm/irq.h>
 #include <asm/mach/arch.h>
···
 static void __init n2100_init_machine(void)
 {
 	register_iop32x_gpio();
+	gpiod_add_lookup_table(&iop3xx_i2c0_gpio_lookup);
 	platform_device_register(&iop3xx_i2c0_device);
 	platform_device_register(&n2100_flash_device);
 	platform_device_register(&n2100_serial_device);

arch/arm/plat-iop/i2c.c

···
 #include <linux/tty.h>
 #include <linux/serial_core.h>
 #include <linux/io.h>
+#include <linux/gpio/machine.h>
 #include <asm/pgtable.h>
 #include <asm/page.h>
 #include <asm/mach/map.h>
···
 #define IRQ_IOP3XX_I2C_0	IRQ_IOP33X_I2C_0
 #define IRQ_IOP3XX_I2C_1	IRQ_IOP33X_I2C_1
 #endif
+
+/*
+ * Each of the I2C busses have corresponding GPIO lines, and the driver
+ * need to access these directly to drive the bus low at times.
+ */
+
+struct gpiod_lookup_table iop3xx_i2c0_gpio_lookup = {
+	.dev_id = "IOP3xx-I2C.0",
+	.table = {
+		GPIO_LOOKUP("gpio-iop", 7, "scl", GPIO_ACTIVE_HIGH),
+		GPIO_LOOKUP("gpio-iop", 6, "sda", GPIO_ACTIVE_HIGH),
+		{ }
+	},
+};
+
+struct gpiod_lookup_table iop3xx_i2c1_gpio_lookup = {
+	.dev_id = "IOP3xx-I2C.1",
+	.table = {
+		GPIO_LOOKUP("gpio-iop", 5, "scl", GPIO_ACTIVE_HIGH),
+		GPIO_LOOKUP("gpio-iop", 4, "sda", GPIO_ACTIVE_HIGH),
+		{ }
+	},
+};
 
 static struct resource iop3xx_i2c0_resources[] = {
 	[0] = {

drivers/gpio/gpio-iop.c

···
 
 	gc->base = 0;
 	gc->owner = THIS_MODULE;
+	gc->label = "gpio-iop";
 
 	return devm_gpiochip_add_data(&pdev->dev, gc, NULL);
 }

drivers/i2c/busses/i2c-iop3xx.c

···
 #include <linux/platform_device.h>
 #include <linux/i2c.h>
 #include <linux/io.h>
-#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 
 #include "i2c-iop3xx.h"
 
···
 
 	/*
 	 * Every time unit enable is asserted, GPOD needs to be cleared
-	 * on IOP3XX to avoid data corruption on the bus.
+	 * on IOP3XX to avoid data corruption on the bus. We use the
+	 * gpiod_set_raw_value() to make sure the 0 hits the hardware
+	 * GPOD register. These descriptors are only passed along to
+	 * the device if this is necessary.
 	 */
-#if defined(CONFIG_ARCH_IOP32X) || defined(CONFIG_ARCH_IOP33X)
-	if (iop3xx_adap->id == 0) {
-		gpio_set_value(7, 0);
-		gpio_set_value(6, 0);
-	} else {
-		gpio_set_value(5, 0);
-		gpio_set_value(4, 0);
-	}
-#endif
+	if (iop3xx_adap->gpio_scl)
+		gpiod_set_raw_value(iop3xx_adap->gpio_scl, 0);
+	if (iop3xx_adap->gpio_sda)
+		gpiod_set_raw_value(iop3xx_adap->gpio_sda, 0);
+
 	/* NB SR bits not same position as CR IE bits :-( */
 	iop3xx_adap->SR_enabled =
 		IOP3XX_ISR_ALD | IOP3XX_ISR_BERRD |
···
 		ret = -ENOMEM;
 		goto free_adapter;
 	}
+
+	adapter_data->gpio_scl = devm_gpiod_get_optional(&pdev->dev,
+							 "scl",
+							 GPIOD_ASIS);
+	if (IS_ERR(adapter_data->gpio_scl))
+		return PTR_ERR(adapter_data->gpio_scl);
+	adapter_data->gpio_sda = devm_gpiod_get_optional(&pdev->dev,
+							 "sda",
+							 GPIOD_ASIS);
+	if (IS_ERR(adapter_data->gpio_sda))
+		return PTR_ERR(adapter_data->gpio_sda);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res) {

drivers/i2c/busses/i2c-iop3xx.h

···
 	spinlock_t lock;
 	u32 SR_enabled, SR_received;
 	int id;
+	struct gpio_desc *gpio_scl;
+	struct gpio_desc *gpio_sda;
 };
 
 #endif /* I2C_IOP3XX_H */